Question

Assertion :Lithium salts are mostly hydrated. Reason: The hydration enthalpies of alkali metal ions decrease with increase in ionic sizes.

• 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. Assertion is correct but Reason is incorrect
• D. Both Assertion and Reason are incorrect

Answer 1

The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion

• Lithium is the smallest in size among the alkali metals. Hence, $L{i}^{+}$ ion can polarize water molecules more easily than other alkali metals. As a result, water molecules get attached to lithium salts as water of crystallization.
• Hence, lithium salts such as trihydrated lithium chloride $\left(LiC1.3H20\right)$ are commonly hydrated. As the size of the ions increases, their polarizing power decreases. Thus hydration enthalpies decreases.Hence, other alkali metal ions usually form anhydrous salts.
  
• Hence both Assertion and Reason are correct also Reason is correct explanation for Assertion.