Chapter SH, Problem 18.6APP

To determine

To calculate: The oxidation number of chromium in the dichromate ion.

Answer to Problem 18.6APP

The oxidation number of chromium in ${\text{(Cr}}_2{\text{O}}_7{}^{2-})$ is $6+$ .

Explanation of Solution

Given data:

The symbol for dichromate ion: ${\text{(Cr}}_2{\text{O}}_7{}^{2-})$ .

The oxidation number of dichromate ion is $2-$ .

The oxidation number of oxygen is $2-$ .

As per the problem,

Let the oxidation number of chromium be $x+$ .

There are two chromium atoms in dichromate ion.

The oxidation number of dichromate ion is $2-$ .

The oxidation number of oxygen is $2-$ .

There are seven oxygen atoms in the ${\text{(Cr}}_2{\text{O}}_7{}^{2-})$ .

Therefore, the oxidation number of dichromate ion can be written as

  $\begin{array}{l}(x+\times 2)+(7\times 2-)=2-\\ 2x+=(2-)-(14-)\\ 2x=12+\\ x=6+\end{array}$

Conclusion:

The oxidation number of chromium in ${\text{(Cr}}_2{\text{O}}_7{}^{2-})$ is $6+$