Question

Assertion: HI cannot be prepared by the reaction of KI with concentrated $H_{2}S{O}_4$.
Reason: HI has lowest H-X bond strength among halogen acids.

• A. Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion
• B. Both assertion and reason are wrong statements.
• C. Assertion is wrong but reason is correct statement.
• D. Assertion is correct but reason is wrong statement.
• E. Both assertion and reason are correct statements, and reason is the correct explanation of the assertion

Answer 1

The correct option is A Both assertion and reason are correct statements, but reason is not the correct explanation of the assertion

Analysing the assertion

HI cannot be prepared by the reaction of KI with concentrated $H_{2}S{O}_4$.
When KI reacts with sulphuric acid $H_{2}S{O}_4$, following reaction takes place:

$2KI+H_{2}S{O}_4\to 2KHS{O}_4+2HI$

But, $H_{2}S{O}_4$ is a strong oxidising agent that readily oxidised HI(produced in the reaction) to $I_2$.

$2HI+H_{2}S{O}_4\to I_2+S{O}_2+H_{2}O$

Thus, HI cannot be prepared by the reaction of KI with concentrated $H_{2}S{O}_4$.

So, the assertion is correct.

Analysing the Reason

HI has the lowest H – X bond strength among halogen acids. As we go down the group the size of halogen increases and Iodine has the largest size.
This results in poor overlapping of Iodine’s orbitals with 1s orbital of hydrogen, due to which bond strength decreases.
Thus, HI has lowest H – X bond strength among halogen acids.
So, the reason is also correct.

Hence, assertion and reason both are correct but both statements are independent, and reason is not the correct explanation of assertion.

Hence, option (B) is correct.