NEAP 2010 Question

[toshibaj]

Question 14

The following reaction is used in a number of experiments investigating galvanic cells:
Ag+(aq) + Fe2+(aq) Ag(s) + Fe3+(aq)

A disc of silver is used as one electrode and a carbon rod is used as the other electrode. When various
concentrations of ions were used in the galvanic cell, the following results were recorded.

Experiment 4: Concentration of Fe3+ is 0.00033M, [Fe2+] is 0.01M, [Ag+] is 0.01M, anode is neither carbon nor silver, EMF = 0.

In experiment 4, the anode could not be identified because:

A. all the reactants had been consumed, leading to the cell not producing any voltage.
B. both the oxidation and reduction reactions had ceased, resulting in zero voltage in the cell.
C. the cell reaction had reached equilibrium, yielding no net reaction in the cell.
D. the products in the cell had built up to an extent which hindered the operation of the cell.


The answer is C. I was just wondering, how can it reach equilibrium? I was under the impression that because half-cells are separated, reverse reactions do not occur.

Thanks

[Mao]

Reverse reactions always occur, but you only see the 'overall' flow of electrons.