Equivalent weight = Molecular mass / n 
n is the number of the electrons 
a) In SO2 S has oxidation number + 4 ; S has o.n. = 0 
equivalent weight = 64 / 4 = 16....

**Equivalent Weight Calculation for the Oxidizing Agent in the Reaction SO2 + H2S → 3S + 2H2O**

To determine the equivalent weight of the oxidizing agent in the given reaction, we need to understand the concept of equivalent weight and its calculation. The equivalent weight is the mass of a substance that can either accept or provide one mole of electrons during a redox reaction.

**Definition of Equivalent Weight:**
The equivalent weight of a substance is the molar mass of the substance divided by the number of electrons transferred in the balanced redox equation.

**Balanced Equation:**
The given chemical equation is:
SO2 + H2S → 3S + 2H2O

**Step 1: Determine the Oxidizing Agent:**
In the given reaction, the oxidizing agent is the species that causes the oxidation of another species. In this case, SO2 acts as the oxidizing agent because it is reduced from an oxidation state of +4 to 0.

**Step 2: Identify the Redox Process:**
To identify the redox process, we need to analyze the change in oxidation states of the elements involved in the reaction.

- In SO2, sulfur is in the +4 oxidation state, and in 3S, sulfur is in the 0 oxidation state. Therefore, sulfur is reduced from +4 to 0, and SO2 acts as an oxidizing agent.
- In H2S, sulfur is in the -2 oxidation state, and in 2H2O, oxygen is in the -2 oxidation state. Therefore, sulfur is oxidized from -2 to 0, and H2S acts as a reducing agent.

**Step 3: Write Half-Reactions:**
To calculate the equivalent weight of the oxidizing agent, we need to write the half-reaction for the oxidation process.

- The oxidation half-reaction for SO2 can be written as: SO2 + 4H+ + 4e- → S + 2H2O

**Step 4: Determine the Number of Electrons Transferred:**
By comparing the oxidation states of sulfur in the reactant and product, we can determine the number of electrons transferred during the oxidation process.

- In SO2, sulfur has an oxidation state of +4, while in S, sulfur has an oxidation state of 0. Thus, 4 electrons are transferred during the oxidation.

**Step 5: Calculate the Equivalent Weight:**
The equivalent weight of the oxidizing agent can now be calculated by dividing the molar mass of the substance by the number of electrons transferred.

- The molar mass of SO2 is approximately 64 g/mol.
- The number of electrons transferred during oxidation is 4.

Therefore, the equivalent weight of the oxidizing agent (SO2) is 64 g/mol ÷ 4 = 16 g/equiv.

**Conclusion:**
The equivalent weight of the oxidizing agent (SO2) in the given reaction is calculated to be 16 g/equiv. This value represents the mass of SO2 required to accept or provide one mole of electrons during a redox reaction.