Identify the compounds A and B in the following reaction sequence.
`CaC_2(s)+ H_2O(l) to A(g) underset(HgSO_4)overset(H_2SO_4)to B (l)`

Options

A. A is ethylene, B is acetaldehyde
B. A is acetylene, B is propionaldehyde
C. A is ethane, B is ethanol
D. A is acetylene, B is acetaldehyde.

Answer

To identify the compounds A and B in the given reaction sequence, we can break down the reactions step by step.

### Step 1: Identify Compound A
1. **Starting Material**: The reaction begins with Calcium Carbide (CaC₂) and water (H₂O).
2. **Reaction with Water**: When Calcium Carbide reacts with water, it produces Calcium Hydroxide (Ca(OH)₂) and Acetylene (C₂H₂).
- **Chemical Reaction**:
\[ \text{CaC}_2(s) + 2 \text{H}_2\text{O}(l) \rightarrow \text{Ca(OH)}_2(aq) + \text{C}_2\text{H}_2(g) \]
3. **Identify Compound A**: From the above reaction, Acetylene (C₂H₂) is produced as a gas.
- **Compound A**: C₂H₂ (Acetylene)

### Step 2: Identify Compound B
1. **Second Reaction**: The Acetylene (C₂H₂) then undergoes a reaction in the presence of Mercury(II) Sulfate (HgSO₄) and Sulfuric Acid (H₂SO₄).
2. **Hydration of Acetylene**: This reaction is known as the hydration of Acetylene, which leads to the formation of Acetaldehyde (CH₃CHO).
- **Chemical Reaction**:
\[ \text{C}_2\text{H}_2(g) + \text{H}_2\text{O} \xrightarrow{\text{HgSO}_4, \text{H}_2\text{SO}_4} \text{CH}_3\text{CHO}(l) \]
3. **Identify Compound B**: The product formed from this reaction is Acetaldehyde (CH₃CHO).
- **Compound B**: CH₃CHO (Acetaldehyde)

### Conclusion
- **Compound A**: C₂H₂ (Acetylene)
- **Compound B**: CH₃CHO (Acetaldehyde)

### Final Answer
- A = Acetylene (C₂H₂)
- B = Acetaldehyde (CH₃CHO)

---