Identify the correct sequence of increasing number of `pi`-bonds in the structure of the following molecules:
(I)`H_(2)S_(2)O_(6)` (II)`H_(2)S_(2)O_(3)` (III)`H_(2)S_(2)S_(5)`

Options

A. I, II and III
B. II, I and III
C. II, III and I
D. I, III and II

Explanation

To determine the correct sequence of increasing number of pi-bonds in the structures of the given molecules, we will analyze each molecule step by step.

### Step 1: Analyze the structure of H₂S₂O₆
- **Structure**: H₂S₂O₆ has two sulfur atoms and six oxygen atoms. The structure can be represented as:
- S-S bond (single bond)
- Each sulfur is bonded to three oxygen atoms, where two of the oxygen atoms are bonded via double bonds (S=O) and one via a single bond (S-O).
- **Pi-bonds**: In this structure, there are 2 double bonds (S=O), contributing 2 pi-bonds.

### Step 2: Analyze the structure of H₂S₂O₃
- **Structure**: H₂S₂O₃ has two sulfur atoms and three oxygen atoms. The structure can be represented as:
- S-S bond (single bond)
- Each sulfur is bonded to one oxygen via a double bond (S=O) and one oxygen via a single bond (S-O).
- **Pi-bonds**: In this structure, there is 1 double bond (S=O), contributing 1 pi-bond.

### Step 3: Analyze the structure of H₂S₂O₅
- **Structure**: H₂S₂O₅ has two sulfur atoms and five oxygen atoms. The structure can be represented as:
- S-S bond (single bond)
- Each sulfur is bonded to two oxygen atoms via double bonds (S=O) and one oxygen via a single bond (S-O).
- **Pi-bonds**: In this structure, there are 2 double bonds (S=O), contributing 2 pi-bonds.

### Step 4: Count the total number of pi-bonds
- **H₂S₂O₆**: 2 pi-bonds
- **H₂S₂O₃**: 1 pi-bond
- **H₂S₂O₅**: 2 pi-bonds

### Step 5: Arrange in increasing order
- H₂S₂O₃ (1 pi-bond) < H₂S₂O₆ (2 pi-bonds) = H₂S₂O₅ (2 pi-bonds)

Since H₂S₂O₆ and H₂S₂O₅ both have the same number of pi-bonds, we can list them together.

### Final Sequence
The correct sequence of increasing number of pi-bonds is:
1. H₂S₂O₃ (1 pi-bond)
2. H₂S₂O₆ and H₂S₂O₅ (2 pi-bonds)