Question

Select the options in which the elements given in the square bracket have the same oxidation number.

• A. $K\left[Mn\right]O_4$
• B. $\left[Mn\right]O_2$
• C. $[Mn{]}_2{O}_3$
• D. $[Mn{]}_2{O}_7$

Answer 1

Answer: (A), (D)

The correct options are
A

$K\left[Mn\right]O_4$

D

$[Mn{]}_2{O}_7$

Since the options given to us are all electrically neutral compounds the sum of oxidation number for all the elements should be equal to zero. Let's solve all the options to see which options have the same oxidation number. You need to know that the oxidation number for K and O is +1 and -2 respectively.

(1) $K\left[Mn\right]O_4$, let the oxidation number of Mn be $x$.

$+1+x+4\times (-2)=0$

$x=+7$

(2) $\left[Mn\right]O_2$, let the oxidation number of Mn be $x$.

$x+2\times (-2)=0$

$x=+4$

(3) $[Mn{]}_2{O}_3$, let the oxidation number of Mn be $x$.

$2\times x+3\times (-2)=0$

$x=+3$

(4) $[Mn{]}_2{O}_7$, let the oxidation number of Mn be $x$.

$2\times x+7\times (-2)=0$

$x=+7$

So from the given options the oxidation number of Mn in $K\left[Mn\right]O_4$ and $[Mn{]}_2{O}_7$ is same and is equal to +7.