Chapter 20, Problem 3STP

Interpretation Introduction

Interpretation:

The standard potential is to be calculated.

Concept introduction:

Reduction will occur at that electrode having high reduction potential.

Answer to Problem 3STP

Correct answer:

Option B - $\text{3}\text{.172}\text{V}$

Explanation of Solution

Reason for correct option:

The reduction potential of ${\text{Ag}}^{\text{+1}}$ electrode is more than that of ${\text{Mg}}^{\text{2+}}|\text{Mg}$. So, reduction will occur at the silver electrode and oxidation will occur at the magnesium electrode and the cell reaction will be given as

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

The reduction potential of ${\text{Mg}}^{\text{+2}}|\text{Mg}\text{=-}\left(\text{-2}\text{.372}\right)$ V

The reduction potential of ${\text{Ag}}^{\text{+1}}|\text{Ag}\text{=}\left(\text{0}\text{.7996}\right)$ V

$\begin{array}{l}{\text{E°}}_{\text{cell}}{\text{=E°}}_{\left(\text{cathode}\right)}{\text{-E°}}_{\left(\text{anode}\right)}\\ \text{=0}\text{.7996-}\left(\text{-2}\text{.372}\right)\\ \text{=3}\text{.172}\text{V}\end{array}$

The standard potential of a cell is $\text{3}\text{.172}\text{V}$

Conclusion

Reasons for incorrect options:

A. Not math with calculated value.

C. Not math with calculated value.

D. Not math with calculated value.