Question

Given below are two statements : one is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A) : Lithium salts are hydrated.
Reason (R) : Lithium has higher polarising power than other alkali metal group members.
In the light of the above statements, choose the most appropriate answer from the options given below :

• A. Both (A) and (R) are correct and (R) is the correct explanation of (A).
• B. Both (A) and (R) are correct but (R) is NOT the correct explanation of (A).
• C. (A) is correct but (R) is not correct.
• D. (A) is not correct but (R) is correct.

Hint:

The degree of hydration of alkali metal ions decreases in the order: \( \text{Li}^+>\text{Na}^+>\text{K}^+>\text{Rb}^+>\text{Cs}^+ \). Small ions attract water more strongly!

Answer 1

The Correct Option is A

The given question involves assessing the correctness of two statements and understanding their relationship. Let's evaluate both the Assertion (A) and the Reason (R) to see how they connect:

1. Assertion (A): Lithium salts are hydrated.
   

   This statement is correct. Lithium salts, such as Lithium Chloride (LiCl), are known to form hydrates. This behavior is different from other alkali metal salts, which generally do not form hydrates.

2. Reason (R): Lithium has higher polarising power than other alkali metal group members.
   

   This statement is also correct. Lithium has a small ionic size and high charge density, which gives it a high polarising power. This allows lithium to distort electron clouds of the anions it interacts with more effectively than other alkali metals. This high polarising power leads to covalent character in lithium salts, making them more likely to interact with water molecules and form hydrates.

Now, let's analyze the connection between (A) and (R):

• Lithium’s high polarising power explains its unique ability among alkali metals to form hydrates, confirming that (R) is indeed the correct explanation for (A).

Conclusion: Both the Assertion (A) and the Reason (R) are correct, and the Reason (R) correctly explains the Assertion (A). Therefore, the most appropriate answer is:

Both (A) and (R) are correct and (R) is the correct explanation of (A).