What is X in the following sequence of reactions?
`Xunderset(-(1)/(2)H_(2))overset(Na)rarrYunderset(CaO)overset(NaOH)rarrCH_(4)`

Options

A. Methanoic acid
B. Ethanoic acid
C. Propane
D. Methane

Answer

To determine what X is in the sequence of reactions provided, we can analyze the reactions step by step.

### Step 1: Identify the reaction of X with sodium
The first part of the reaction states that X is treated with sodium and half a molecule of hydrogen (−(1/2)H₂). This suggests that X is likely a carboxylic acid because carboxylic acids can react with sodium to form sodium salts.

### Step 2: Consider possible candidates for X
We consider two carboxylic acids: methanoic acid (HCOOH) and ethanoic acid (CH₃COOH).

1. **Methanoic Acid (HCOOH)**:
- When methanoic acid reacts with sodium, it forms sodium methanoate (HCOONa) and releases hydrogen gas.

2. **Ethanoic Acid (CH₃COOH)**:
- When ethanoic acid reacts with sodium, it forms sodium ethanoate (CH₃COONa) and releases hydrogen gas.

### Step 3: Determine Y
After the first reaction, we denote the product as Y.
- For methanoic acid, Y would be sodium methanoate (HCOONa).
- For ethanoic acid, Y would be sodium ethanoate (CH₃COONa).

### Step 4: Analyze the second reaction
The next step involves treating Y with NaOH in the presence of CaO. This suggests a decarboxylation reaction, where a carboxyl group is removed, leading to the formation of methane (CH₄).

1. **From Sodium Methanoate (Y)**:
- If Y is sodium methanoate, the reaction would not yield methane.

2. **From Sodium Ethanoate (Y)**:
- If Y is sodium ethanoate, the reaction with NaOH and CaO would lead to the loss of CO₂ and the formation of methane (CH₄).

### Conclusion
Based on the analysis, the only candidate that fits all the criteria and leads to the formation of methane is ethanoic acid (CH₃COOH). Therefore, X is:

**X = Ethanoic Acid (CH₃COOH)**

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