Question

The diagram given below is the apparatus for electrolysis of water. Identify A, B and C.

• A. A - Oxygen, B - Hydrogen, C - Copper plates
• B. A - Oxygen, B - Hydrogen, C - Platinum plates
• C. A - Hydrogen, B - Oxygen, C - Platinum plates
• D. A - Hydrogen, B - Oxygen, C - Copper plates

Answer 1

The correct option is C A - Hydrogen, B - Oxygen, C - Platinum plates

The chemical formula of water is ${\text{H}}_2\text{O}$. During its electrolysis, hydrogen gas is collected at cathode and oxygen gas at anode. This is because, during electrolysis of water, dissociates into hydrogen and oxygen ions.

The volume of hydrogen gas collected at cathode is double that of the oxygen gas collected at the anode. This is because water is made up of two volumes of hydrogen gas and one volume of oxygen gas.

So, A is hydrogen gas and B is oxygen gas. Platinum plates are used as electrodes in the electrolysis of water instead of copper since platinum is an inert electrode. Hence, C is platinum plate.