Electrochemistry - Result Question 103
####51. Consider the cell,
$$ Zn\left|Zn^{2+}(a q)(1.0 M) | Cu^{2+}(a q)(1.0 M)\right| Cu $$
The standard reduction potentials are $0.350 V$ for
$$ \begin{aligned} Cu^{2+}(a q)+2 e^{-} & \longrightarrow Cu \ \text { and }-0.763 V \text { for } Zn^{2+}(a q)+2 e^{-} & \longrightarrow Zn \end{aligned} $$
(i) Write down the cell reaction.
(ii) Calculate the emf of the cell.
(iii) Is the cell reaction spontaneous or not?
$(1982,2 M)$
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Solution:
- (i) The cell reaction is
$$ Zn+Cu^{2+} \longrightarrow Zn^{2+}+Cu $$
(ii) $E _{\text {cell }}^{\circ}=E _{\text {cathode }}^{\circ}-E _{\text {anode }}^{\circ}=0.350-(-0.763)=1.113 V$
$\because$ Both $Zn^{2+}$ and $Cu^{2+}$ are at unit concentrations,
$$ \begin{aligned} & E=E^{\circ}=1.113 V \ & \text { (iii) } \because \quad E _{\text {cell }}=1.113 V>0 \end{aligned} $$
Therefore, the cell reaction is spontaneous.
