Chapter 20.3, Problem 27SSC

Interpretation Introduction

Interpretation:

Extraction of $\text{1}\text{kg}\text{Ag}$ from its ions requires less energy than extraction of $\text{1}\text{kg}\text{Al}$ from its ions by electrolysis is to be explained.

Concept introduction:

Electrochemistry is study of relation between electrical energy and chemical changes that takes place in redox reaction. There are three main aspects of electrochemistry branch, those are:

1. Electrolysis
2. Electrochemical cell
3. Electrolytic conduction.

Electrolysis is a process in which decomposition of electrolyte occurs on flow of electricity through its aqueous solution or molten state. The instrument employed to carry out electrolysis is electrolytic cell. Example of electrolytic cell is when a secondary battery is recharged.

Answer to Problem 27SSC

The standard reduction potential of $\text{Ag}$ and $\text{Al}$ is $\text{0}\text{.7996}\text{V}$ and $\text{-1}\text{.662}\text{V}$, respectively. So, $\text{Ag}$ which have positive cell potential will readily undergo reduction as compared to $\text{Al}$ metal, hence, higher external voltage is required in case of $\text{Al}$ for electrolysis to occur.

Therefore, extraction of $\text{1}\text{kg}\text{Ag}$ from its ions requires less energy than extraction of $\text{1}\text{kg}\text{Al}$ from its ions by electrolysis.

Explanation of Solution

In electrolysis external voltage is applied which reverses the movement of electron in cell, so it drives non-spontaneous reaction.

The standard reduction potential of $\text{Ag}$ and $\text{Al}$ is $\text{0}\text{.7996}\text{V}$ and $\text{-1}\text{.662}\text{V}$, respectively. As per the latest convention of sign, the electrode at which reduction occurs with respect to standard hydrogen electrode is assigned positive sign or has higher reduction potential and the electrode at which oxidation occurs with respect to standard hydrogen electrode is assigned negative sign or has lower reduction potential.

So, $\text{Ag}$ which have positive cell potential will readily undergo reduction as compared to $\text{Al}$ metal, hence, higher external voltage is required in case of $\text{Al}$ for electrolysis to occur.

Conclusion

The standard reduction potential of $\text{Ag}$ and $\text{Al}$ is $\text{0}\text{.7996}\text{V}$ and $\text{-1}\text{.662}\text{V}$, respectively. So, $\text{Ag}$ which have positive cell potential will readily undergo reduction as compared to $\text{Al}$ metal, hence, higher external voltage is required in case of $\text{Al}$ for electrolysis to occur.

Therefore, extraction of $\text{1}\text{kg}\text{Ag}$ from its ions requires less energy than extraction of $\text{1}\text{kg}\text{Al}$ from its ions by electrolysis.