• # question_answer A metal M reacts with ${{N}_{2}}$ to give a compound 'A' $({{M}_{3}}N)$. 'A' on heating at high temperature gives back 'M' and 'A' on reacting with ${{H}_{2}}O$gives a gas 'B'. 'B' turns $CuS{{O}_{4}}$solution blue on passing through it. A and B can be  [DCE 2003] A) Al and $N{{H}_{3}}$ B) Li and $N{{H}_{3}}$ C) Na and $N{{H}_{3}}$ D) Mg and $N{{H}_{3}}$

Lithium form nitride on heating with nitrogen. Lithium nitride gives ammonia when heated with ${{H}_{2}}O$. Ammonia gas form tetrammine copper complex with $CuS{{O}_{4}}$ solution. $6Li+{{N}_{2}}\to 2L{{i}_{3}}N$ $L{{i}_{3}}N+3{{H}_{2}}O\to 3LiOH+N{{H}_{3}}$ $CuS{{O}_{4}}+4N{{H}_{3}}\to [Cu{{(N{{H}_{3}})}_{4}}]S{{O}_{4}}$