Medium MCQ +4 / -1 PYQ · JEE Mains 2023

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R

Assertion A : Beryllium has less negative value of reduction potential compared to the other alkaline earth metals.

Reason R : Beryllium has large hydration energy due to small size of Be$^{2+}$ but relatively large value of atomization enthalpy

In the light of the above statements, choose the most appropriate answer from the options given below :

  1. A Both A and R are correct but R is NOT the correct explanation of A
  2. B Both A and R are correct and R is the correct explanation of A Correct answer
  3. C A is correct but R is not correct
  4. D A is not correct but R is correct

Solution

The most appropriate answer is Both A and R are correct and R is the correct explanation of A. <br/><br/> <b>Assertion A</b> states that beryllium has a less negative value of reduction potential compared to the other alkaline earth metals. This assertion is correct, as beryllium has higher ionization energy and a smaller atomic radius than the other alkaline earth metals, which makes it more difficult to reduce Be<sup>2+</sup> to Be metal. <br/><br/> <b>Reason R</b> provides an explanation for Assertion A. Beryllium has a relatively large value of atomization enthalpy due to the strong Be-Be bonds in the solid state, but it also has a large hydration energy due to the small size of Be<sup>2+</sup> ions. The strong Be-Be bonds make it difficult to reduce Be<sup>2+</sup> to Be metal, and the small size of Be<sup>2+</sup> ions leads to a large hydration energy. This makes it energetically unfavorable to remove the Be<sup>2+</sup> ion from the aqueous phase and reduce it to Be metal, which results in a less negative value of reduction potential for beryllium. <br/><br/> Therefore, both Assertion A and Reason R are correct, and Reason R provides the correct explanation for Assertion A.

About this question

Subject: Chemistry · Chapter: s-Block Elements · Topic: Alkali Metals

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