Question

In which of the following sulphur is present in +5 oxidation state?

• A. Dithionic acid
• B. Sulphurous acid
• C. Sulphuric acid
• D. Disulphuric acid

Answer 1

The correct option is A Dithionic acid

Sulphurus acid is $H_{2}S{O}_3$, Oxidation state of Sulphur is +6.

Sulphuric acid is $H_{2}S{O}_4$, Oxidation state of Sulphur is +8.

$HO-\underset{\underset{\text{O}}{||}}{\stackrel{\underset{||}{\text{O}}}{S}}-OH$

Dithionic acid($H_2{S}_2{O}_6$),In which the sulphur is present in +5 oxidation state

$HO-\underset{\underset{\text{O}}{||}}{\stackrel{\underset{||}{\text{O}}}{S}}-\underset{\underset{\text{O}}{||}}{\stackrel{\underset{||}{\text{O}}}{S}}-OH$

Assume oxidation state of sulphur is $x$,

So, $2(+1)+2\left(x\right)+6(-2)=0$

$2+2x-12=0$

$x=+5$.

The structure of Disulphuric acid is given below:

$HO-\underset{\underset{\text{O}}{||}}{\stackrel{\underset{||}{\text{O}}}{S}}-O-\underset{\underset{\text{O}}{||}}{\stackrel{\underset{||}{\text{O}}}{S}}-OH$

Assume oxidation state of sulphur is $x$,

So, $2(+1)+2\left(x\right)+7(-2)=0$

$2+2x-14=0$

$x=+6$.

Hence option A is correct.