Question

Given that the standard reduction potentials for $M^{+}/M$ and $N^{+}/N$ electrodes at $298K$ are $0.52V$ and $0.25V$ 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 $-0.27V$
• C. The standard $EMF$ of the cell is $0.77V$
• D. The standard $EMF$ of the cell is $-0.77V$
• E. The standard $EMF$ of the cell is $0.27V$

Answer 1

Answer: (B)

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

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

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

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