Assertion:- `pKa_(1)` of fumeric acid is greater than maleic acid.
Reason Conjugate base of fumeric acid is more stable due to intramolecular H-bonding.

Options

A. If both Assertion `&` Reason are True `&` the Reason is a correct explanation of the Assertion.
B. If both Assertion `&` Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion `&` Reason are False.

Answer

To solve the assertion-reason question regarding fumaric acid and maleic acid, we will analyze both the assertion and the reason step by step.

### Step 1: Understand the Assertion
The assertion states that the pKa1 of fumaric acid is greater than that of maleic acid.

- **Fumaric Acid Structure**: Fumaric acid has a trans configuration with the formula HOOC-CH=CH-COOH.
- **Maleic Acid Structure**: Maleic acid has a cis configuration with the formula HOOC-CH=CH-COOH.

### Step 2: Analyze the pKa Values
pKa is inversely related to the acidity constant (Ka). A higher pKa value indicates a weaker acid.

- **Maleic Acid**: When maleic acid loses a proton (H+), its conjugate base is stabilized by intramolecular hydrogen bonding due to its cis configuration. This stabilization increases the acidity (higher Ka) and thus lowers the pKa.

- **Fumaric Acid**: When fumaric acid loses a proton, its conjugate base does not benefit from intramolecular hydrogen bonding due to its trans configuration. This means that the conjugate base is less stable, resulting in a lower Ka and a higher pKa.

### Step 3: Conclusion on the Assertion
Since the pKa of fumaric acid is indeed greater than that of maleic acid, the assertion is **true**.

### Step 4: Understand the Reason
The reason states that the conjugate base of fumaric acid is more stable due to intramolecular hydrogen bonding.

- This statement is **false** because the conjugate base of fumaric acid does not have intramolecular hydrogen bonding. Instead, it is the conjugate base of maleic acid that is stabilized by such bonding.

### Step 5: Conclusion on the Reason
The reason provided is incorrect, as the stability of the conjugate base of fumaric acid is not due to intramolecular hydrogen bonding.

### Final Answer
- **Assertion**: True (pKa1 of fumaric acid is greater than that of maleic acid)
- **Reason**: False (the conjugate base of fumaric acid is not stabilized by intramolecular hydrogen bonding)

Thus, the correct answer is that the assertion is true, and the reason is false.