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 $[M(NH_3)_6]^{2+}$ can be recovered by evaporation.

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

Answer 1

Answer: (B)

Only (i), (ii) and (iii)

Answer 2

All the observations are correct. $M \to M^{3+} +2e^-$ $2NH_3+2e^- \to 2NH^-_2 +H_2$ $M^{2+}+2NH^-_2 \to M(NH_2)_2 {->[{\text{eyporation}}]} [M(NH_3)_6]^{2+}$ $[M(NH_3)_6]^{2+} \to M(NH_2)_2 + 4NH_3 + H_2$