JEE Chemistry 2023 Question with Solution

Given: We need the sum of $\pi$-bonds present in peroxodisulphuric acid and pyrosulphuric acid.

Find: Total number of $\pi$-bonds in both acids.

Peroxodisulphuric acid has structure

$$H - O - S(=O)_2 - O - O - S(=O)_2 - O - H$$

Number of $\pi$-bonds = $4$, because there are two $S=O$ bonds in each $\text{SO}_3$ group.

Pyrosulphuric acid has structure

$$H - O - S(=O)_2 - O - S(=O)_2 - O - H$$

Number of $\pi$-bonds = $4$, because there are two $S=O$ bonds in each $\text{SO}_3$ group.

So,

$$4 + 4 = 8$$

Therefore, the total number of $\pi$-bonds is $8$.

Given: Count only $\pi$-bonds present in the structures.

Find: The sum for peroxodisulphuric acid and pyrosulphuric acid.

A double bond contributes one $\pi$-bond. The bonds $O-O$, $S-O$, and $O-H$ are single bonds, so they do not contribute any $\pi$-bond.

In peroxodisulphuric acid, the structure shows two terminal $S=O$ bonds on each sulphur atom, giving

$$2 + 2 = 4$$

$\pi$-bonds.

In pyrosulphuric acid, again each sulphur atom has two terminal $S=O$ bonds, giving

$$2 + 2 = 4$$

$\pi$-bonds.

Hence total $\pi$-bonds are

$$4 + 4 = 8$$

Therefore, the required numerical value is $8$.