Assertion : Sn in +2 oxidation state is a reducing agent while Pb in + 4 state is an oxidising agent.
Reason : Inert pair effect is due to participation of s electrons in bond formation.

Explanation

To analyze the assertion and reason provided in the question, we can break it down step by step.

### Step 1: Understanding the Assertion
The assertion states that Sn in the +2 oxidation state acts as a reducing agent while Pb in the +4 oxidation state acts as an oxidizing agent.

- **Explanation**:
- A reducing agent is a substance that donates electrons to another substance and is oxidized in the process.
- Sn in the +2 state can be oxidized to Sn in the +4 state, meaning it can lose electrons and thus act as a reducing agent.
- Pb in the +4 state can gain electrons to be reduced to Pb in the +2 state, meaning it can accept electrons and thus acts as an oxidizing agent.

### Step 2: Understanding the Reason
The reason states that the inert pair effect is due to the participation of s electrons in bond formation.

- **Explanation**:
- The inert pair effect refers to the tendency of the s electrons (in the outermost shell) to remain non-bonding or "inert" as we move down the group in the periodic table.
- This effect is actually due to the non-participation of s electrons in bond formation, not their participation. Thus, the reason provided is incorrect.

### Step 3: Conclusion
- The assertion is true because Sn in +2 state is indeed a reducing agent and Pb in +4 state is an oxidizing agent.
- The reason is false because it incorrectly describes the inert pair effect as a participation of s electrons in bond formation.

### Final Answer
- **Assertion**: True
- **Reason**: False