Given below are two statements: One is labelled as Assertion A and the other is labelled as Reason R:
Assertion A: H₂ Te is more acidic than H₂ S.
Reason R: Bond dissociation enthalpy of H₂ Te is lower than H₂ S.
In the light of the above statements, choose the most appropriate from the options given below:

Solution

Chemistry ma’am · 4 steps

Going down group 16, the H–E bond gets weaker, so H⁺ leaves more easily and acidity rises.

1. Bond strength trend. From S to Te the atom gets much larger, so its overlap with the small H 1s orbital gets poorer. The H–E bond becomes longer and weaker.

   Hydride	H–E bond enthalpy	Acid strength
   H₂O	463 kJ mol⁻¹	weakest
   H₂S	347 kJ mol⁻¹	weaker
   H₂Se	276 kJ mol⁻¹	stronger
   H₂Te	238 kJ mol⁻¹	strongest

2. Check both statements. R is true because the H–Te bond is weaker than the H–S bond. A is true because H₂Te gives up H⁺ more easily than H₂S.
3. Link them. Releasing H⁺ means breaking the H–E bond, so a weaker bond means a stronger acid. The low bond dissociation enthalpy is exactly why H₂Te is more acidic.
4. So. Both A and R are true, and R correctly explains A. The answer is (a).

The idea to keep. For hydrides down a group, bond strength decides acidity, not electronegativity. A bigger central atom gives a weaker H–E bond, so it is easier to release H⁺ and the acid is stronger.

Answer from the NTA final answer key. Solution by PrepWiser.