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Sum of \(\pi\)-bonds present in peroxodisulphuric acid and pyrosulphuric acid is___________

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Count π-bonds in double bonds (C=O, S=O, etc.) while analyzing structures of acids.

Updated On: Mar 31, 2026
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Correct Answer: 8

Solution and Explanation

To solve the problem of finding the total number of \(\pi\)-bonds in peroxodisulphuric acid and pyrosulphuric acid, let's analyze the structure of each compound:

1. Peroxodisulphuric acid (\(H_2S_2O_8\)):

In peroxodisulphuric acid, the structure involves two sulfate (\(SO_4^{-}\)) groups linked by a peroxide bond (\(O-O\)). Each sulfur atom is bonded to four oxygen atoms: one via a single (\(O-H\)), two via double bonds (\(S=O\)), and one via an \(O-O\) linkage or \(O-S\). Therefore, each sulfur has two \(\pi\)-bonds from the \(S=O\) double bonds.

Total \(\pi\)-bonds in peroxodisulphuric acid: \(4\) (2 from each sulfate group).

2. Pyrosulphuric acid (\(H_2S_2O_7\)):

In pyrosulphuric acid, the structure comprises two sulfate (\(SO_4^{-}\)) units sharing an oxygen atom (resembling two sulfuric acid units minus one water molecule). Each sulfur atom is bonded to four oxygen atoms: one with a hydroxyl group (\(O-H\)) and three others (\(S=O\)) joined via an oxygen (\(O\)-linkage).

Each sulfur atom in pyrosulphuric acid contains two \(\pi\)-bonds due to the \(S=O\) linkages.

Total \(\pi\)-bonds in pyrosulphuric acid: \(4\) (2 per sulfur within \((SO_4^{-})\) units, shared oxygen does not contribute additional \(\pi\)-bonds).

Thus, the total number of \(\pi\)-bonds in both acids is:
\(4\: (\text{from}\: H_2S_2O_8)\: +\: 4\: (\text{from}\: H_2S_2O_7)\: =\: 8\).

The sum of \(\pi\)-bonds is \(8\), fitting the expected range of 8 to 8.

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