A compound which liberates reddish brown gas around the anode during electrolysis in its molten state is :

Options

A. sodium chloride
B. Copper (II) oxide
C. Copper (II) sulphate
D. Lead (II) bromide

Explanation

To solve the question, "A compound which liberates reddish brown gas around the anode during electrolysis in its molten state is:", we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electrolysis**:
- Electrolysis involves the decomposition of a compound in its molten state or in solution by passing an electric current through it. The process occurs in an electrolytic cell that consists of two electrodes: an anode (positive) and a cathode (negative).

2. **Identifying the Anode Reaction**:
- At the anode, oxidation reactions occur. This means that negatively charged ions (anions) migrate towards the anode and lose electrons.

3. **Analyzing Possible Compounds**:
- We need to identify compounds that can liberate a reddish-brown gas at the anode. Common compounds include sodium chloride (NaCl), copper(II) oxide (CuO), copper(II) sulfate (CuSO4), and lead(II) bromide (PbBr2).

4. **Determining the Anions**:
- For each of these compounds, we can identify the anions:
- Sodium chloride (NaCl) → Cl⁻ (chloride ion)
- Copper(II) oxide (CuO) → O²⁻ (oxide ion)
- Copper(II) sulfate (CuSO4) → SO₄²⁻ (sulfate ion)
- Lead(II) bromide (PbBr2) → Br⁻ (bromide ion)

5. **Identifying the Reddish-Brown Gas**:
- Among these anions, we need to determine which one produces a reddish-brown gas when oxidized at the anode:
- Chloride ions (Cl⁻) produce chlorine gas (Cl₂), which is colorless.
- Oxide ions (O²⁻) produce oxygen gas (O₂), which is also colorless.
- Sulfate ions (SO₄²⁻) do not produce a gas that is reddish-brown.
- Bromide ions (Br⁻) produce bromine gas (Br₂), which is reddish-brown.

6. **Conclusion**:
- The only compound that liberates a reddish-brown gas (bromine) at the anode during electrolysis is lead(II) bromide (PbBr2).

### Final Answer:
The compound which liberates reddish-brown gas around the anode during electrolysis in its molten state is **Lead(II) bromide (PbBr2)**.