Electrolysis is a process in which Electrical energy is converted into Chemical Energy, and a non-spontaneous chemical reaction is carried out.

  • Direct current is used to carry out the process.
  • It can also be stated as a process in which solutions containing free ions are broken down.

Real-life usage of Electrolysis: Extraction of metals, Refining of metals, Manufacture of Chlorine, etc.

Electrolyte: All substances cannot conduct electricity. Electrolytes are those substances whose atoms are closely bonded, but when dissolved in water, the molecules split into free positive ions and negative ions called cation and anion, respectively.

  • Electrolytes can be an aqueous solution of acid, alkali, or molten metal.
  • These are of three types: Weak, Strong, and Non-Electrolytes.

Electrodes: Rods made up of inert conducting material that allow the passage of electricity through an electrolytic solution are called Electrodes. Generally, metal rods are used in cells.

  • Cathode refers to the rod connected to the negative terminal of the electric source. 
  • Anode refers to the rod connected to the positive terminal of the electric source.

If you want to understand Products of Electrolysis, you have to understand Electrolytic cells,

In an Electrolytic cell, when two electrodes are partly immersed in an electrolytic solution and an electric potential difference is applied ;

  • The free positive ions move towards the Cathode while,
  • The free negative ions move towards the Anode.

The positive ions get electrons from the Cathode and are reduced, and the negative ions give electrons to the Anode and are oxidised.

These are the products of electrolysis.

Let us understand this with some examples:

  1. Electrolysis of Molten NaCl
  2. Electrolysis of Aqueous NaCl
  3. Electrolysis of Water

1. Electrolysis of Molten NaCl

Electrolyte: Molten NaCl, conductor of electricity.

  • NaCl in solid form is inactive, and the atoms are closely linked, whereas 
  • Molten NaCl consists of Na+ and Cl- atoms

Electrode: A set of Inert Electrodes

When an electric current is applied to the molten NaCl, The Na+ ions move to the Cathode and Cl- ions move towards the Anode.

Liquid Na is produced at the cathode (-) 2Na+ + 2e- → 2Na

Gaseous Cl2 is produced at the anode (+) 2Cl- → Cl2 + 2e-

2Na+ + 2Cl- → 2Na + Cl2

Na(l) → Na(s)

This reaction is nonspontaneous below 801 degrees Celsius.

Products obtained are as follows:

  1. Chlorine gas, which is pale green and,
  2. Silvery Na floating above the molten NaCl is obtained.

The Sodium and Chloride should not be allowed to come in contact with each other as they react very spontaneously to form NaCl.

2. Electrolysis of Aqueous NaCl, i.e. Brine Solution

In an aqueous solution, the sequence of breaking down will be based on the stability of the solution, i.e., a more stable compound will be oxidised and reduced after the less stable compound.

You can understand this with the example of Electrolysis of Brine Water.

Electrolyte: Brine solution. This solution is NaCl in water. When NaCl is dissolved in water, Na+ and Cl- free ions are obtained and can conduct electricity.

When an electric current passes through the solution, water being less stable gets oxidised and reduced first.

At Cathode:

2H+(aq) + 2e- →H2(g)

2H2O + 2e- → H2(g)+2OH-. (aq)

At Anode:

Cl2 → 2Cl- +2e−

Na+ + OH- → NaOH

Products of Electrolysis:

  • At Cathode: H2 gas is obtained
  • At Anode: Cl2 gas and NaOH are obtained, Solid NaOH can be obtained by evaporation of the left solution.

Electrolysis is a very commercial and important process to produce Hydrogen gas, Chlorine gas and Sodium Hydroxide.

3. Electrolysis of Water

This is a very important and famous method to obtain Hydrogen Gas.

Electrolyte: Water (H2O) and a small amount of H2SO4, as water doesn’t have enough ions to carry out the reaction.

Products of Electrolysis:

Cathode: H2 bubbles (popping sound)

2{2H2O + 2e- → H2+ 2OH-} 

Anode: O2 bubbles (ember glows much brighter)

2H2O → O2 + 4H+ + 4e-

Overall reaction: 6H2O → 2H2+ 4H+ + 4OH- + O2

2H2O → 2H2 + O2

Factors Affecting the Product of Electrolysis

These are the major factors that affect the products of electrolysis.

Nature of Electrolyte

The efficiency of an Electrolysis reaction depends upon the nature of the electrolyte used. Strong electrolytes undergo the reaction at a faster speed compared to Weak electrolytes.

Type of Electrode

The primary function of the electrode is to pass electricity to the electrolyte solution without getting reduced or oxidised, which means it should not participate in the reaction. Electrodes made of Gold, Platinum, and polymers (inert electrodes) are preferred over-reactive electrodes.

Oxidising and Reducing Agents

In some processes, agents are added to catalyse the reactions, which can affect the products obtained in the reaction.

Electrode potential

The properties of the electrolytic products depend on the standard electrode potentials of the different reactants in the electrolyte. Multiple reactions may result in more than one product of electrolysis, which depends on the standard electrode potential of each reaction. 

Conclusion

With the help of this blog, you will witness the magic of chemicals. It covers all important

information regarding electrodes, electrolytes and the electrolysis of brine, NaCl, as well like

water. Also, learn about the most important part of electrolysis- the factors affecting the

products of electrolysis. You will surely enjoy this article and get to learn new things.