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KINEMATICS
from Femosky110 on 06/12/2020 01:49 PMKinematics
The concept of Kinematics is the study of motion without the force causing them and the mass of the body. Suppose a body of mass 2kg is pulled a distance of 10m by a force of 5N; kinematics studies only the movement in a giving direction without concern on the 5N force or the 2kg mass of the body.
The motion of a body can either be in any of these forms:
1. Random: Example is gaseous particles,
2. Translational: Example is a moving car,
3. Rotational: Example is a ceiling fan,
4. Oscillatory: Example is swinging pendulum.
Straight Line Motion (SLM)
This is the motion of a body in a straight line. There are four parameters involved in the study of this motion of a body in a straight line. They are Displacement or Distance, Velocity, Acceleration and Time.
Displacement
This is the distance travelled in a specified direction. It is the shortest distance between two points. In kinematics it is represented with (s) and is mathematically related to velocity thus:
s = vt
Where: s = displacement
v = velocity
t = time
The unit of displacement is metre (m).
Example 1
A car with a uniform velocity of 10 m/s left Enugu at 10:00 am and arrived Nsukka at 10:30 am. Calculate its displacement.
Solution:
First let's write down the terms given to us. We have:
v = 10 m/s
T = (10:30 – 10:00) = 30 minutes, Note: we need to further change this time to be in seconds. So 30 minutes would be:
(30 x 60) sec = 1800 s.
So from the formula, we have that
s = vt
s = 10 x 1800
s = 18000 m.
Displacement and Distance
Most often students who are new to physics find it very difficult to understand the difference between displacement and distance. We will quickly highlight the differences before we continue with the next section.
Although these two quantities appear to be similar but displacement is a vector quantity and by so it is direction- aware while distance is a scalar quantity.
To fully understand the terms scalar and vector in physics, we will go ahead and define the meaning of these terms.
Scalars are quantities that have only magnitude
Vectors are quantities that have both magnitude and direction
A simple illustration of distance and displacement example is; if a man travels in a rectangular path from a starting point along the path and ends on the same spot he started, the displacement in this situation is zero while the distance is the length of the rectangular path from the starting point to the end point.
physics
It is also important to note that when an object changes direction and start moving in opposite direction it will effectively cancel its initial displacement.
Distance can be measured by one of the following measuring tools and its unit of measurement is in meters.
Use of string
Metre rule
Vernier callipers
Micrometre screw gauge
Velocity
Velocity is speed measured in a specified direction. Many misunderstand Speed to be Velocity. In Physics, the two mean different things. Speed is the rate of change of distance with time. Velocity is a vector quantity (i.e. it has both magnitude and direction) while speed is a scalar quantity (it has magnitude but no direction) - we shall treat it in the next tutorial.
The unit of velocity is metre per second (m/s). Mathematically:
Velocity (v) = s/t
Where s = displacement, t = time.
Uniform velocity: A body is said to be in a uniform velocity when the ration (s/t) is constant - unchanging.
Average Velocity (aV): Average velocity is the total distance travelled (Stotal ) divided by the total time taken (Ttotal).
aV = Stotal /Ttotal
Example 1
Calculate the velocity of a car that covered a distance of 250 metres in 25 seconds.
Solution:
We write down the given terms as always:
S = 250m
T = 25s
v = s/t
v = 250/25
v = 10 m/s.
Acceleration
Acceleration is the rate of change of velocity with time. The unit of acceleration is metre per second squared (m/s2). Acceleration like velocity is a vector quantity that is why it is wrong to think that acceleration means the rate of change of speed with time. Mathematically Acceleration (a) is:
physics
a = v/t
Where v = velocity, t = time.
Uniform acceleration: If the rate of change of velocity is constant, the acceleration is said to be uniform. This implies that:
a = v/t = constant.
If the velocity of a body is increasing with time, it is said to be accelerating, but if the velocity of a body is decreasing with time, it is said to be retarding or decelerating or experiencing retardation or deceleration. And then in such a case, it is important we notice the acceleration is said to be negative.
Example I
A body rolled from point X to point Y in 2 seconds with a velocity of 5m/s. Calculate the acceleration of the car.
Solution:
First, we note down our terms,
t = 2 s
v = 5 m/s
From the formula a = v/t
a = 5/2
a = 2.5 m/s2
The Equation of Motion
Deriving the equations of motion, it was noticed that if a body starts with initial velocity 'u' accelerates uniformly along a straight line with acceleration 'a' and covers a distance 's' in a time 't' when its velocity reaches a final value 'v', then the distance 's' covered is given by s = average velocity times time.
s = u – v x t ......... (Equation 1)
Also by definition, acceleration 'a' = rate of change of velocity and since 'a' is constant we will have
a = (v-u)/t = v = u + at ............... (Equation II)
Eliminating t from (Equation I) and (Equation II), we fined
v2 = u2 + 2as ......... (Equation III)
Eliminating 'v' from (Equation I) and (Equation II), we find
s = ut + 1/2 at2 ......... ( Equation IV)
Note:
These four equations of motion are used in solving problems associated with uniformly accelerated motion. When using them, the following points should be noted.
I. Ensure that all the units match. i.e., velocity in m/s, distance in m, acceleration in m/s2 and time in s.
II. Each of the equations contains four of the five variables u, v, s, a, t. The values of three are normally given and the values of one or both unknowns are required to be found.
III. To determine which equation to use in solving a particular problem,
(a) Note down the given variables,
(b) Note down the required variable,
(c) Note down the un-given variable
(d) Then the equation to use is the one that does NOT contain the un-given variable.
Hint:
Equation I does not contain a
Equation II does not contain s
Equation III does not contain t
Equation IV does not contain v
IV. Note the conversion formulae: 1km/h = 1000/ (60 x 60) m/s OR 36km/h = 10m/s OR 1m/s = 3.6km/h.
V. Do not confuse s for distance with s the unit of time.
Example I
A car moves from rest with an acceleration of 0.2m/s2. Find its velocity when it has moved a distance of 50m.
Solution:
We note down the given variables, which are:
a = 0.2m/s2
s = 50m
The required variable is 'v' and
The un-given variable is t and the equation that doesn't contain t is Equation III. So we use Equation III.
v2 = u2 + 2as
We should also bear in mind that the initial velocity u of a moving body which started at rest is zero.
So with that now, our u here will be 0m/s.
v2 = 02 + 2 x 0.2 x 50
v = √ (0 + 2 x 0.2 x 50)
v = √ 20
v = 4.47m/s.
Example II
A car is uniformly retarded and brought to rest from a velocity of 36km/h in 5sec. Find:
(a) Its retardation
(b) The distance covered during this period.
Solution:
Like before, write down the variables. Then we have
v = 36km/h
t = 5s
s = ?
(
a) First, we should notice that by retardation, we are required to find the acceleration. Then the formula for acceleration is
a = v/t
and here we have v = 36km/h, we will need to change it to m/s before we proceed. So 36km/h = (36 x 1000) / (60 x 60) = 36000/3600 = 10m/s
Therefore we now have
a = 10/5
a= 2m/s2
(b) Now we have the acceleration, we need to find the distance covered, so we use (Equation IV). And I need someone to tell us why we should use Equation IV.
So from equation IV
s = ut + 1/2at2
Note: initial velocity (u) in this case is zero, then
Then s = 0 + 1/2 x 2 x 25
s = 25 m.
Now let's have one or two problem set for you to solve. Please try your hand on these questions. It will help you to fully understand this topic. Once you are done with it you can jump over to the next tutorial.
Question I
A train slows from 108km/h with a uniform retardation of 5m/s2. How long will it take to reach 18km/h?
Question II
What is the distance covered in question 1?
You should try and solve the problem. Practising is a good way of learning.
ReplyPHYSICS AS A SCIENCE
from Femosky110 on 06/12/2020 01:47 PMPhysics as a Science
We will start with a brief introduction to physics and its concepts. It is pertinent for us to note that physics like most pure science subjects uses symbols, formulae and equations in representing, defining or emphasizing scientific phenomena and challenges, especially in the teaching process. For example:
(g) = gravity = 9.8m/s 2
F = ma (formula for Newton's second law of motion)
All these we shall treat in subsequent lessons.
Physics is a natural science that involves the study of matter and its motion through space and time, along with related concepts such as energy and force. More broadly, it is the general analysis of nature, conducted in order to understand how the universe behaves.
Physics is a fundamental science. It is essential for all sciences and vital for modern technology. As noted earlier, Physics deals with the concepts of space, time and motion, conservation, fields, waves and quanta.
At secondary school level, physics is usually studied alongside Chemistry and Mathematics as these three subjects complement and supplement each other. A good understanding of all the three is very necessary for a career in Physics.
At advanced level, the more specialized areas of physics include
1. Astronomy,
2. Computational and Theoretical Physics,
3. Experimental physics,
4. Industrial and Condensed Matter Physics,
5. Medical and Biophysics,
6. Geophysics,
7. Solar Energy Physics among others.
Our main focus is physics for high school students so we will not deal with advance concepts in physics which is beyond the scope of this tutorials.
You can learn more about advance physics topic if you wish to pursue physics as a career or study further in high education.
Now let's take a look at the importance of physics and why we study physics.
physics
Importance of Physics to the Society
A statement adopted by IUPAP, March 1999 was
"Physics – the study of matter, energy and their interactions – is an international enterprise, which plays a key role in the future progress of humankind. The support of physics education and research in all countries is important because:"
1. Physics is an exciting intellectual adventure that inspires young people and expands the frontiers of our knowledge about Nature.
2. Physics generates fundamental knowledge needed for the future technological advances that will continue to drive the economic engines of the world.
3. Physics contributes to the technological infrastructure and provides trained personnel needed to take advantage of scientific advances and discoveries.
4. Physics is an important element in the education of chemists, engineers and computer scientists, as well as practitioners of the other physical and biomedical sciences.
5. Physics extends and enhances our understanding of other disciplines, such as the earth, agricultural, chemical, biological, and environmental sciences, plus astrophysics and cosmology – subjects of substantial importance to all peoples of the world.
6. Physics improves our quality of life by providing the basic understanding necessary for developing new instrumentation and techniques for medical applications, such as computer tomography, magnetic resonance imaging, positron emission tomography, ultrasonic imaging, and laser surgery.
In summary, physics is an essential part of the educational system and of any advanced society. We therefore urge all governments to seek advice from physicists and other scientists on matters of science policy, and to be supportive of the science of Physics.
This support can take many forms such as: National programs to improve physics teaching at all levels of the educational system.
Building and maintaining strong departments in universities and other academic institutions with opportunities to secure grants to support research, scholarships and fellowships for both undergraduate and graduate students studying physics, adequate fund for national laboratories and the formation of new ones as appropriate and funding and facilitating international activities and collaborations.
That was a statement issued by a group of Canadian physicists to their government in 1999, citing the need for more attention and support for physics and its study in our modern environment.
Careers in Physics
Once and again, the question any scholar of any idealism asks himself is, 'what jobs are there for physicists?'
The study of physics offers a broad range of job opportunities in
1. Meteorology
2. Telecommunication
3. Education
4. Medicine
5. Manufacturing
6. Space
7. Law and finance
8. Music and television
9. Environment
10. Architecture and Civil Engineering
11. Transport
12. Sports and Games
13. Energy and so forth.
Now I believe we have done enough theoretical approach to the introduction to physics. Let's now take a dip into some basic mathematical concepts in general physics.
Measurements
Measurement is the determination of the quantity of a body in terms of a certain chosen unit. The system of units acceptable internationally in most scientific measurements is called the International System of Units — SI for short.
There are two types of units namely:
Fundamental units
These are units upon which other units are derived from. There are three fundamental or basic units in physics. These are:
1. Metre – denoted (m) for Length.
2 kilogram – denoted (kg) for Mass.
3. Second – denoted (s) for Time.
These three fundamental units are very important to memories since they form the base upon which most other units depend.
The SI units of some fundamental quantities are summarized in the table below.
Quantity Unit abbreviation
Length meter m
Mass kilogram kg
Time second s
Temperature kelvin k
Electric current ampere A
Amount of substance mole mol
Derived units
As the name implies, Derived units are units derived from simple combination of two or more fundamental units. For example, the unit of volume ( m3 ) is obtained by multiplying three lengths — (m * m * m).
The below table shows some derived quantities and their units.
Quantity DerivationUnit Unit abbreviation
Area Length * breadth metre squared m2
Volume Length * breadth* height metre cubic m3
Density mass / Volume Kilogram per metre cubic kg/m3
Velocity Distance / time metre per second m/s
Acceleration Change in velocity / time metre per second squared m/s2
Force mass * acceleration Newton N
Energy force * distance Joules J
ORGANIC CHEMISTRY
from Femosky110 on 06/12/2020 01:31 PMOrganic Chemistry
Organic Chemistry study deals with the production of organic molecules and their reaction paths, interactions, and uses. Organic chemistry is a branch of chemistry that deals with the study of the structures, composition, and synthesis of carbon-containing compounds. For a good understanding of this type of chemistry, it is essential to make a note of the fact that that every organic molecule in addition to containing carbon also contains hydrogen. Although it is true that organic compounds can contain other elements, it is the bond between carbon and hydrogen that makes a compound organic.
Initially, Organic Chemistry was defined as the study of compounds formed by living organisms, but the definition was later widened to also encompass synthetically synthesized substances. Prior to the year 1828, every organic compound was obtained from living organisms.
Nomenclature of Alkanes
The table below illustrates the systematic names and arrangements of the first twenty straight chain alkanes. It is essential to get familiar with them as form the basis for naming countless other organic molecules all through your course of study.
Alkyl Groups
Alkanes can be depicted by the general formula CnH2n+2. An alkyl group is derived by removing one hydrogen from the alkane chain, and it can be depicted by the formula CnH2n+1. The removal of the one hydrogen gave rise to a stem change from -ane to –yl as exemplified in the examples below:
Similar concept can be applied to every straight chain alkane available in the table below:
Name Molecular Formula Condensed Structural Formula
Methane - CH4 - CH4
Ethane - C2H6 - CH3CH3
Propane - C3H8 - CH3CH2CH3
Butane - C4H10 - CH3(CH2)2CH3
Pentane - C5H12 - CH3(CH2)3CH3
Hexane - C6H14 - CH3(CH2)4CH3
Heptane - C7H16 - CH3(CH2)5CH3
Octane - C8H18 - CH3(CH2)6CH3
Nonane - C9H20 - CH3(CH2)7CH3
Decane - C10H22 - CH3(CH2)8CH3
Undecane - C11H24 - CH3(CH2)9CH3
Dodecane - C12H26 - CH3(CH2)10CH3
Tridecane - C13H28 - CH3(CH2)11CH3
Tetradecane - C14H30 - CH3(CH2)12CH3
Pentadecane - C15H32 - CH3(CH2)13CH3
Hexadecane - C16H34 - CH3(CH2)14CH3
Heptadecane - C17H36 - CH3(CH2)15CH3
Octadecane - C18H38 - CH3(CH2)16CH3
Nonadecane - C19H40 - CH3(CH2)17CH3
Eicosane - C20H42 - CH3(CH2)18CH3
Alkoxy Groups(Alkoxides)
Alkoxides are composed of an organic group bonded an oxygen atom that is negatively charged. Generally, they are written as RO-, where R stands for the organic substituent. Related to what obtainable in alkyl groups earlier discussed, the concept of naming alkoxides can be applied to every straight chain alkanes in the above table. and so on.
Three Basic Principles of Naming in organic chemistry
Select the longest, mainly substituted carbon chain containing a functional group.
A carbon that is bonded to a functional group must be the carbon atom in the chain with the lowest possible number. If there are no functional groups, next any substitute present should be given the smallest possible number.
After putting the 1st and second rules into consideration, ensure that you consider the alphabetical order and that your substitutes and/or functional groups are noted in alphabetical order.
Common Names of Branched Alkanes
A number of branched alkanes have common names that are still widely made use of today. These common names use prefixes like iso-, sec-, tert-, and neo-. The prefix iso-, stands for isomer. It is frequently given the name 2-methyl alkanes. What this means is that during naming, if there is methyl group situated on the second carbon of a carbon chain during naming, we could make use of the prefix iso-. The prefix will be placed in front of the alkane name which showcases the total number of carbons.
Examples are:
• Isopentane. This is the same as 2-methylbutane
• Isobutene This is the same as 2-methylpropane
To be able to allocate the prefixes sec-, which represents secondary, and tert-, which represents tertiary, it is essential that we first and foremost study how to classify carbon molecules. If a carbon is attached to only one other carbon, it is referred to as a primary carbon. If a carbon is attached to two other carbons, it is referred to a secondary carbon. A tertiary carbon is a carbon atom attached to three other carbons and finally, a quaternary carbon is a carbon that has carbon atom attached to it.
For instance:
• 4-sec-butylheptane (30g)
• 4-tert-butyl-5-isopropylhexane (30d);
Example of the usage of the prefix neo-
• neopentane
• neoheptane
Nomenclatures of Alkenes
Alkenes are a class of hydrocarbons that contain only carbon and hydrogen with a double bond. They are unsaturated compounds that contain at in the slightest one carbon-to-carbon double bond. Alkenes are also known as olefins.
Alkenes possesses carbon-carbon double bonds and are unsaturated hydrocarbons with the molecular formula is CnH2n. This is as well the same molecular formula that of cycloalkanes. Alkenes are named by leaving off the -ane ending of the parent alkane and replacing it with -ene.
Introduction of Alkene
The parent structure is the longest chain containing both carbon atoms of the double bond. The two carbon atoms of a double bond and the four atoms attached to them recline in a flat surface, with bond angles of approximately 120°. A double bond consists of one sigma bond created by overlap of sp2 hybrid orbitals and one pi bond fashioned by overlap of parallel 2 p orbitals.
The Basic Rules
For straight chain alkenes, it is equivalent basic rules as nomenclature of alkanes apart from the alteration with the suffix to "-ene."
i. Discover the Longest Carbon Chain that is bearing the Carbon to Carbon double bond. In a situation where we have two ties for longest Carbon chain, and both chains is bearing a Carbon to Carbon double bond, the most substituted chain should be discovered.
ii. The Carbon to Carbon double bond should be given the lowest possible number.
There is no need to number cycloalkenes due to the fact that the double bond is situated one position.
Alkene that possess equivalent molecular formula but which has the double bonds located in a different position is referred to as constitutional isomers.
The priority of Functional Groups during naming:
iii. After the two rules above, add substituents and their location to the alkene as prefixes. Do keep in mind to assign the lowest possible numbers. You must not forget to name them in alphabetical order when writing them.
iv. The next thing to do is to identify stereoisomers. When there are only two non hydrogen that are attached to the alkene, you should use cis and trans to name the molecule.
v. On the contrary when there there are 3 or 4 non-hydrogen dissimilar atoms attached to the alkene , you should use the E, Z system.
vi. Note that the hydroxyl group proceeds over the double bond. Consequently, alkenes possessing alcohol groups are referred to as alkenols. And the prefix for this group becomes -enol. And this means that in this group, the alcohol takes up the lowest priority against the alkene.
vii. Finally, note that alkene substituents are called alkenyl with the suffix -enyl.
Below is the systematic name and molecular formula of the first twenty straight chain alkenes.
Name - Molecular formula
Ethene - C2H4
Propene - C3H6
Butene - C4H8
Pentene - C5H10
Hexene - C6H12
Heptene - C7H14
Octene - C8H16
Nonene - C9H18
Decene - C10H20
Undecene - C11H22
Dodecene - C12H24
Tridecene - C13H26
Tetradecene - C14H28
Pentadecene - C15H30
Hexadecene - C16H32
Heptadecene - C17H34
Octadecene - C18H36
Nonadecene - C19H38
Eicosene - C20H40
Geometric Isomers
Double bonds can occur as geometric isomers and these isomers are selected by making use of the cis / trans designation or the modern E / Z designation.
cis Isomers
For Cis Isomers, the two largest groups are on the same side of the double bond.
trans Isomers
For trans Isomers, the two largest groups are on the opposite sides of the double bond.
Nomenclature of Alkynes
Alkynes are organic molecules that are made of the functional group of carbon-carbon triple bonds. Their empirical formula is CnH2n-2. They are unsaturated hydrocarbons. Similar to the alkenes they have the suffix –ene, alkynes use the ending –yne. This suffix is employed when there is only one alkyne in the molecule.
Below are the molecular formulas and names of the first ten carbon straight chain alkynes.
Name - Molecular Formula
Ethyne - C2H2
Propyne - C3H4
1-Butyne - C4H6
1-Pentyne - C5H8
1-Hexyne - C6H10
1-Heptyne - C7H12
1-Octyne - C8H14
1-Nonyne - C9H16
1-Decyne - C10H18
Ethyne is commonly known as acetylene. It is being made use of industrially.
Naming Alkynes
Just like the alkane and alkene the IUPAC rules are made use of while naming naming alkynes. Below are the rules to follow:
Rule no 1
Look for the longest carbon chain that contains the two carbon atoms of the triple bond.
Rule no 2
Assign number to the longest chain beginning from the end nearest to the triple bond. A 1-alkyne is known as a terminal alkyne and alkynes at any other place is referred to as internal alkynes.
For instance:
4-chloro-6-diiodo-7-methyl-2-nonyne
Rule 3
After assigning numbers to the longest chain with the lowest number, tag every one of the substituents at its equivalent carbon. In writing out the name of the molecule, organize the substituents in alphabetical order. If the substituents are more than one, they should be differentiated with the prefixes di, tri, and tetra for two, three, and four substituents correspondingly. These prefixes are not written in alphabetical order.
For instance:
1-triiodo-4-dimethyl-2-nonyne
Aromatic Hydrocarbons-Benzene
The adjective "aromatic" is employed by organic chemists in a relatively dissimilar way than what is usually applied.
Benzene
Properties/reactions of benzene
• Specific Substitution Reactions of Benzenes
• Electrophilic Aromatic Substitution of benzene
• Electrophilic Substitution of Disubstituted Benzene Rings
• Nucleophilic Reactions of Benzene Derivatives
• Reactions of merged Benzene Rings
• Reactions of Substituent Groups
• Substitution Reactions of Benzene Derivatives
Alchohols
Alcohols are among the most part significant molecules in organic chemistry. They can be prepared from a lot of dissimilar kinds of compounds and they can be transformed into various types of compounds. Alcohols are molecules possessing the hydroxy functional group (-OH) that is bonded to carbon atom of an alkyl or substituted alkyl. The hydroxy functional group powerfully adds to the physical properties of alcohols.
Nomenclature of Alcohols
In the IUPAC system of nomenclature, functional groups are usually nominated in one among two ways. The presence of the function may be showcased by a characteristic suffix and a location number. This is widespread for the carbon-carbon double and triple bonds which possess the respective suffixes ene and yne. Halogens, on the contrary do not possess a suffix and are named as substituents, for instance: (CH3)2C=CHCHClCH3 is 4-chloro-2-methyl-2-pentene.
Alcohols are normally named by the first procedure and are designated by an ol suffix, as in ethanol, CH3CH2OH
On longer chains, the position of the hydroxyl group decides the chain numbering. For instance
(CH3)2C=CHCH(OH)CH3 is 4-methyl-3-penten-2-ol.
For the mono-functional alcohols, this normal system is composed of naming the alkyl group followed by the word alcohol. Alcohols may as well be classified as primary, 1º, secondary, 2º & tertiary, 3º, in a similar manner to alkyl halides. This term is known as alkyl substitution of the carbon atom that is carrying the hydroxyl group. It is indicated with blue color in the diagram below.
Phenols
Compounds in which a hydroxyl group is bonded to an aromatic ring are known as phenols. The chemical behavior of phenols is dissimilar in some ways to that of alcohols. It is therefore sensible to discuss them as a similar but typically distinct group.
METALS AND COMPOUNDS
from Femosky110 on 06/12/2020 01:30 PMNon-Metals and Their Compounds
A nonmetal or non-metal in chemistry is a chemical element which does not have the characteristics of a metal. There is no exact and thorough definition of nonmetals. They exhibit more variability in their characteristics than metals.
Some physical properties of nonmetals are:
• They have the tendency to be extremely volatile. This means that they can easily turn into vapor.
• Their elasticity is very low
• They are excellent insulators of heat and electricity
• They mainly exist as monatomic gases, with some of them possessing more considerable although, still open-packed diatomic or polyatomic forms, contrary to metals which are almost all solid and tightly-packed.
• When a non-metal is a solid, it is characteristically possesses a sub metallic property, it has a dull appearance and is brittle, contrary to metals, which are lustrous, ductile or malleable.
• Non-metals normally have lower densities than metals.
• They are poor conductors of heat and electricity when compared to metals.
• They have significantly lower melting points and boiling points than those of metals apart from carbon
Some chemical properties of non-metals are:
• They have lofty ionization energy and electro negativity values
• They accept or share electrons when reacted with other elements or compounds.
The elements that are normally classified as nonmetals are 17 in number. They are mostly gases like hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon, krypton, xenon and radon. One of them is liquid Bromine is the liquid non-metal.
Some of them are solids. Solid no-metals are carbon, phosphorus, sulfur, selenium, and iodine.
As you move across the period of a typical periodic table, nonmetals adopt structures that have increasingly fewer close neighbors. Polyatomic nonmetals have arrangements or shapes with either 3 close neighbors. This is exemplified in carbon when nit is in its standard stated in graphite. They can as well possess 2 close neighbors as you would obtain in sulphur. On the centrally, diatomic non-metals like hydrogen, possess only one close neighbor, and the monatomic noble gases, like helium do not have any close neighbor.
The systematic decline in the number of close neighbors is connected with a decrease in metallic character and a boost in nonmetallic character. The difference that exists among the three types of nonmetals, with regards to declining metallic properties is not unlimited. Boundary overlaps arise as remote elements in every category illustrate or start to exhibit less-distinct, hybrid related or a distinctive property.
Even though the numbers of elements that metals five times exceed the numbers of elements that are nonmetals, two of the nonmetals—hydrogen and helium—constitute above 99 per cent of the visible Universe, and another one, oxygen, constitute almost half of the Earth's crust, oceans and atmosphere. Living organisms are as well made entirely of nonmetals. Nonmetals constitute countless more compounds than metals.
Chemically, the nonmetals have comparatively high ionization energy and high electro negativity.
They usually exist as anions or oxyanions in aqueous solution.
They generally form ionic or interstitial compounds when reacted with metals, as opposed to metals which form alloys. Non metal have acidic oxides while the regular oxides of the metals are basic in nature.
Non- metallic elements
The elements that are usually categorized as nonmetals consist of one element in group 1 and group 14: hydrogen (H) and carbon (C); 2 elements in group 15 pnictogens ie nitrogen (N) and phosphorus (P); 3 elements in group 16 (the chalcogens): oxygen (O), sulfur (S) and selenium (Se); most elements in group 17 known as the halogens: fluorine (F), chlorine (Cl), bromine (Br) and iodine (I); and all elements in group 18 known as the noble gases, with the likely exclusion of ununoctium (Uuo).
The difference between nonmetals and metals is not very clear. The outcome is that some intermediate elements which are deficient of a predominance of either nonmetallic or metallic properties are classified as metalloids; and some elements under the category of nonmetals are as an alternative occasionally classified as metalloids, or vice versa. For instance, selenium (Se), a nonmetal, is occasionally classified alternatively as a metalloid, mainly in environmental chemistry; and astatine (At), which is a metalloid and a halogen, is occasionally alternatively classified as a nonmetal.
Nonmetals have structures in which every atom normally forms (8 − N) bonds with (8 − N) closest neighbors, where N stands for the number of valence electrons. Every one of the atom is by this means capable of filling its valence shell and attaining a stable noble gas configuration. The exclusions to the (8 − N) rule take place with hydrogen which merely requires one bond to achieve its octet configuration, carbon, nitrogen and oxygen. Atoms of the last three elements are adequately minute that they are capable of forming substitute and more stable bonding structures, with smaller amount of close neighbors.
Thus, carbon is capable of forming its layered graphite structure, and nitrogen and oxygen are capable of forming diatomic molecules with triple and double bonds, in that order. The bigger size of the rest non-noble nonmetals deteriorates their ability to form multiple bonds and they on the contrary form two or more single bonds to two or more dissimilar atoms. Sulfur, for instance, forms an eight-membered molecule in which the atoms are prearranged in a circle, with ever one of the atoms forming two single bonds to dissimilar atoms.
From left to right across the periodic table, as metallic character declines, nonmetals consequently assume structures that illustrate a steady decline in the numbers of closest neighbors—three or two for the polyatomic nonmetals, all the way through one for the diatomic nonmetals, to zero for the monatomic noble gases.
A comparable prototype takes place usually, at the level of the whole periodic table, in comparing metals and nonmetals. There is a switch from metallic bonding among the metals on the left hand side of the table through to covalent or Van der Waals (electrostatic) bonding among the nonmetals on the right side of the periodic table. Metallic bonding have the tendency to engage close-packed central symmetric structures with a high number of close neighbors. Other metals and metalloids, between the true metals and the nonmetals, have the tendency to posses more complex structures with an intermediary number of close neighbors.
Nonmetallic bonding, at the right side of the periodic table, exhibits open-packed directional or muddled up structures with fewer or zero close neighbors. As noted, this fixed reduction in the number of close neighbors, as metallic character declines and nonmetallic character augments, is reflected in the midst of the nonmetals, which have structures that gradually vary from polyatomic, to diatomic, to monatomic.
This happens with key categories of metals, metalloids and nonmetals, there are a little variation and overlapping of properties within and across every category of nonmetal. Amongst the polyatomic nonmetals, carbon, phosphorus and selenium which are at the margin of the metalloids start to show some metallic character.
Polyatomic nonmetals
Four nonmetals are well-known to form polyatomic bonding in their average states, in either distinct or extensive molecular forms: carbon (C, in the form of graphite sheets; phosphorus in the form of P4 molecules; sulfur in the form of S8 molecules; and selenium Se, in the form of helical chains. Polyatomic nonmetals exhibits more metallic character than the adjoining diatomic nonmetals; every one of them are solid, mainly semi-lustrous semiconductors with electro negativity values that are midway to more or less high. Sulfur is the least metallic of all the polyatomic nonmetals due to its properties of dull appearance, brittle comportment, and stumpy conductivity. This is a characteristic found in all sulfur allotropes. It nonetheless exhibits a number of metallic characters, either essentially or in its compounds with other nonmetals.
The differences between the polyatomic nonmetals and the diatomic nonmetals are: They possess higher organization numbers, elevated melting points, and high boiling points. They have a wider liquid ranges and lower room temperature instability. In general, they exhibits a marked tendency to occur in allotropic forms, and a stronger tendency to catenate; and have a weaker propensity to form hydrogen bonds.
Diatomic nonmetals
There are7 nonmetals that are diatomic molecules in their standard states. These are hydrogen (H2); nitrogen (N2); oxygen (O2); fluorine (F2); chlorine (Cl2); bromine (Br2); and iodine (I2). They are usually greatly insulating, exceedingly electronegative, non-reflective gases, but bromine which is a liquid, and iodine which is a solid, are both unstable at room temperature.
The diatomic nonmetals can be differentiated from the polyatomic nonmetals because they have lower coordination numbers, lesser melting points and lesser boiling points; and possessing narrower liquid ranges and larger room temperature explosive nature.
Noble gases
Six nonmetals exist in nature as monatomic noble gases: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and the radioactive radon (Rn). They are composed of chemical elements with extremely similar properties. In their standard states, they are all colorless, odourless, nonflammable gases with typically extremely low chemical reactivity.
Elemental gases
Hydrogen, nitrogen, oxygen, fluorine, chlorine, in addition to the noble gases is jointly referred to as the elemental gases. They are differentiated by having the lowest densities, they have lowest melting and boiling points, strongest insulating properties, and highest electronegativity plus ionization energy values in the periodic table.
NON METALS
from Femosky110 on 06/12/2020 01:28 PMMetals and their compounds
The greater part of elements in the Periodic Table is metals. Metals vary from the extremely reactive alkali metals like sodium to inert metals like gold.
Metals have common physical properties but variable chemical properties.
The physical properties of metals are:
• Metals are glossy, solid and good conductors of heat and electricity.
• Metals have high density.
• They are malleable and ductile, deforming under strain without cutting.
• Metals are shiny and lustrous.
Sheets of metal below a few micrometers in breadth have opaque appearance apart from Gold leaf which gives off green light.
Even though majority of metals have lofty densities than nearly all nonmetals, they have broad variation in their densities, with Lithium being the slightest dense solid element and osmium the densest.
The alkali and alkaline earth metals in groups I A and II A are known as the light metals for the reason that they have small density, less hard and low melting points. The lofty density of the majority of metals is due to the firmly packed crystal lattice of the metallic structure. The strength of metallic bonds for dissimilar metals reaches the utmost around the center of the transition metal series, since those elements have huge amounts of delocalized electrons in tight binding form of metallic bonds. Nevertheless, other factors like atomic radius, nuclear charge, amount of bonds orbital's' overlap of orbital energies and crystal form are also involved.
Chemical properties of metals
• Metals have the tendency to form cations through loss of electron.
• They react with oxygen in the air to form oxides. This explains why metals like iron rust when they are exposed over a long period of time and why potassium instantly burns in the presence of oxygen in the atmospheric air.
• For Example: Sodium, calcium and aluminum reacts with air to for their oxides respectively as exemplified in the equations below:
4 Na + O2 → 2 Na2O (sodium oxide)
2 Ca + O2 → 2 CaO (calcium oxide)
4 Al + 3 O2 → 2 Al2O3 (aluminum oxide)
The transition metals like iron, copper, zinc, and nickel are less reactive. They don't easily react with oxygen in the air due to the fact that they form passive layer of oxide that shields the core. Other metals like palladium, platinum and gold, are completely not reactive with air. Some metals form a barricade layer of oxide on their surface which could hardly be pierced by extra molecule of oxygen. In so doing, they maintain their lustrous appearance and continue to be good conductors of electricity for ages. Examples are aluminum, magnesium, various steels, and titanium
Metallic oxides are characteristically basic in nature contrary to the oxides of non-metals which are normally acidic in nature. Obvious exceptions are mainly oxides of metal with especially high oxidation states like that of CrO3, Mn2O7, and OsO4, which have severely acidic reactions.
Prevention of rusting or corrosion of metals
Metals can be protected to prevent them rusting when exposed to atmospheric air through the following procedures Painting, anodizing or plating of metals. Although, a metal that is more reactive in the electrochemical series must be used for coating particularly when chipping of the coating is anticipated. Water and the two metals form an electrochemical cell. If the metal used for coating is less reactive than the coated metal, the coating will in fact encourage corrosion.
Corrosion of metals
Metals have many useful physical properties
• The strength of metals is useful in girders
• The reflective power of metal is useful in headlamps
• The electrical conductivity of metals is useful in making electrical cables
•Metals are stable to heat and this characteristics is useful in engines
Metals higher up in the series will displace those further down the series
Zn (metal) + Cu2+ + → Cu (metal) + Zn2+
This type of reaction is known as redox reactions.
Metallic Structure and bonding:
The atoms of metals are packed closely to adjoining atoms in one of two common arrangements. The first arrangement is known as body-centered cubic. In this arrangement, each atom is positioned at the center of eight others. The second arrangement is referred to as face-centered cubic. In this second arrangement, every atom is placed at the middle of the other six. This leads to the formation of a crystal. A few metals have variable shape depending on the temperature condition.
Metallic atoms easily give out their valence electrons, leading to the formation of free flowing cloud of electrons within their solid arrangement. This is why metals have the ability to readily conduct heat and electricity. As there are free movements of these electrons, the metallic structure are kept intact by the electrostatic interactions between every atom and the electron cloud. This is what is normally known as metallic bond.
Electrical and thermal conductivities of metals
Electrical
The electrical and thermal conductivities of metals started off from the reality that their external electrons are delocalized. This circumstance can be seen through the atomic structure of a metal as a compilation of atoms implanted in a sea of extremely mobile electrons. The electrical conductivity, together with the electrons' contribution to the heat power and heat conductivity of metals can be considered and estimated through the free electron model, which does not take into consideration the comprehensive arrangement of the ion lattice.
Mechanical Properties of metal
Mechanical properties of metals are:
• Ductility- This is their aptitude for plastic deformation.
Reversible elastic deformation in metals can be explained through Hooke's Law for reinstating forces, where the stress is directly proportional to the strain. Forces applied in excess of the elastic limit or heat may lead to irreversible deformation of the object. This phenomenon is known as plastic deformation or plasticity. This irreversible change in atomic arrangement may occur as a result of:
• The action of an applied force which can be tensile (pulling) force, compressive (pushing) force, cut off, twisting or torsion (twisting) forces.
• An alteration in temperature (heat) which may alter the movement of the structural defects.
Alloys
An alloy is a mixture of two or more elements in which the major component is a metal. The majority of pure metals are either too soft, brittle or chemically reactive for realistic use. Combination of various ratios of metals as alloys adjusts the properties of pure metals to manufacture enviable characteristics. The major reason for forming alloys is to make the metals less brittle, harder, anti corrosive, or enclose a more attractive color and luster.
Among the current available alloys, the alloys of iron, steel, stainless steel, cast iron, tool steel and alloy steel constitute the principal percentage both by magnitude and commercial value. Iron that is alloyed with a variety of proportions of carbon yields low, mid and high carbon steels, with escalating carbon levels lowering ductility and toughness. The adding together of silicon will give rise to cast irons, while addition of chromium, nickel and molybdenum to carbon steels in a quantity over 10% will give rise to stainless steels.
Other noteworthy metallic alloys are alloys of aluminum, titanium, copper and magnesium. Copper alloys have been discovered early in history.
Bronze was what gave the Bronze Age its name. It is used for many things today especially in electrical wiring. The alloys of additional three metals have been developed quite lately; for the fact of their chemical reactivity they need electrolytic extraction processes. The alloys of aluminum, titanium and magnesium are prized for their lofty strength/weight ratios; magnesium can also offer electromagnetic shielding. These materials are perfect for situations where elevated strength/weight ratio is more crucial than the cost of the material like in aerospace and a number of automotive applications.
Alloys are especially designed for extremely challenging applications, like jet engines and may include more than ten elements.
Base metal
The term base metal is used in Chemistry to refer to a metal that oxidizes or corrodes rather simply, and reacts variably with dilute hydrochloric acid (HCl) to form hydrogen. Examples of base metals are iron, nickel, lead and zinc. Copper is also well thought-out to be among base metals as it oxidizes rather readily, even though it does not act in response with HCl. It is generally used contrary to noble metal.
A base metal was a widespread and low-priced metal, contrary to precious metals, like gold and silver. The purpose of work of the alchemists was the transformation of base metals into precious metals.
Ferrous metal
Ferrous and non-ferrous metals
Ferrous metals are metals that contain iron. The expression "ferrous" is derived from a Latin word. Ferrous means "containing iron". The iron may be pure iron like wrought iron, or an alloy like steel. Ferrous metals are frequently magnetic, but not completely.
Noble metal
Noble metals are metals that doesn't corrode or oxidize as opposed to most base metals. They are inclined to be valuable metals, frequently due to apparent rarity for instance, gold, platinum, silver and rhodium.
The Reactivity Series of metals
The activity series of metals is an empirical instrument used to foresee products in displacement reactions and reactivity of metals with (H20) water and acids in replacement reactions and ore extraction. It can be employed to foretell the products in related reactions connecting dissimilar metal.
The activity series is a chart of metals written in descending order of their relative reactivity. The metals on top of the series are more reactive than the metals on the foot. For instance, both magnesium and zinc can react with hydrogen ions to displace H2 from a solution by the reactions below:
Mg(s) + 2 H+(aq) → H2 (g) + Mg2+ (aq)
Zn(s) + 2 H+(aq) → H2(g) + Zn2+(aq)
The two metals react with the hydrogen ions, but magnesium metal can as well displace zinc ions in solution by the reaction below:
Mg(s) + Zn2+ → Zn(s) + Mg2+
This signifies that magnesium is additionally reactive than zinc and that the two metals are more reactive than hydrogen.
By comparing the reactions of metals in oxygen, water and acid, metal oxides and solutions of metal salts, we can organize metals into a list of reactivity known as the Reactivity Series. The more reactive a metal is the more able it is to form a compound. Again, the more reactive a metal, the more stable its compound.
Furthermore, the more reactive a metal, the more difficult it is to extract from its compounds.
Copper, silver and gold exist as elements in the earth because they are un reactive in nature. They are easy to extract.
Reactive metals are additionally difficult to extract. They are frequently discovered as compounds or ores.
A method of extraction known as Electrolysis is used to eliminate the element from the rest of the compound.
Extraction of Metals
Metals are habitually extracted from the Earth through the process of mining, leading to ores that are reasonably rich sources of the essential elements.
Immediately the ore is mined, the metals need to be extracted, usually through the use of a chemical or through electrolysis.
The extraction method to be used depends on the metal and their impurity.
When a metallic ore is present in an ionic compound of the metal and a non-metal, the ore have got to be smelted. This means heating it up with a reducing agent to extract the pure metal.
The majority of ordinary metals, like iron, are smelted with carbon as a reducing agent. Some metals, like aluminum and sodium, have no reducing agent that is commercially sensible. Because of this, they are extracted through the process of electrolysis. Sulfide ores are not reduced straight to the metal but are burnt in air to convert them to oxides.
CHEMISTRY AND ENVIRONMENT
from Femosky110 on 06/12/2020 01:27 PMCHEMISTRY, INDUSTRY AND THE ENVIRONMENT
Is chemistry and industry any help to our environment or is it an obstacle?
Environmental problems and concerns like climate change, water pollution and renewable energy constantly constitute the headlines of news in radio, television, newspapers, magazines and even online, everywhere. In fact the issue has come to stay as an unavoidable part of our day to day life. A lot of people consider chemistry and the chemical industry as injurious to the environment. Nevertheless, numerous innovative progresses and scientific researches in the area of chemistry are assisting us to build up additional environment friendly materials and applications, whilst safeguarding the worth and the standard of living we look forward to.
Down the years, the chemistry and chemical industry and the public at large discovered the dangerous effects of a few chemical practices and how essential it is to ensure the safety of our environment. Previously the awareness regarding the harmful effect of our advanced way of life is very minimal. What was more perceived then is the positive impact of technology and advancement of manufacturing helpful innovative materials and products.
Research conducted in the field of biological sciences and chemistry has exposed that industrial procedures in chemistry and petrochemistry could contribute in discovering solutions to environmental problems like the climate change, waste management, recycling, and energy efficiency and so on. If there was nothing like "chemistry", it would have been very difficult to fully comprehend these environmental problems let alone providing solutions to getting the issues resolved more ways.
Nowadays, chemists and petrochemists are conducting research into discovering fresh methods that are more sustainable and environmentally friendly and at the same time preserving the advancement of our economy and our industry. Examples incorporate:
• Biofuels: Biofuels is the transportation fuel resulting from biomass. There are many product of biomass like sugar cane, rape seed, corn, straw, wood, animal and agriculture remains and waste product can be changed into fuels for transport;
• Bioplastics: This is the process through which plastic materials are produced with the help of natural sources like plants that are biodegradable and which would constitute no environmental hazard;
• Insulation: The study of chemistry had made possible improved insulating materials to facilitate higher energy-efficient homes and buildings;
• Less heavy plastic composites that have also been made possible through technological advancement help to minimize cars and airplanes propensity to consume fuel;
• Fuel cells: Fuel cells are another alternative to fossil fuels. When it is utilized as fuel in cars or motorbikes, the hydrogen fuel cells manufactures water vapour as an alternative for exhaust gases;
• New lighting technologies: Technology like Organic Light Emitting Diodes - OLEDS which produce more light with less electricity;
• Both Wind turbines and solar paneling: depend on materials manufactured by the chemical industry. The metal blades of wind turbines have to a great extent been replaced by blades that are manufactured with a fibre glass-reinforced polyester to withstand a harsh weather condition.
The Society has the tendency of considering every artificial chemical as dreadful and all that is natural as good. The mere fact that something is natural does not automatically mean that it is fine for the health or the environment or hazardous if it's an artificially made chemical. The burning of wood for an example appears to be natural but the smoke that is given out when a wood is burnt can be detrimental the health and environment just like every other processes of burning.
THE EXTRACTION OF METALS
We will only talk about the many factors that determine the choice of method for extracting metals from their ores, like reduction by carbon, reduction by a reactive metal such as sodium or magnesium, and reduction by electrolysis.
What are "ores"?
An ore is any natural source of a metal that you can inexpensively extract the metal from.
Aluminum, for instance is the most naturally occurring metal on earth. It is found in different kinds of minerals. Nevertheless, it is not cost effective to extract aluminum from the majority of these minerals. As an alternative, the common ore of aluminum is bauxite - which is composed of 50 - 70% of aluminum oxide.
Copper is less found in nature but can luckily be extracted from high-grade ores ie ores with a great percentage of copper in certain places. The fact that copper is a valuable metal, necessitates that it is extracted as well from low-grade ores.
Ores are mainly
1. oxides - for instance:
bauxite Al2O3
haematite Fe2O3
rutile TiO2
2. sulphides - for instance:
pyrite FeS2
chalcopyrite CuFeS2
Concentrating the ore
Concentrating the ore or making the ore concentrated merely means to get rid of as much of the unnecessary rocky material as possible from the ore before it is transformed into the metal.
Occasionally this is carried out chemically. For instance, pure aluminum oxide is extracted from bauxite by a procedure that involves a reaction with sodium hydroxide solution. A number of copper ores can be transformed into copper (II) sulphate solution by allowing the crushed ore in contact with dilute sulphuric acid to stand for a long time. Copper can afterward be extracted from the copper (II) sulphate solution.
But, in a lot of instances the metal compound can be separated from not needed rocky material by physical means. An example of this is shown through froth flotation.
Reduction of the metal compound to the metal
Why the process is a reduction process.
When you are starting compound is an oxide of a metal, the ore is normally being reduced due to the removal of oxygen from it.
On the other hand, when your starting material is a sulphide ore, a reduction by the removal of oxygen doesn't help here. What is more feasible in this situation is a reduction by electron addition.
You can consider these ores as possessing positive metal ions. To convert them to the metal, you would require addition of electrons by reduction.
Selecting a method of reduction
There are many economic factors you need to consider when deciding a method of reduction to use for a particular type of ore. Some of the factors are:
• The cost of the reducing agent;
• The cost of energy;
• The extent of purity you are requiring in the metal.
There might be other environmental factors to also consider.
Reduction by Carbon
Carbon (as coke or charcoal) is very cheap. It acts as both the reducing agent and the fuel that makes available the heat for the reduction process.
However, in some cases for instance with aluminum the temperature necessary to reduce carbon is very high and is not economically feasible. In this situation, another method of reduction is employed.
Carbon might as well be left in the metal as a contamination. Sometimes this can be detached after that for instance in the extraction of iron; sometimes it can't as an example in the process of producing titanium. As a result another method is employed for such situations.
Reduction with the help of a more reactive metal
Titanium is extracted by reducing titanium (IV) chloride with a more reactive metal like sodium or magnesium. This is the only method of obtaining a high purity metal from its ore.
The more reactive metal sodium easily gives out electrons when forming its ions. As illustrated in the equation below:
These electrons are employed in the reduction of titanium(IV) chloride. The problem with this method of extraction is that is very costly. The more reactive metal is very difficult and expensive to extract. It would necessitate the use of an expensive reducing agent to reduce a metal like titanium for an example.
Reduction by electrolysis
Reduction by electrolysis is a popular method of reducing a more reacting metal from their ore for instance Aluminum and all the metals that above it in the homologous series. It is a method of extracting copper and as well for the purification of copper. During the process of the electrolysis, electrons are being deposited directly to the metal ions at the negative electrode or cathode leading to the reduction of the metal ion into a neutal metal atom.
The disadvantage of this is the cost of the electricity as in the case of aluminum but the good thing about it is the possibility of obtaining a very pure metal.
An alloy
An alloy is a mixture or solid solution of two or more metal. An alloy possesses one or more of three of the following
1. solid solution of the elements (a single phase)
2.A mixture of metallic phases (two or more solutions)
3. An intermetallic compound with no separate boundary between the phases.
Solid solution alloys give one solid phase microstructure, whereas partial solutions displays two or more phases that might or might not be homogeneous in supply, consequent on the thermal treatment history of the substance. An inter-metallic compound has another alloy or pure metal implanted inside another pure metal.
Alloys are employed in certain applications, where their properties are better than those of the pure constituent elements for a particular application. Examples of alloys are solder:
• brass,
• pewter,
• phosphor bronze
• steel
• and an amalgam.
Steel for an example is an alloy of iron with carbon and, normally, minute amounts of some other elements, each of which gives a number of exclusive characteristic to steel.
Stainless steel alloys are a combination of iron, chromium and nickel commonly customized by the presence of other elements. This family of alloys is for the most part dead set against corrosion, in disparity with the rusting observable fact that destroys normal steel;
• Beryllium-copper alloys has more strength and higher electrical conductivity power than the rest alloys of copper;
• gallium arsenide is a an extremely conducting alloy used in laser-beam technology;
• super alloys of nickel and cobalt are made use of in aircraft engines for the reason that they are corrosion free and heat-resistance;
• aluminum with minute quantities of silicon, iron, copper, manganese, magnesium and zinc forms an alloy specially made for the production of beverage cans;
Land, Air And Water Pollution
What is pollution?
Pollution is the addition of a contaminant into the environment. It is caused mainly by human actions, but can as well a result of natural disasters.
Pollution is harmful to the Earth's environment and things that live on it in various ways.
The three main types of pollution are:
Land Pollution
Land pollution is contamination of the Earth's natural land surface by industrial, commercial, domestic and agricultural practices.
Sources of land pollution
Some of the key sources of land pollution are:
• Chemical and nuclear plants
• Industries and factories
• Oil refineries
• Human sewage
• Oil and antifreeze leakage from automobiles
• Mining
• Littering around
• Overcrowding of landfills
• Deforestation
• The debris from construction
Air Pollution
Air pollution is the building up of harmful materials into the atmosphere that have the tendency of endangering human life and other living things
Sources of air pollution
Some air pollution are:
• Emissions by Automobile
• The smoke of Tobacco
• Burning of coal
• Acidic rain
• Noise pollution from cars and production industries, Power plants, building constructions, outsized ships, fumes from paints, sprays of Aerosol, Wildfires and Nuclear weapons
Water Pollution
Water pollution is caused by the introduction of chemical, biological and physical materials into large water bodies which reduces the quality of life that lives in the water and lives that makes use of the water for survival.
Sources of water pollution:
Some key sources of water pollution are:
• Factories and refineries
• Waste treatment plants and facilities
• Mining
• Pesticides, herbicides and fertilizers that are non-biodegradable
• Human waste
• Oil spills
• Faulty septic systems
• Soap from our washing
• Oil and antifreeze leakage from cars
• Domestic chemicals
• Animal waste
CARBON COMPOUND
from Femosky110 on 06/12/2020 01:25 PMCHEMISTRY OF CARBON COMPOUNDS
The chemistry of carbon is subjugated by three features.
1. Carbon forms extraordinarily strong carbon-carbon (C-C) single bonds, carbon-carbon (C=C) double bonds, and carbon-carbon triple bonds.
2. The electronegativity of carbon (EN) = 2.55 is very small to permit carbon to form C4- ions with the largest part of metals and very large for carbon to form C4+ ions when it reacts with nonmetals. Carbon as a result forms covalent bonds with countless other elements.
3. Carbon forms strong double and triple bonds with many other nonmetals, which includes N, O, P, and S.
Chemistry of Carbon
Organic chemistry involves structures and reactions of mostly carbon and hydrogen. Inorganic chemistry involves every other pure element apart from carbon. The inorganic chemistry of carbon is as well known as inorganic carbon chemistry. It is the chemistry of carbon that does not fall into the category of the organic chemistry sector.
Inorganic Chemistry of Carbon
Inorganic carbon chemistry is carbon that is extracted from ores and minerals, in opposition to organic carbon originate in nature through plants and living things. A few instances of inorganic carbon are carbon oxides like carbon monoxide and carbon dioxide; polyatomic ions, cyanide, cyanate, thiocyanate, carbonate and carbide in carbon. Carbon is an element that is exceptional in itself. Carbon forms strong single, double and triple bonds and for that reason it normally requires extra energy to break these bonds than when carbon is bonded to another element.
For carbon monoxide the reaction is denoted with the equation below:
2C(s) + O2 → 2CO(g) Enthalpy of -110.52 kJ/mol CO
C(s) + O2 → CO2(g) Enthalpy of -393.51 kJ/mol CO2
CO and CO2 are together gases. CO has no smell or taste and can be deadly to living organisms if in contact at even extremely small amounts of one thousandth of a gram. This is due to the fact that CO will react with the hemoglobin that carries oxygen in the blood. CO2 is not deadly except the living organisms are exposed to bigger amounts of it, in relation to 15%. CO2 manipulates the atmosphere and also the temperature via the effect of the greenhouse gas. While heat is caged in the atmosphere by CO2 gases, the temperature of the Earth's increases. The main supply for CO2 in our atmosphere, in the midst of scores of them is volcanoes.
Allotropes of carbon
Examples of the inorganic chemistry of carbon allotropes are diamond, graphite and fullerenes.
• Inorganic carbon may exist in the form of diamond. Diamond is crystal clear, isotropic crystal. It is the hardest naturally existing substance on earth. Diamond has four valence electrons, and when each one of the electrons forms bonds with another carbon it forms a sp3-hybridized atom. The boiling point of diamond is 4827°C.
• Unlike diamond, graphite is opaque, spongy, dull and hexagonal. Graphite can act as a conductor (electrodes) or merely as pencils. Graphite is made up of planes of sp2 hybridized carbon atoms in which each carbon is linked to the other three carbons.
• Fullerenes are carbon cages that are denoted with the formula C2n where n > 13. The most available fullerene is the sperical C60. Fullerene might have atoms or molecules within the cage (endohedral fullerenes) or covalently linked outside (exhoedral or adduct fullerenes).
Formulas of Inorganic and Organic Compounds
A chemical formula is an arrangement utilized to convey the structure of atoms. The formula shows which elements and the number of every element that are available in a compound. Formulas are written with the help of the elemental symbol of every atom and a subscript to signify the number of elements.
The most widespread elements available in organic compounds are carbon, hydrogen, oxygen, and nitrogen. With carbon and hydrogen available, other elements, like phosphorous, sulfur, silicon, and the halogens, might be present in organic compounds. Compounds that do not follow this regulation are called inorganic compounds.
Chemical Formulas
Chemical formulas can be further sub divided into empirical formula, molecular formula, and structural formula. Structural formular can be written complete or in its condensed form. Chemical symbols of elements in the chemical formula stand for the elements available and subscript numbers correspond to mole proportions of the scheduled elements.
H H | | H-C-C-O-H | | H H
Structural formular of CH3CH3OH
C6H12
A structural formula showcases the way the atoms in a molecule or ion are bonded. For instance, ethanol can be represented by CH3CH2OH. This is a condensed or simple way to illustrate the complicated structure above.
Molecular Geometry and Structural Formula
The knowledge of the way atoms in molecules are arranged and the way they are bonded together is extremely essential in providing the molecule with an identity. Isomers are compounds with the same number of atoms, and thus the same molecular formula, but which have entirely different physical and chemical properties due to the differences in their structural formula.
Molecular Formula
The molecular formula is derived from the authentic makeup of the compound. Even though the molecular formula can occasionally be same with the empirical formula, molecular compounds have the tendency to be more useful. Nevertheless, they do not illustrate the way the atoms are put together. Molecular compounds are as well deceptive when handling with isomers, which possess identical number and types of atoms.
Example-The Molecular Formula of Ethanol is C2H6O.
Empirical Formula
The empirical formula formular of a compound shows the simplest formular of the compound. Empirical formulas exhibit the number of atoms of every element in a compound in the most simplified form with the help of integers or whole numbers. Empirical formulas have the tendency to show a little consigning a compound as it is not possible to know the structure, shape, or properties of a compound without the knowledge of its molecular formula. The worth or value of the empirical formula is less due to the fact that a lot of chemical compounds can posses the same empirical formula.
Example-To find the empirical formula of C8H16O2.
To get the answer, you divide each and every one of the subscript by 2 to get the smallest ratio of whole numbers.
Structural Formula
A structural formula showcases the atoms in a molecule in the order they are bonded. It also depicts the way the atoms are bonded to one another just like in single, double, and triple covalent bond. Covalent bonds are illustrated with the help of lines. The numbers of dashes illustrates if the bond is a single, double, or triple covalent bond. Structural formulas are of a great help due to the fact that they give details about the properties and structure of the compound which empirical and molecular formulas cannot constantly showcase.
Condensed Structural Formula
Condensed structural formulas illustrate the order of atoms as you would obtain in a structural formula other than they are written just in a single line to economize space and make it additionally suitable and quicker to write. Condensed structural formulas are as well useful when illustrating that a group of atoms is associated with one atom in a compound. When this occurs, parenthesis is utilized just about the group of atoms to illustrate that they are together.
Example of Condensed Structural Formula-The condensed structural formula of Ethanol: CH3CH2OH (Molecular Formula for Ethanol C2H6O).
A homologous series
The homologous series of compounds with comparable general formula regularly vary by one parameter like the length of a carbon chain. Examples of a homologous series are the straight-chained alkanes (paraffins), the akenes with double bonds and alkynes with triple bonds and some of their derivatives like the primary alcohols, aldehydes, and mono carboxylic acids. Another homologous series is the single-ring un-branched cycloalkanes.
Elemental Forms of Carbon: Graphite, Diamond, Coke, and Carbon Black
Carbon exists as a diversity of allotropes. The various allotropes of carbon are two crystalline forms- diamond and graphite and a lot of amorphous or non crystalline forms, like charcoal, coke, and carbon black.
The properties of diamond are a reasonable significance of its structure. In a diamond Carbon, with its four valence electrons, forms covalent bonds to four adjoining carbon atoms prearranged near the corners of a tetrahedron, every one of the sp3-hybridized atoms are then bonded to 4 other carbon atoms, which in turn form bonds to 4 other carbon atoms, and the bond continues in like manner. Owing to this, an ideal diamond can be considered of as one giant molecule. The might of each individual C-C bonds and their organization in space results to the abnormal properties of diamond.
In a number of ways, the properties of graphite are similar to those of diamond. Both diamond and graphite boil at 4827oC, for instance. But graphite is as well extremely dissimilar to diamond. Diamond with the density of (3.514 g/cm3) is denser than graphite with the density of 2.26 g/cm3. While diamond is the hardest known substance, graphite is one of the softest substances available. Diamond is an brilliant insulator, with minimal or zero inclination to allow the passage of electric current through it. Graphite is an excellent conductor of electricity and as a result, electrodes made with graphite are made use of in the construction of electrical cells.
The physical properties of graphite can be implicit from the structure of the solid.
Graphite is composed of extended planes of sp2-hybridized carbon atoms with every one of the carbon atom firmly bound to three other carbon atoms.
The reason for the high melting point it possesses is due to the strong bonds linking carbon atoms within every plane. The distance flanked between these planes of atoms, nevertheless, is very much bigger than the distance between the atoms inside the planes. Since the bonds between planes are weak, it is very simple to distort the solid by permitting one plane of atoms to shift in relation to the other. Owing to this, graphite is very soft and is being used in pencil and as a form of lubricant in motor oil.
"Lead" pencils do not, by the way, contain lead which is very good due to the fact that a lot of people chew up pencils and lead compounds are poisonous. Lead pencils are made with graphite or "black lead as it was formally called with a mixture of clay 20% to 60% by weight and subsequently baked to form a ceramic rod. An increase in the percentage of clay makes the pencil harder, so that smaller amount of graphite is place on the paper.
REDOX REACTION
from Femosky110 on 06/12/2020 01:24 PMREDOX REACTIONS
Here, we will discuss about the different definitions of oxidation and reduction (redox) in terms of oxygen transfer, hydrogen and electrons. We will as well talk about oxidizing agent and reducing agent.
Definitions of oxidation and reduction in terms of oxygen transfer
• Oxidation is addition of oxygen.
• Reduction is removal of oxygen.
For instance, in the extraction of iron from its ore:
Due to the fact that reduction and oxidation are going on side-by-side, this is known as a redox reaction meaning oxidation-reduction reaction.
Oxidising and reducing agents
chemistry
An oxidizing agent is a substance that oxidizes another thing else. In the example above, the iron (III) oxide is the oxidizing agent.
A reducing agent is a substance that reduces something else. In the above equation, the carbon monoxide is acting as the reducing agent.
• Oxidizing agents provide oxygen to another substance.
• Reducing agents take out oxygen from another substance.
Oxidation and reduction in terms of hydrogen transfer
• Oxidation is the loss of hydrogen from a compound.
• Reduction is gain of hydrogen by a compound.
These definitions you would notice are precisely the reverse of the definition of oxidation and reduction in terms of oxygen.
For instance, ethanol can be oxidized to ethanal:
In other to remove the hydrogen from the ethanol, you would need to make use of oxidizing agent. A regularly used oxidizing agent is potassium dichromate (VI) solution that is acidified with dilute sulphuric acid.
Ethanal can as well again be reduced back to ethanol through the addition of hydrogen to it. A potential reducing agent is sodium tetrahydridoborate, NaBH4. Again, the equation is excessively complex to be worth troubling about at this level.
As a summary:
• Oxidizing agents provide oxygen to a different substance or take away hydrogen from it.
• Reducing agents take away oxygen from another substance or provide hydrogen to it.
Oxidation and reduction in terms of electron transfer
• This is simply the most significant application of the oxidation and reduction at A' level.
• Oxidation is defined as electron loss.
• Reduction is defined as electron gain.
It is necessary that you have these definitions in mind. There is a extremely simple way to accomplish this.
An example is shown below:
The equation illustrates an uncomplicated redox reaction which can perceptibly be explained in terms of oxygen transfer.
Copper (II) oxide and magnesium oxide are mutually ionic. The metals evidently are not. If you rephrase this as an ionic equation, it turns out that the oxide ions are bystander ions that you are left with:
A last remark on oxidizing and reducing agents
In the equation above, the magnesium is reducing the copper (II) ions by donating electrons to them to neutralize the charge. Magnesium is acting as a reducing agent.
Looked at in another way, the copper (II) ions are extracting electrons from the magnesium to generate the magnesium ions. The copper (II) ions are working as an oxidizing agent.
Oxidizing and Reducing Agents
An oxidizing agent or oxidant is a substance that gains electrons and is reduced in a chemical reaction. The oxidizing agent is also known as electron acceptor, the oxidizing agent is usually in one of its top probable oxidation states due to the fact that it will gain electrons and be reduced. Examples of oxidizing agents are halogens, potassium nitrate, and nitric acid.
A reducing agent or reductant is a substance that loses electrons and is oxidized in a chemical reaction. A reducing agent is normally in one of its lesser possible oxidation states and is referred to as the electron donor. A reducing agent would normally be oxidized due to the fact that it loses electrons in the redox reaction. Examples of reducing agents are the earth metals, formic acid, and sulfite compounds.
A reducing agent reduces other substances and loses electrons; consequently, its oxidation state will amplify. An oxidizing agent oxidizes other substances and gains electrons consequently; its oxidation state will lessen.
How to balance Oxidation-Reduction Equations
Trial-and-error approaches to balancing chemical equations entails playing with the equation amending the ratio of the reactants and products till the objectives below have been attained.
Objectives for Balancing Chemical Equations
1. The number of atoms of every element on both sides of the equation is identical and as a result mass is conserved.
2. The sum of the positive and negative charges ought to be the same on both sides of the equation and consequently charge is conserved. Charge is conserved due to the fact that electrons are neither created nor destroyed in a chemical reaction.
There are two scenarios where depending on trial and error can put you into trouble. Sometimes, the equation is extraordinarily complex to be calculated by trial and error within a realistic amount of time. Think about the following reaction, for instance.
3 Cu(s) + 8 HNO3(aq) 3Cu2+(aq) + 2 NO(g) + 6 NO3-(aq) + 4 H2O(l)
Sometimes, more than a single equation can be printed that looks as it is balanced. The subsequent equations are just a handful of the balanced equations that can be written for the reaction between the permanganate ion and hydrogen peroxide, for instance.
2 MnO4-(aq) + H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 3 O2(g) + 4 H2O(l) 2 MnO4-(aq) + 3 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 4 O2(g) + 6 H2O(l) 2 MnO4-(aq) + 3 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 5 O2(g) + 8 H2O(l) 2 MnO4-(aq) + 7 H2O2(aq) + 6 H+(aq) 2 Mn2+(aq) + 6 O2(g) + 10 H2O(l)
Equations like these ought to be balanced by an additional methodical approach than trial and error.
Eletrochemical cells
Galvanic and Electrolytic Cells
Oxidation-reduction reaction or redox reactions occur in electrochemical cells. There are two different kinds of electrochemical cells. Spontaneous reactions take place in galvanic (voltaic) cells; non-spontaneous reactions take place in electrolytic cells. The two types of cells have electrodes where the oxidation and reduction reactions take place. Oxidation takes place at the electrode referred the anode and reduction takes place at the electrode known as the cathode.
Electrodes and Charge
The anode of an electrolytic cell is positive electrode while cathode is negative electrode, since the anode pull anions towards you from the solution. Nevertheless, the anode of a galvanic cell is negatively charged, since the spontaneous oxidation at the anode is the basis of the cell's electrons or negative charge. The cathode of a galvanic cell is its positive pole. In the 2cells- galvanic and electrolytic cells, oxidation occurs at the anode and electrons movement is from the anode to the cathode.
Galvanic or Voltaic Cells
The redox or reduction-oxidation reaction in a galvanic cell is a spontaneous reaction. Therefore, galvanic cells are normally used as batteries. Galvanic cell reactions provide energy which is utilized to carry out work. The energy is harvested by positioning the oxidation and reduction reactions in different containers, connected by an apparatus that permits electrons to flow. A widespread galvanic cell is the Daniell cell, illustrated below.
chemistry
Electrolytic Cells
The redox reaction or reduction-oxidation reaction in an electrolytic cell is non spontaneous. Electrical energy is needed to stimulate the electrolysis reaction. A sample of an electrolytic cell is illustrated below with a molten NaCl that is electrolyzed to form liquid sodium and chlorine gas. The sodium ions wander toward the cathode, the electrode at which they are reduced to sodium metal. Likewise, chloride ions move to the anode and are oxidized to form chlorine gas. This sort of cell is used to generate sodium and chlorine. The chlorine gas can be gathered near the cell. The sodium metal is less heavy than the molten salt and is therefore taken away as it floats to the apex of the reaction container.
Electrolysis is the passage of a direct electric current through an ionic compound that is either in molten form or dissolved in an appropriate solvent, leading to chemical reactions at the electrodes and disconnection of materials.
The major components necessary to attain electrolysis are :
• An electrolyte : An electrolyte is a substance that contains free ions that are the carriers of electric current in the electrolyte. If the ions are not in motion like in a solid salt electrolysis cannot take place.
• A direct current (DC) supply: makes available the energy required to generate or discharge the ions in the electrolyte. Electric current is carried by electrons in the external circuit.
• Two electrodes: Electrodes are electrical conductor that produces the physical boundary between the electrical circuit making available the energy and the electrolyte.
Electrodes of metal, graphite and semiconductor substance are extensively used. Selection of appropriate electrode depends on chemical reactivity between the electrode and electrolyte and the asking price of production.
Process of electrolysis
The main process of electrolysis is the substitution of atoms and ions through the removal or addition of electrons from the external circuit. The preferred products of electrolysis are frequently in a dissimilar physical state from the electrolyte and can be separated by a number of physical processes. For instance, in the electrolysis of brine that yields hydrogen and chlorine, the resulting product are gaseous. These gaseous products bubble from the electrolyte and are collected.
2 NaCl + 2 H2O → 2 NaOH + H2 + Cl2
A liquid containing mobile ions (electrolyte) is manufactured by:
• Solvation or reaction of an ionic compound with a solvent like water to give rise to mobile ions.
• An ionic compound is dissolved or merged by heating
An electrical potential is applied crosswise a pair of electrodes engrossed in the electrolyte.
Every one of the electrodes attracts ions that have differing charge. Positively charged ions (cations) move towards the electron-supplying (negative) cathode, while negatively charged ions (anions) drift towards the positive anode.
At the electrodes, electrons are taken or given out by the atoms and ions. Those atoms that gain or lose electrons to turn into charged ions move into the electrolyte. Those ions that gain or lose electrons to turn into uncharged atoms split from the electrolyte. The production of uncharged atoms from ions is referred to as discharging.
The energy that is needed to make the ions to travel to the electrodes, and the energy to result to the change in ionic state, is made available by the external supply of electrical potential.
Oxidation and reduction at the electrodes
Oxidation of ions or neutral molecules takes place at the anode, and the reduction of ions or neutral molecules takes place at the cathode. For instance, it is probable to oxidize ferrous ions to ferric ions at the anode:
Fe2+ aq → Fe3+ aq + e-
It is as well likely to reduce ferricyanide ions to ferrocyanide ions at the cathode:
Fe(CN)3-6 + e– → Fe(CN)4-6
RATE OF REACTION
from Femosky110 on 06/12/2020 01:22 PMRates Of Reactions And Equilibrium Of Reacting Systems
Chemical equilibrium in a chemical reaction is the condition in which both reactants and products are present at concentrations that have no extra propensity to alter with time. Characteristically, this situation arises when the rate of forward reaction is equal to the rate of backward reaction. The rate of forward and backward reaction is not normally zero at this point but is equal. What this means is that there is no net alterations in the concentrations of the reactant(s) and product(s). A situation like this is referred to as dynamic equilibrium.
Reversible reactions
A reversible reaction is a reaction which can proceed at either direction depending on the situations.
If you pass steam over hot iron, you would notice a reaction between the steam and the iron to produce a black, magnetic oxide of iron referred to as triiron tetroxide, Fe3O4
The hydrogen that is manufactured during the reaction is carried away by the stream of steam.
Under various situations, the products of this reaction will as well react together. The Hydrogen that is made to pass over hot triiron tetroxide reduces it to iron. Steam is also manufactured.
At this juncture the steam produced in the reaction is taken away by the stream of hydrogen.
These reactions occur simultaneously either ways and are reversible, but under the conditions usually used, they turn out to be one-way reactions.
Reversible reactions taking place in a closed system
A closed system is a system is a reacting system in which no substances are added to the system or lost from it. Energy can, nevertheless, be transmitted in or out freely.
If we consider the example we've considering above, imagine that iron is being heated in steam in a closed container. The system is being heated up but none of the substances in the reaction can break out because the system is closed. As the amount of triiron tetroxide and hydrogen begin to be formed, they would in turn react again to produce the original iron and steam. Therefore, if you analyzed the mixture after sometime you would notice a situation referred to as a dynamic equilibrium.
In a nutshell, a dynamic equilibrium takes place when a reversible reaction occurs in a closed system. The system remains unchanged except that energy would be added to it. When the reaction is at equilibrium, the amount of all that is available in the mixture remains unchanged even though the reactions are still progressing. This situation arises due to the fact that at this point, the rate of forward reaction is equal to the rate of backward reaction.
If there is any alteration in the conditions to the extent that it alters the relative rates of the forward and backward reactions, the position of equilibrium is shifted to annul the changes in the conditions.
Reaction Rate or rate of a chemical reaction
The rate of a chemical reaction or Reaction Rate is the estimation of the alteration in concentration of the reactants or the alteration in concentration of the products over a unit time.
For an example, during the chemical reaction between products A and B as shown in the equation below, the reactants A and B are used up while the concentration of product AB increases. The reaction rate or rate of the chemical reaction can be measured by estimating how fast the concentration of A or B is being used up, or by how fast the concentration of AB is being formed.
A + B ---- AB
For the purpose of stochiometry, the above equation can be further represented as:
aA + bB ------ cC+ dD
Collision Theory
The collision theory states that gaseous state chemical reactions takes place when two gas molecules smash together with enough kinetic energy. The smallest amount of energy that is needed for a thriving collision, which leads to a successful reaction, is referred to as the activation energy. Consequently, only a fraction of collisions result to successful reactions.
The collision theory is derived from the kinetic theory of gases. Thus we are only dealing with gaseous chemical reactions. Because of this, the ideal gas assumptions are applied. Moreover, we are as well making assumptions that:
1. All the reacting molecules are moving through space in a straight line.
2. All molecules are inflexible spheres.
3. The reactions being discussed only takes place between two molecules.
4. The molecules ought to collide with one another.
In the end, the collision theory of gases offers us the rate constant for bimolecular gaseous reactions; it is equal to the rate of winning collisions. The rate of successful collisions is proportional to the small part of successful collisions multiplied by the general collision frequency.
Collision Frequency
The rate or frequency at which molecules collide is referred to as the collision frequency, Z. The unit of collision frequency is collisions/ unit of time. Given a box of molecules A and B, the collision frequency between molecules A and B is given by:
Successful Collisions
To enable a successful collision to take place, the molecules of the reactant ought to collide with sufficient kinetic energy to break original bonds and be able to form fresh bonds to turn into the molecules of the product. Therefore, it is referred to as the activation energy for the reaction; it is as well normally regarded as the energy barrier.
The portion of collisions that possess sufficient energy to exceed the activation barrier is denoted as:
The tiny proportion of successful collisions is directly proportional to the temperature and inversely proportional to the activation energy of the reaction.
In conclusion
The rate constant of a gaseous reaction is proportional to the product of the collision frequency and the fraction of successful reactions. Just like we mentioned above, enough kinetic energy is necessary for a successful reaction; but they need to appropriately.
The Activation Energy of Chemical Reactions
Only a minute portion of the collisions between reactant molecules change the reactants into the products of the chemical reaction. This can be understood by considering the reaction between ClNO2 and NO.
ClNO2(g) + NO(g) NO2(g) + ClNO(g)
During the process of this reaction, a chlorine atom is transmitted from one nitrogen atom to another. To enable the reaction to occur, the nitrogen atom in NO have to bump with the chlorine atom in ClNO2
The reaction will not take place if the oxygen end of the NO molecule collides with the chlorine atom on ClNo2
It will also not take place if an oxygen atom from among the 2 atoms on ClNO2 collides with the nitrogen atom on NO.
An additional factor that determines if a reaction will take place is the energy the molecules carry or bears the moment they come in contact for collision. It is not every molecule that possesses the same kinetic energy. This is significant for the reason that the kinetic energy molecules bear the moment they bump is the most important basis of the energy that ought to be invested in a reaction to make it to occur.
The total typical free energy for the reaction between ClNO2 and NO is favorable.
ClNO2(g) + NO(g) NO2(g) + ClNO(g) Go = -23.6 kJ/mol
But, prior to the reactants being converted into products, the free energy of the system ought to conquer the activation energy for the reaction.
All molecules have a definite minimum quantity of energy. The energy can either be in the form of Kinetic Energy and/or Potential Energy. When molecules come in contact with one another, the kinetic energy of the molecules can be made use of to elongate, twist, and eventually break bonds, resulting to chemical reactions. If molecules are travelling too unhurriedly with a small kinetic energy, or they collided with an inappropriate direction, they will not lead to reaction and would merely bounce away from each other. Nevertheless, if the molecules are travelling at a swift speed sufficient to cause a successful collision orientation, in a manner that the kinetic energy on collision is higher than the minimum energy barrier, then a reaction will take place. The minimum energy obstruction that ought to be achieved for a chemical reaction to occur is known as the activation energy; Ea. Ea is normally in units of kilojoules per mole.
Activation energy, Enthalpy, Entropy and Gibbs Energy
In Thermodynamics, Gibbs free energy change, ΔG, is defined as:
ΔG=ΔH −TΔS
where
• ΔG = Gibbs free energy change of the reaction
• ΔH = Enthalpy change of the reaction
• ΔS = Entropy change of the reaction.
ΔGo is the Gibbs energy change when the reaction takes place at Standard State (1 atm, 298 K, pH 7).
To calculate a change in Gibbs free energy of the reaction that did not occur at a standard state, the Gibbs free energy equation can be denoted as:
ΔG = ΔGo + RTlnk
where
• ΔG = Gibbs free energy change of the reaction
• ΔGo = standard Gibbs free energy of the reaction
• R = 8.314 J/molK
• k = equilibrium constant
At equilibrium, ΔG=0. The equation above then becomes:
0= ΔGo + RTlnk
Solve for ΔGo
ΔGo = −RTlnk
Dynamic Equilibrium
At dynamic equilibrium, reactants are transformed to products and products are transformed to reactants at an equivalent and constant rate. An example of a reaction in dynamic equilibrium is the dissociation of acetic acid. For instance
CH3COOH ---- H+ + CH3COO-
Static Equilibrium
Static equilibrium is as well referred to as mechanical equilibrium. It takes place when all particles in the reaction are at rest and there is no movement between reactants and products. Static equilibrium can as well be experienced in a steady-state system in a physics-based outlook.
Dynamic forces are not performing on the potential energies of the backward and forward reactions. One example of static equilibrium is graphite changing into diamond. This reaction is well thought-out at static equilibrium after it takes place for the reason that there is no more forces acting upon the reactants (graphite) and products (diamond).
Le Chatelier's Principle and Equilibrium
Equilibrium can be explained through the Le Chatelier's principle. The kinetics of a reaction can alter and the position of equilibrium would depend on the properties of the reactants and products. Put in a simpler way, the equilibrium will swing towards one side or the other relative to the concentration, temperature, pressure, and volume. Le Chatelier's principle is not the same thing as dynamic equilibrium. Although they are comparable, they are of variable concepts. Le Chatelier's principle explains the way equilibrium can alter. Dynamic and static equilibrium explain the way systems in equilibrium behave.
Comparison between Dynamic and Static Equilibrium
A reaction at dynamic equilibrium has the capability to be reversible while a reaction at static equilibrium is irreversible. The equilibrium constant alone cannot determine if a reaction is in static or dynamic equilibrium due to the fact that the equilibrium constants are estimated through the concentrations of products against reactants. A reaction is at dynamic equilibrium if the rate of the forward reaction is the same as the rate of the backward reaction. It is at static equilibrium if the reaction has taken place and there is no forward or backward rate of reaction.
SOLUBILITY OF SUBSTANCES
from Femosky110 on 06/12/2020 01:20 PMSOLUBILITY OF SUBSTANCES
The solubility of a substance is the amount of a substance that will dissolve in a given amount of a solvent. Solubility is a quantitative term. Solubility of substance differs greatly. The terms soluble and insoluble are comparative. A compound is termed soluble if more than 0.1g of that compound dissolves in 100 mL of solvent. If less than 0.1 g of the compound dissolves in 100 mL solvent, the compound is said to be insoluble or sparingly soluble. The terms miscible and immiscible liquids that are encountered when describing the solubility of a liquid in another mean: a liquid is miscible when it is soluble beyond measure for instance alcohol is miscible with water. A liquid is immiscible or insoluble means the same thing; oil is said to be immiscible with water, as in oil and vinegar salad dressing.
Determination of Solubility
To determine solubility, a known amount of a solvent such as 100 mL is put in an urn after which the substance whose solubility is to be calculated is added until the substance is unable to dissolve again even when stired vigorously and left to stand for a long period of time. Such a solution is said to be saturated meaning that it contains as much solute that it could dissolve at that temperature.
Saturated solutions
A saturated solution is a solution that contains the dissolved solute in equilibrium.
Dissolution and precipitation occurs at the same rate, thus satisfying the condition for a dynamic equilibrium. This condition was set forth when discussing the equilibrium between liquid and vapor. We can convey equilibrium condition in sucrose solution for an example with the equation below:
chemistry
Sucrose(s) ----- Sucrose(aq)
Two deductions that can be made from the equations are that the two processes of dissolution and precipitation are taking place concurrently and that the number of molecules in the solution remains unchanged.
The saturated solution of an ionic compound differs a little from the saturated solution of covalent compounds such as sucrose. The ionic compound melts and stays in solutions as ions while the covalent compound melts and remains in solutions as molecules. The equilibrium of sodium chloride with its ions in a saturated solution is demonstrated with the following equation:
NaCl(s) Na+(aq) + Cl-(aq)
An unsaturated solution normally has smaller amount of solute than a saturated solution. There is nothing like equilibrium in an unsaturated solution. Such a solution would normally take up and dissolve any additional solute that is added to it. On the contrary when you add an extra amount of solute to a saturated solution, no additional number of solute would be dissolved because it has reached the boundary of its solubility. Any extra solute added to a saturated solution would merely amplify the amount of undissolved solute.
It is worth noting that solubility alters with temperature. A solution that is saturated at a particular temperature may be unsaturated at another temperature.
Again, dissolution requires interaction between the molecules (or ions) of the solute and the molecules of the solvent. A thinly divided solute will dissolve more quickly than when it is larger due to the fact that it provides a better contact between the dissolving solute and solvent. Constant stirring also increases the rate of dissolution, due to the fact that stirring alters the particular solvent molecules that are come in contact with undissolved solute. Solubility of solids and liquids characteristically increases with increase in temperature, therefore, temperature, solids and liquids are frequently dissolved in warm solvents.
Factors affecting solubility of substance
There are a lot of factors that affect the solubility of a substance in another. Some of them are: temperature, polarity, pressure, and molecular size.
1. Forces between particles
The nature of intermolecular forces in both the solute and the solvent determines the rate of solubility between them. When a substance dissolves in another, it must overcome the attractive forces between two of them. The dissolving solute ought to be able to break up the aggregation of molecules in the solvent. This means overcoming the hydrogen bonds between the molecules or the dispersion forces between molecules in a non-polar solvent. The molecules of the solvent must therefore have enough attraction for the particles of the solute to take them away one after another from their neighbors in the undissolved solute. If the solute is ionic, only an extremely polar solvent such as water provides enough interaction to result to dissolution. If the solute particles are polar molecules, they are easily dissolved in polar solvents like alcohols. Non polar solute on the other hand dissolves in non-polar solvents. The reason is not because polar solvent molecules cannot conquer the weak dispersion forces between the solute molecules, but due to the fact that these dispersion forces are extra ordinarily weak to overcome the dipole-dipole interaction that exists between the solvent molecules.
Generally, like dissolves like. Ionic and polar compounds are soluble in polar solvents like water or liquid ammonia. Nonpolar compounds are soluble in non-polar solvents, like carbon tetrachloride, and hydrocarbon solvents like gasoline.
The solubility of gases in water depends very much how polar the gas molecules are. Those gases whose molecules are polar are much more soluble in water than non-polar gases. Ammonia, a highly polar molecule, is extremely soluble in water (89.9 g/100 g H2O) and hydrogen chloride (82.3 g/100 g H2O). Helium and nitrogen are nonpolar molecules. Helium is mere partially soluble (1.8 X 10-4 g/100 g H2O), like in nitrogen (2.9 X 10-3 g/100 g H2O)
Solubility and inter-particle bonds in various types of compounds and their relative solubilities in water, a polar solvent; in alcohol, a less polar solvent; and in benzene, a non-polar solvent
Kinds of bonds Example Water Alcohol Benzene
ionic sodium chloride very soluble slightly soluble insoluble
polar covalent sucrose (sugar) very soluble soluble insoluble
nonpolar covalent napthalene Insoluble soluble very soluble
2. Temperature
The solubility of substances varies at different temperature. Usually, the solubility of solids and liquids rises at higher temperature but the solubility of gases diminishes with an increase in temperature. This property of gases causes is a great concern for the life of fishes in lakes, oceans, and rivers. Fish needs dissolved oxygen to stay alive. If the temperature of their water habitat increases, the concentration of dissolved oxygen is reduced and the life of the fishes is at stake.
3. Pressure
The pressure on the surface of a solution has less effect on the solubility of solids and liquids but a great effect on the solubility of gases.
Solubility Curve:
A solubility curve is a measurement shown on a graph that is utilized to establish the mass of a given dissolved item like salt or sugar in 100ml of water. The substance that is that is dissolved in the water is called a solute. If a figure falls under the line on the graph, it denotes an unsaturated solution which has the capacity to take up more solute.
Solubility curves permit a scientist to establish the amount of a solute that can dissolve in 100 grams of water at a specific temperature.
The Graph below shows the Grams of solute per 100g of water against temperature (°C)
A steeper slope shows the increased effect on solubility by temperature rise.
Solid Solutes against Gas Solutes: As the temperature rises, the solubility of a solid rises and solubility of gases decrease.
A sample question:
1. What is the quantity of sodium chloride that can be dissolved in 100 mL of water at 30°C?
2. At 20°C, the highest amount of potassium chlorate is dissolved in 100 g of water. When the temperature is increased to 50°C, how much more potassium chlorate can be dissolved in the water?
The amount of potassium chloride that can be dissolved in 50 mL of water at 50°C can be estimated as follows
Application of solubility product principle in qualitative analysis
The concepts of solubility of product and the common effect of ion are greatly employed in the process of qualitative analysis to separate essential radicals or cations into various groups.
Weak acids and weak bases ionise partially in water leading to an equilibrium situation being attained in their solutions. For instance, in the ionization of a weak base NH4OH shown below:
The ionization constant for the base is
Qualitative analysis
The widespread effect of ion is usually employed in qualitative analysis.
The cations of group II elements (Hg2+, Pb2+, Bi3+, Cu2+, As3+, Sb3+, Sn2+) are normally precipitated as their sulphides for example the CuS and PbS through the passage of H2S gas in the presence hydrochloric acid which possesses the common H+ ions.
The cations of group III elements are precipitated in their hydroxides forms by NH4OH in the presence of NH4Cl.
The cations of group V are precipitated in their carbonates forms through the addition of (NH4)2CO3, in the presence of HCl.
In relation to solubility, salts can be classified into three main types:
1. Soluble salts ie salts with their solubility greater than 0.1 M
2. Slightly soluble salts that is salts with solubility in the range of 0.01 M and 0.1 M
3. Sparingly soluble salt ie salts with solubility less than 0.01 M
Crystallization
Crystallization is a procedure which chemists employ to purify solid compounds. It is one of the essential procedures every chemist ought to master to become capable in the laboratory. Crystallization is based on the principles of solubility.
The difference between crystallization and solubility
Solubility is the capability to dissolve in a solvent. It is measured in units g per 100mL of solvent. Crystallization is the process through which crystals are formed. This could be from a molten substance but is normally from a solvent. As the solvent evaporates
Solution
A solution is a homogenous mixture of two or more substances.
There are two components of a solution-
Solute and solvent
Solution = solute + solvent
Solute
A solute is the constituent of a solution that is in little quantity.
Solvent
A solvent is the constituent of solution that is in greater quantity.
Saturated solution-
Is a solution that can hold no more of the solute at a specific temperature.
An Unsaturated solution-
An unsaturated solution is a solution, which contains less amount of solute than is required to saturate it at that temperature.
A super saturated solution-
Is a solution that is more concentrated than a saturated solution. When an extra crystal of solute is added to the solution, the surplus solute forms crystal.
An aqueous solution-
Is a solution of any substance in which the solvent is water.