(A): HBr is stronger acid than HI.
(R) : Bromine is more electronegative than iodine.

Options

A. Both A & R are true, R is the correct explanation of A
B. Both A & R are true, R is not correct explanation of A
C. A is true, R is false
D. A is false, R is true

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion (A)**:
- The assertion states that HBr is a stronger acid than HI.
- To evaluate this, we need to consider the bond strength between hydrogen and the halogens (bromine and iodine).

2. **Analyzing the Bond Strength**:
- HBr has a bond between hydrogen (H) and bromine (Br), while HI has a bond between hydrogen (H) and iodine (I).
- The bond strength generally decreases as we move down the group in the periodic table due to the increasing size of the halogen atoms.

3. **Comparing HBr and HI**:
- Bromine (Br) has a principal quantum number of 4, and iodine (I) has a principal quantum number of 5.
- As the size of iodine is larger than that of bromine, the bond length in HI is longer than in HBr, leading to weaker bond strength in HI compared to HBr.

4. **Conclusion on Assertion**:
- Since HI has a weaker bond than HBr, HI will dissociate more easily in solution, making it a stronger acid than HBr.
- Therefore, the assertion that HBr is stronger than HI is **false**.

5. **Understanding the Reason (R)**:
- The reason states that bromine is more electronegative than iodine.
- Electronegativity generally decreases as we move down a group in the periodic table. Thus, bromine (Br) is indeed more electronegative than iodine (I).

6. **Conclusion on Reason**:
- The reason given is **true**.

### Final Assessment:
- Assertion (A) is **false**.
- Reason (R) is **true**.

Thus, the correct conclusion is that the assertion is false while the reason is true.