Chapter 19.2, Problem 26SSC

Interpretation Introduction

Interpretation:

The relationship between change in oxidation number and electron transferred is to be explained.

The relationship between change in oxidation number and oxidation-reduction is to be explained.

Concept introduction:

Oxidation number: It is defined as charge the atom would have if electrons are not shared but transfer completely.

Answer to Problem 26SSC

When an atom is oxidized, it loses its electrons and its oxidation number is increased.

When an atom is reduced, it accepts some electrons and its oxidation number is reduced.

Number of electrons lost = increase in oxidation number

Number of electrons gained = decrease in oxidation number

Explanation of Solution

Consider the following redox reaction:

$Zn+C{u}^{+2}\to Z{n}^{+2}+Cu$

Oxidation number are as:

$\stackrel{0}{Zn}+\stackrel{+2}{C{u}^{+2}}\to \stackrel{+2}{Z{n}^{+2}}+\stackrel{0}{Cu}$

Increase in oxidation number of $Zn=+2$

It means it loses 2 electrons to get oxidized.

Decrease in oxidation number of $C{u}^{+2}=-2$

It means it gains 2 electrons to get reduced.

Conclusion

When an atom is oxidized, it loses its electrons and its oxidation number is increased.

When an atom is reduced, it accepts some electrons and its oxidation number is reduced.