Question

The oxidation number of oxygen in hydrogen peroxide is:

• A. 1
• B. -1
• C. 2
• D. -2

Answer 1

Answer: (B)

-1

Answer 2

Molecular formula of hydrogen peroxide is $H _{2} O _{2}$.
The oxidation number of $H$ is $+1$, but it is $-1$ in when combined with less electronegative elements.
Since oxygen is more electronegative than hydrogen, therefore oxidation no. of hydrogen in $H _{2} O _{2}$ will be $+1$.
Let the oxidation no. of oxygen in $H _{2} O _{2}$ be $x$.
As we know that, the sum of the oxidation numbers of all the atoms in a neutral compound is $0$ .
$\therefore( x \times 2)+((+1) \times 2)=0$
$\Rightarrow 2 x +2=0$
$\Rightarrow x =-1$
Hence, the oxidation no. of oxygen in hydrogen peroxide is $-1$.