Chapter 20, Problem 2STP

Interpretation Introduction

Interpretation:

The correct standard cell notation of a voltaic cell out of the given representation is to be explained.

Concept introduction:

Reduction will occur at that electrode having high reduction potential.

Answer to Problem 2STP

Correct answer:

Option B - $\text{Mg}|{\text{Mg}}^{\text{+2}}\parallel {\text{H}}^{\text{+}}|{\text{H}}^{\text{+2}}$

Explanation of Solution

Reason for correct option:

The reduction potential of ${\text{H}}^{\text{+}}|{\text{H}}^{\text{2}}$ electrode is more than that of ${\text{Mg}}^{\text{2+}}|\text{Mg}$. So, reduction will occur at the hydrogen electrode and oxidation will occur at the magnesium electrode and the cell reaction will be given as

${\text{2H}}^{\text{+}}\left(\text{aq}\right)\text{+Mg}\left(\text{s}\right)\to {\text{H}}^{\text{2}}{\text{+Mg}}^{\text{+2}}$

Conclusion

Reasons for incorrect options:

A. The reduction potential of ${\text{Ag}}^{\text{+1}}$ ion is greater than that of ${\text{Al}}^{\text{+3}}$ ion. So, the cell representation is not correct.

C. The reduction potential of ${\text{H}}^{\text{+1}}$ ion is greater than that of ${\text{Pb}}^{\text{+2}}$ ion. So, the cell representation is not correct.

D. The reduction potential of ${\text{Pb}}^{\text{+2}}$ ion is greater than that of ${\text{Al}}^{\text{+3}}$ ion. So, the cell representation is not correct.