Consider the following standard electrode potentials:

\[\begin{array}{*{20}{l}} {{\text{S}}{{\text{n}}^{4 + }}{\text{(aq)}} + {\text{2}}{{\text{e}}^ - } \rightleftharpoons {\text{S}}{{\text{n}}^{2 + }}{\text{(aq)}}}&{{E^\Theta } = + 0.13{\text{ V}}} \\ {{\text{P}}{{\text{b}}^{2 + }}{\text{(aq)}} + {\text{2}}{{\text{e}}^ - } \rightleftharpoons {\text{Pb(s)}}}&{{E^\Theta } = - 0.13{\text{ V}}} \end{array}\]

What is the value of the cell potential, in V, for the spontaneous reaction that occurs when the two half-cells are connected together?

A.     \( - 0.26\)

B.     0.00

C.     \( + 0.13\)

D.     \( + 0.26\)

D

One respondent stated that it would have been better if the electrode potential half equations had equilibrium signs as in the Data Booklet. It is true that they could have been represented in this way (though not necessarily). This certainly did not have an impact on the question itself. 74.77% of candidates got the correct answer D.