Neco 2018 Chemistry Question 10

An aqueous solution containing 0.500 mol of NaCl is electrolysed using a graphite anode and a platinum cathode. A constant current of 12.0 A is passed for 2.00 h. At the cathode the possible reductions are \(\text{Na}^{+} + e^{-} \rightarrow \text{Na(s)}\) \((E^{\circ} = -2.71\ \text{V})\) and \(2\text{H}_2\text{O} + 2e^{-} \rightarrow \text{H}_2 + 2\text{OH}^{-}\) \((E^{\circ} = -0.83\ \text{V})\). Assuming the more favourable reaction occurs, calculate (i) which product is formed at the cathode, (ii) the theoretical mass of \(\text{H}_2\) that could be produced, and (iii) the actual mass of \(\text{H}_2\) obtained if the current efficiency is 85 %. Express the actual mass in grams and the percentage of the theoretical maximum obtained.