CBSE Class 10 Answered

Electrolysis of Acidified Water

Electrolyte: Acidified water

Electrodes:

Anode: Platinum

Cathode: Platinum

Ionisation of acidified water: H₂O  → H⁺ + OH^–

                                              H₂SO₄  → 2H⁺ + SO₄^2–

Ions present: H⁺, SO₄^2–, OH^–

Electrode reactions: 

Reaction at the cathode: H+ + e⁻ → H

                                         H + H → H₂ (hydrogen molecule)

Reaction at the anode: OH^– − e⁻  → OH × 4

OH– ion discharge in preference to SO₄^2–

                  4OH → 2H₂O + O₂ (oxygen molecule) 

At the cathode, Hydrogen gas is evolved and at the anode, oxygen gas is liberated.

The water molecule has two atoms of hydrogen and one atom of oxygen, that means in the no. of hydrogens are double than that of oxygen,

hence the amount of hydrogen gas evolved collected in one of the test tubes doubles the amount in the other gas i.e., oxygen.