Question

Given that the standard reduction potentials for $M^+/M$ and $N^+ /N$ electrodes at $298\, K$ are $0.52\, V$ and $0.25\, V$ respectively. Which of the following is correct in respect of the following electrochemical cell?
$M /M^+\left|\right| N^+ / N$

• A. The overall cell reaction is a spontaneous reaction
• B. The standard $EMF$ of the cell is $- 0.27\, V$
• C. The standard $EMF$ of the cell is $0.77\, V$
• D. The standard $EMF$ of the cell is $- 0.77\, V$
• E. The standard $EMF$ of the cell is $0.27\, V$

Answer 1

Answer: (B)

$ E_{\text {cell }}^{\circ} =E_{\text {cathode }}^{\circ}-E_{\text {anode }}^{\circ} $

$ =E_{\left(N^{+} / N\right)}^{\circ}-E_{\left(M^{+} / M\right)}^{\circ} $

$=(0.25-0.52) V =-0.27 V $

Since, $E_{\text {cell }}^{\circ}$ is negative, the cell reaction is non-spontaneous.