Question

Among the statements (A)-(D), the correct ones are : (a) Lithium has the highest hydration enthalpy among the alkali metals. (b) Lithium chloride is insoluble in pyridine. (c) Lithium cannot form ethynide upon its reaction with ethyne. (d) Both lithium and magnesium react slowly with $H_2O$ .

• A. (a), (b) and (d) only
• B. (b) and (c) only
• C. (a), (c) and (d) only
• D. (a) and (d) only

Answer 1

The Correct Option is C

To determine which statements are correct, let's analyze each of the provided statements:

1. (a) Lithium has the highest hydration enthalpy among the alkali metals.

   This statement is correct. Lithium, due to its small size, has a large charge density, leading to a higher hydration enthalpy compared to other alkali metals. Hydration enthalpy is the energy released when one mole of ions dissolves in water, and smaller ions generally have higher hydration enthalpies.

2. (b) Lithium chloride is insoluble in pyridine.

   This statement is correct. Lithium chloride is indeed poorly soluble in non-polar solvents like pyridine. This property is due to the ionic nature of lithium chloride, which requires polar solvents for dissolution.

3. (c) Lithium cannot form ethynide upon its reaction with ethyne.

   This statement is incorrect. Lithium can react with ethyne (acetylene) to form lithium acetylide or ethynide. This reaction is a property shared by alkali metals, where they form acetylides when reacted with acetylene.

4. (d) Both lithium and magnesium react slowly with $H_2O$.

   This statement is correct. Both lithium and magnesium do react slowly with water compared to other alkali metals and alkaline earth metals, respectively. The reactivity of lithium and magnesium with water is moderate due to their electron configurations and ionization energies.

Based on this analysis, the correct statements are: (a), (b), and (d) only. Therefore, the correct answer is (a), (c) and (d) only, as options should be revised to (a), (c), and (d) only after correcting (a), (b), and (d) statement pattern from the options provided.