A chemistry team is evaluating three galvanic cells that could be used to power a…

CHEMISTRY · Multi-part · A Level · Chemistry · Electrode potentials · Electrode potentials

Problem

A chemistry team is evaluating three galvanic cells that could be used to power a portable medical sensor. The cells are constructed by combining the half-reactions in the data table below. Standard Reduction Potentials (298 K)

Half-Reaction	$E^{\circ}_{\text{red}}$ (V)
$\text{Ag}^+ + e^− \rightarrow \text{Ag}$	$+0.80$
$\text{Sn}^{2+} + 2e^− \rightarrow \text{Sn}$	$−0.14$
$\text{Fe}^{3+} + e^− \rightarrow \text{Fe}^{2+}$	$+0.77$
$\text{Zn}^{2+} + 2e^− \rightarrow \text{Zn}$	$−0.76$

(a) For each of the following overall reactions carried out under standard conditions, write the balanced equation and determine the standard cell potential,

E^{\circ}_{\text{cell}}

. (i) Silver ion reduced by solid zinc (ii) Iron(III) ion reduced by solid tin (iii) Silver ion reduced by solid tin (b) Rank the three overall reactions from most thermodynamically favorable to least thermodynamically favorable based on your calculated

E^{\circ}_{\text{cell}}

values. If any pair of reactions appears equally favorable from the standpoint of

E^{\circ}_{\text{cell}}

, identify that tie clearly. (c) For any tie you identified in part (b), compare the number of electrons transferred,

n

, for those reactions. Explain how

n

can be used to resolve the tie when assessing the magnitude of

\Delta G^{\circ}

for each reaction.

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