Q21 / 160 · TS EAMCET 2023 (12 May Shift 1) · Chemistry

The electrode potential of chlorine electrode is maximum, when the concentration of chloride ion in the solution (in $\left.\mathrm{mol} \mathrm{L}^{-1}\right)$ is $\mathrm{X}$. What is the value of $\mathrm{X}$ ?

  • Correct answer
    A
    $2.5 \times 10^{-3}$
  • B
    $7.5 \times 10^{-3}$
  • C
    $7.5 \times 10^{-2}$
  • D
    $2.5 \times 10^{-2}$

Solution

The nernst equation for reduction potential of an electrode is ;- $\mathrm{E}=\mathrm{E}^{\circ}-\frac{2.303 \mathrm{RT}}{\mathrm{nF}} \log \frac{\left[\mathrm{Cl}^{-}\right]}{\mathrm{P}_{\mathrm{Cl}_2}}$ or, $\mathrm{E}=\mathrm{E}^{\circ}-\frac{0.0591}{2} \log \frac{\left[\mathrm{Cl}^{-}\right]}{\mathrm{P}_{\mathrm{Cl}_2}}$ Thus the reduction/electrode potential will be highest for the lowest concentration of $\mathrm{Cl}^{-}$ions. The lowest concentration of $\mathrm{Cl}^{-}$is $2.5 \times 10^{-3} \mathrm{M}$. Thus, $\mathrm{x}=2.5 \times 10^{-3}$.

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

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