(a) A group 2 metal, M, dissolves in liquid NH₃, and from the solution, compound A can be isolated. A slowly decomposes to B with liberation of NH₃ and a gas C. Metal M gives a crimson flame test; through blue glass, the flame appears pale purple. Suggest identities for M, A, B and C.

(b) The group 2 metal X occurs naturally in great abundance as the carbonate. Metal X reacts with cold water, forming compound D, which is a strong base. Aqueous solutions of D are used in qualitative tests for CO₂. X combines with H₂ to give a saline hydride that is used as a drying agent. Identify X and D. Write equations for the reaction of X with H₂O and of the hydride of X with H₂O. Explain how you would carry out a qualitative test for CO₂ using an aqueous solution of D.