Q25 / 125 · BITSAT 2009 · Chemistry

In a cell that utilises the reaction $\mathrm{Zn}(\mathrm{s})+2 \mathrm{H}^{+}(\mathrm{aq}) \rightarrow \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g})$ addition of $\mathrm{H}_{2} \mathrm{SO}_{4}$ to cathode compartment, will

  • Correct answer
    A
    increase the $\mathrm{E}$ and shift equilibrium to the right.
  • B
    lower the $E$ and shift equilibrium to the right.
  • C
    lower the $E$ and shift equlibrium to the left.
  • D
    increase the $E$ and shift equilibrium to the left.

Solution

$\mathrm{Zn}(\mathrm{s})+2 \mathrm{H}^{+}+(\mathrm{aq}) \rightleftharpoons$ $$ \mathrm{Zn}^{2+}(\mathrm{aq})+\mathrm{H}_{2}(\mathrm{~g}) $$ $$ \mathrm{E}_{\mathrm{cell}}=\mathrm{E}^{\circ} \mathrm{cell}-\frac{0.059}{2} \log \frac{\left[\mathrm{Zn}^{2+}\right]\left[\mathrm{H}_{2}\right]}{\left[\mathrm{H}^{+}\right]^{2}} $$ Addition of $\mathrm{H}_{2} \mathrm{SO}_{4}$ will increase $\left[\mathrm{H}^{+}\right]$ and $\mathrm{E}_{\text {cell }}$ will also increase and the equilibrium will shift towards RHS.

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

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