Q25 / 160 · TS EAMCET 2019 (04 May Shift 1) · Chemistry

Consider the systems having liquid-solid interface, (A) copper wire in silver nitrate solution and (B) silver wire in copper sulphate solution. Predict which interface will show spontaneous reaction, if $$ E_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{~V} \text { and } E_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.80 \mathrm{~V} \text { ? } $$

  • Correct answer
    A
    Copper-silver nitrate interface
  • B
    Silver-copper sulphate interface
  • C
    There will be no spontaneous reaction
  • D
    Both interfaces will give spontaneous reaction

Solution

Spontaneous reaction can be determined on the basis of Gibbs free energy. $$ \Delta G^{\circ}=-n F E^{\circ} $$ $$ \begin{aligned} & E^{\circ}=E_c^{\circ}-E_A^{\circ} \\ & E_c^{\circ} \text { or } E_{\mathrm{Ag}^{+} / \mathrm{Ag}}^{\circ}=0.80 \mathrm{~V} \\ & E_A^{\circ} \text { or } E_{\mathrm{Cu}^{2+} / \mathrm{Cu}}^{\circ}=0.34 \mathrm{~V} \\ & E^{\circ}=0.80-0.34=0.46 \mathrm{~V} \\ & \Delta G^{\circ}=-n F E^{\circ}=-2 \times 96500 \times 0.46 \mathrm{~V} \end{aligned} $$ Hence, $\mathrm{Cu}-\mathrm{Ag}$ nitrate interface show spontaneous reaction due to-ve value of $\Delta G^{\circ}$.

Hence, the correct answer is option: 'A'.

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