Question

When alkaline earth metals dissolve in ammonia, they form coloured solution like alkali metals. Which of the following observations regarding the reaction are correct?

(i) Dilute solutions are bright blue in colour due to solvated electrons.

(ii) These solutions decompose to form amides and hydrogen

(iii) From this solution the ammoniates $\lbrack M(NH_{3})_{6}\rbrack^{2 +}$can be recovered by evaporation.

• A. (i) and (ii)
• B. (i), (ii)and (iii)
• C. (ii) and (iii)
• D. Only (i)

Answer 1

Answer: (B)

(i), (ii)and (iii)

Answer 2

: All the observations are correct.

$M \rightarrow M^{2 +} + 2e^{-}$

$2NH_{3} + 2e^{-} \rightarrow 2NH_{2}^{-} + H_{2}$

$M^{2 +}2NH_{2}^{-} \rightarrow M(NH_{2})_{2}\overset{\quad evaporation\quad}{\rightarrow}\lbrack M(NH_{3})_{6}\rbrack^{2 +}$

$\lbrack M(NH_{3})_{6}\rbrack^{2 +} \rightarrow M(NH_{2})_{2} + 4NH_{3} + H_{2}$