(A) Sodium nitrite (0.1 mol) reacts with sodium metal (0.3 mol) to give compound X (0.2 mol) and nitrogen gas (0.05 mol). Compound X (0.1 mol) reacts with oxygen (0.05 mol) to give compound Y (0.1 mol) only. Identify X and Y, and write balanced chemical equations for the reactions described.

(B) A group 2 metal (0.1 mol) is heated with carbon (0.2 mol) at 1100 °C to produce a single compound X (0.1 mol). When compound X (0.1 mol) is heated in excess N₂(g) at 1100 °C, solid carbon (0.1 mol) is produced along with compound Y (0.1 mol). The group 2 metal sulfate is used in plaster of Paris and the anion in compound Y is isoelectronic with CO₂. Identify compounds X and Y, write balanced chemical equations for the reactions described, and describe the shape of the anion in Y.