A : Acetate ion is less basic than the methoxide ion.
R : The acetate ion is resonance stabilized.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question regarding the basicity of acetate ion compared to methoxide ion, we can break it down into several steps:

### Step 1: Understand the Assertion
The assertion states that "acetate ion is less basic than the methoxide ion." To evaluate this, we need to define what basicity means in this context. Basicity refers to the ability of a species to donate a lone pair of electrons or accept a proton (H+).

### Step 2: Analyze the Acetate Ion
The acetate ion (CH3COO-) has a structure where the negative charge on the oxygen is delocalized due to resonance. This means that the negative charge can be spread out over multiple atoms, which stabilizes the ion. The resonance structures can be represented as follows:
- CH3C(=O)O^− ↔ CH2=C(OH)O^−

Due to this delocalization, the acetate ion is resonance stabilized, which reduces its tendency to donate its lone pair or accept a proton. Thus, it is less basic.

### Step 3: Analyze the Methoxide Ion
The methoxide ion (CH3O-) has a negative charge localized on the oxygen atom. The presence of the methyl group (CH3) exerts a +I (inductive) effect, which increases the electron density on the oxygen. This makes the methoxide ion more likely to donate its lone pair or accept a proton, thus making it more basic than the acetate ion.

### Step 4: Compare Basicity
From the analysis:
- Acetate ion is less basic due to resonance stabilization.
- Methoxide ion is more basic due to the localized negative charge and the electron-donating effect of the methyl group.

### Step 5: Conclusion
Both the assertion and the reason are true:
- Assertion: Acetate ion is less basic than methoxide ion (True).
- Reason: The acetate ion is resonance stabilized (True).

Since the reason explains why the assertion is true, the correct option is that both the assertion and reason are true, and the reason is the correct explanation of the assertion.

### Final Answer
The correct option is **Option 1**: Both assertion and reason are true, and the reason is the correct explanation of the assertion.

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