Chapter 19, Problem 78A

Interpretation Introduction

Interpretation:

The oxidation number of chromium in given compounds is to be determined.

Concept introduction:

Copper is a transition metal. All the transition metals show color in their compounds.

Yellow color compound of chromium is $K_{2}Cr{O}_4$

Red color compound of chromium is $K_{2}C{r}_2{O}_7$

Answer to Problem 78A

Oxidation number of $Cr$ in $K_{2}Cr{O}_4$ = +6

Oxidation number of $Cr$ in $K_{2}C{r}_2{O}_7$ = +6

Explanation of Solution

Oxidation number of $Cr$ in $K_{2}Cr{O}_4$

$\begin{array}{l}2\times 1+x+(-2\times 4)=0\\ 2+x-8=0\\ x=6\end{array}$

Oxidation number of $Cr$ in $K_{2}C{r}_2{O}_7$

$\begin{array}{l}2\times 1+2\times x+(-2\times 7)=0\\ 2+2x-14=0\\ 2x=12\\ x=6\end{array}$

Conclusion

Thus,

Oxidation number of $Cr$ in $K_{2}Cr{O}_4$ (yellow colored compound) = +6

Oxidation number of $Cr$ in $K_{2}C{r}_2{O}_7$ (red colored compound) = +6