Sodium salt of the following acid which is needed for the preparation of methane:

Options

A. Ethanoic acid
B. Propanoic acid
C. Butanoic acid
D. Pentanoic acid

Explanation

To determine the sodium salt of the acid needed for the preparation of methane, we can follow these steps:

### Step 1: Identify the Acid
The acid we need is ethanoic acid (acetic acid), which has the chemical formula CH₃COOH.

### Step 2: Formation of Sodium Salt
When ethanoic acid reacts with sodium hydroxide (NaOH), it forms sodium ethanoate (sodium acetate). The reaction can be represented as:
\[ \text{CH}_3\text{COOH} + \text{NaOH} \rightarrow \text{CH}_3\text{COONa} + \text{H}_2\text{O} \]
Here, the hydrogen from the carboxylic group (-COOH) is replaced by sodium (Na⁺), resulting in the formation of sodium ethanoate (CH₃COONa).

### Step 3: Decarboxylation Process
To produce methane (CH₄) from sodium ethanoate, we need to perform a decarboxylation reaction. This is typically done by heating sodium ethanoate with calcium oxide (CaO):
\[ \text{CH}_3\text{COONa} + \text{CaO} \xrightarrow{\text{heat}} \text{CH}_4 + \text{Na}_2\text{CO}_3 \]
In this reaction, the sodium salt loses a carbon dioxide molecule (CO₂) and forms methane.

### Step 4: Conclusion
Thus, the sodium salt of ethanoic acid (sodium ethanoate) is needed for the preparation of methane.

### Final Answer
The sodium salt of the acid needed for the preparation of methane is **sodium ethanoate (CH₃COONa)**.

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