An aqueous solution of a metal salt is electrolysed. Which factor will have no effect on the mass of the metal deposited on the negative electrode (cathode), if all other variables remain constant?

A.     Size of metal ion

B.     Relative atomic mass of metal

C.     Current

D.     Charge on metal ion

A

Four respondents stated in their G2 forms that they teach that time, current and charge will affect the mass of metal deposited during electrolysis, but nothing about size of the metal ion or the relative atomic mass of the metal. Although charge is important when considering the deposition of Na, Mg and Al when the same amount of current for the same amount of time is used, the relative atomic mass becomes important when considering the deposition of metal with ions of the same charge, Na and K for example.

This proved to be one of the fifth most difficult question in the paper with 37.54% choosing the correct answer A and 36.8% opting for answer B. The discrimination factor in this question was 0.41.