Question

In Electrolysis of Water experiment, water (H2O) is being broken down into H2 and O2. How do the volumes of gas tell you which gas is produced from which electrode?

Why is it important for the circuit that the water used in the Hoffman apparatus contains an electrolyte (dissolved ions — usually a salt or a strong acid)?

Answer 1

The hydrolysis of water will yields

2H2O(l) ------ 2H2(g) + O2(g)

The oxidation state of Oxygen is changing from -2 to 0, which means oxygen is getting oxidized and H2 is getting reduced, so the oxygen will come from anode and H2 gas will come from electrode.

Other Method:

2 moles of H2O will gives 1 moles of O2 and 2 moles of H2. Hence the gas with less volume is the O2 gas and gas with higher volume is H2 gas

Question 2:

The pure water cannot conduct electricity because the concentration of [H+] = [OH-] = 10^(-7) which is very less. But with the addition of electrolytes, the substance dissociates in water which can be used to carry the current and proceed the reaction in the forward direction