Question

Assertion: ${H_2}S$ is less acidic than ${H_2}Te$.
Reason: $Te$ has a larger radius than $S$.
A.Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B.Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C.The assertion is correct but the Reason is incorrect.
D.Both Assertion and Reason are incorrect.

Answer 1

This is one of the varieties of questions in which we have Assertion and the reason in the form of statements. First, we should understand the statements given in assertion and reason and check whether they are correct or incorrect. If both the Assertion and Reason are correct then we will relate the reason with the Assertion and check if the reason is a correct explanation of assertion.

Complete step by step answer:
First, we will check the Assertion and Reason one by one and check whether they are correct or incorrect.
We know that $S$ (Sulphur) and $Te$ (Tellurium) belong to the oxygen family. We know that down the group bond length increases which implies that bond length $H - Te$ is greater than $H - S$. It is very easy to break the larger bond because of its less stability compared to the shorter bond. So due to weak bonds, it will be easier to give hydrogen ions in $H - Te$ as compared to $H - S$. So the Assertion: ${H_2}S$ is less acidic than ${H_2}Te$ is correct.
We know that down the group size of the atom increases. In the oxygen family from $S$ to $Te$ size of the atom increases which implies that tellurium has a larger radius than Sulphur. So the Reason: $Te$ has a larger radius than $S$ is correct.
So, both Assertion and Reason are correct but the reason is not the correct explanation of assertion.

Therefore, the correct option is (B).

Note:
On moving down the group the size of the atom increases and ionization enthalpy decreases. This results in dissociating the bond easily.If bond dissociation is less, acidity is less. Bond dissociation is directly proportional to acidity.