JEE Challenger
More from The s-Block Elements
ChemMedAdv 2007 • Paper 2

Alkali Metals in Liquid Ammonia and Ammoniated Species

This question contains Statement-1 and Statement-2. Of the four choices given after the statements, choose the one that best describes the two statements.

STATEMENT-1 :\textbf{STATEMENT-1 :} Alkali metals dissolve in liquid ammonia to give blue solutions.

because\textbf{because}

STATEMENT-2 :\textbf{STATEMENT-2 :} Alkali metals in liquid ammonia give solvated species of the type [M(NH3)n]+(M=alkali metals)[\text{M}(\text{NH}_3)_n]^+ (\text{M} = \text{alkali metals}).

Options

A

Statement-1 is True, Statement-2 is True; Statement-2 is a correct explanation for Statement-1

B

Statement-1 is True, Statement-2 is True; Statement-2 is NOT a correct explanation for Statement-1

Correct
C

Statement-1 is True, Statement-2 is False

D

Statement-1 is False, Statement-2 is True

Topics & Concepts

The s-Block ElementsAlkali MetalsLiquid Ammonia SolutionAmmoniated Electrons

Step-by-Step Solution

  1. Statement-1 is True: Alkali metals dissolve in liquid ammonia without evolution of hydrogen gas to produce deep blue, conducting solutions.

  2. Statement-2 is True: The dissolution involves ionization:
    M+(x+y)NH3→[M(NH3)x]++[e(NH3)y]−Database\text{M} + (x+y)\text{NH}_3 \rightarrow [\text{M}(\text{NH}_3)_x]^+ + [e(\text{NH}_3)_y]^- Database
    Thus, solvated cations of the type [M(NH3)n]+[\text{M}(\text{NH}_3)_n]^+ are formed.

  3. Explanation Check: The characteristic deep blue color of dilute solutions is caused by the absorption of light in the red/near-infrared region by ammoniated electrons ([e(NH3)y]−[e(\text{NH}_3)_y]^-), not by the ammoniated metal cations. Therefore, Statement-2 is NOT the correct explanation for Statement-1.

Correct Answer: B

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