The same quantity of electricity is passed through separate dilute aqueous solutions of sulfuric acid and copper(II) sulfate using platinum electrodes under the same conditions. Which statement is correct?

A.     The same volume of oxygen is obtained in both cases.

B.     The same volume of hydrogen is obtained in both cases.

C.     The amount of copper deposited at the negative electrode in the copper(II) sulfate solution is half the amount of hydrogen gas formed at the negative electrode in the sulfuric acid solution.

D.     The pH of both solutions increases as the electrolysis proceeds.

A

The most popular, but wrong, answer was C (42%) showing that candidates had not appreciated the formation of \({{\text{H}}_{\text{2}}}\). Many gave answer B but candidates should know that copper is deposited from aqueous solution. It is true that this question requires a lot of thought and it turned out to be the fourth most difficult question on the paper.