Chapter 18, Problem 1STP

Interpretation Introduction

Interpretation: The oxidized and reduced elements are to be identified in the given reaction.

Concept introduction: The change in oxidation state explains the loss and gain of electrons in oxidation−reduction reactions.

Answer to Problem 1STP

1. Calcium is oxidized and oxygen is reduced.

Explanation of Solution

A. Loss of electrons by ion, molecules or atoms is termed as oxidation and gain of electrons by ion, molecules or atoms is termed as reduction. The given traction is as follows:

$2\text{Ca}\left(s\right)+{\text{O}}_2\left(g\right)\to 2\text{CaO}\left(s\right)$

In this equation, calcium is oxidize because oxidation of calcium increases from 0 to +2 and oxygen is reduced because oxidation state of oxygen decreases from 0 to -2. Thus correct option is A.

Conclusion

B. Oxygen is oxidized and calcium is reduced.

In given reaction, oxidation state of calcium increases and oxidation state of oxygen decreases thus, oxygen is reduced and calcium is oxidized.

C. One of the oxygen atoms of oxidized, and the other oxygen atom is oxidized.

In given reaction, oxidation state of calcium increases and oxidation state of oxygen decreases. Thus, oxidation state of both oxygen atoms decreases from 0 to -2.

D. The reduction above is not an oxidation-reduction reaction.

Above reaction is oxidation-reduction reaction because one of the reactant is oxidized and other is reduced.