Assertion : Weak acids have very strong conjugate bases while strong acids have weak conjugate bases.
Reason : Conjugate acid - base pair differ only by one proton.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Explanation

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

### Step 1: Analyze the Assertion
The assertion states: "Weak acids have very strong conjugate bases while strong acids have weak conjugate bases."

1. **Definition of Weak and Strong Acids**:
- Weak acids are those that do not completely dissociate in solution, meaning they only partially release H⁺ ions.
- Strong acids completely dissociate in solution, releasing all of their H⁺ ions.

2. **Conjugate Bases**:
- The conjugate base of an acid is what remains after the acid donates a proton (H⁺).
- For a weak acid, since it does not dissociate completely, its conjugate base is relatively strong because it can readily accept a proton back.
- For a strong acid, its conjugate base is weak because it has little tendency to accept a proton, as the acid has already fully dissociated.

**Conclusion**: The assertion is true because weak acids do indeed have strong conjugate bases, while strong acids have weak conjugate bases.

### Step 2: Analyze the Reason
The reason states: "Conjugate acid-base pairs differ only by one proton."

1. **Definition of Conjugate Acid-Base Pairs**:
- A conjugate acid-base pair consists of two species that can be transformed into one another by the gain or loss of a proton (H⁺).
- For instance, in the case of acetic acid (CH₃COOH) and its conjugate base (CH₃COO⁻), they differ by one proton.

2. **Examples**:
- For strong acids like HCl, the conjugate base is Cl⁻, and they differ by one proton (H⁺).
- For weak acids like acetic acid, the conjugate base is CH₃COO⁻, which also differs by one proton.

**Conclusion**: The reason is true because conjugate acid-base pairs do indeed differ by one proton.

### Final Conclusion
Both the assertion and the reason are true statements. However, the reason does not provide a correct explanation for the assertion. Therefore, the answer is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion.

### Answer:
**Option B: Both assertion and reason are true, but reason is not the correct explanation of assertion.**

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