Chapter 23, Problem 19E

Interpretation Introduction

Interpretation:

A plausible graph of ${\Delta }_r{G}^0$ as a function of temperature for the reaction of $2{\text{Ca(s)+O}}_2(g)\to 2CaO(s)$ should be sketched.

Concept introduction:

In the graph of ${\Delta }_r{G}^0$ as a function of temperature, the dependent variable is ${\Delta }_r{G}^0$.

As a competition between Mg and Ca for O atoms, Mg has O initially in MgO, and Ca acquires them in forming CaO. This is represented by the following reactions.

$\begin{array}{l}2{\text{Ca(s)+O}}_2(g)\to \text{2CaO(s)}\\ \text{2MgO(s) }\to 2{\text{Mg(s) +O}}_2(g)\end{array}$