Chapter 19, Problem 80A

Interpretation Introduction

Interpretation:

The structure of aluminum oxide is to be drawn and the replacement reaction between chromium and aluminum ion is to be shown.

Concept introduction:

The replacement of one of the elements of a compound by another element is called displacement reaction. It will become a redox reaction if the oxidation states of the exchanging elements are different.

Answer to Problem 80A

Structure of aluminum oxide:

Reaction of aluminum replacement by chromium (III) ion:

$A{l}_2{O}_3+2C{r}^{3+}\to 2A{l}^{3+}+C{r}_2{O}_3$

The above reaction is not a redox reaction.

Explanation of Solution

In the above structure of aluminum oxide, the oxidation states of aluminum and oxygen are +3 and -2 respectively which cancel each other out and make the compound electrically stable. In the displacement reaction, the oxidation states of ions are unchanged, hence it is not a redox reaction because neither oxidation nor reduction is taking place.