REDOX REACTION

REDOX REACTION

from Femosky110 on 06/12/2020 01:24 PM

REDOX 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