Question

Calculate the oxidation number of the underlined elements in the following compounds.
a. $K\underset{–}{Mn}{O}_4$ b. $\underset{–}{Cr}{O}_2{Cl}_2$ c. $Na\underset{–}{I}{O}_3$

• A. a. $+7$ b. $+6$ c. $+5$
• B. a. $+9$ b. $+6$ c. $+5$
• C. a. $+7$ b. $0$ c. $+5$
• D. None of these

Answer 1

The correct option is A a. $+7$ b. $+6$ c. $+5$

a) Let $x$ be the oxidation number of Mn in potassium permanganate $KMn{O}_4$.
Since, the overall charge on the complex is $0$, the sum of oxidation states of all elements in it should be equal to $0$.
$+1+x+4(-2)=0$
$x=+7$
b) Let $x$ be the oxidation number of Cr in chromyl chloride $Cr{O}_{2}C{l}_2$.
$x+2(-2)+2(-1)=0$
$x=+6$
c) Let $x$ be the oxidation number of I in nitric acid $NaI{O}_3$.
$1+x+3(-2)=0$
$x=+5$