Question

A gas, A obtained by heating aluminum with sodium hydroxide was passed over a black solid, B at 773K when a grey metal, C and a colourless liquid, D were obtained. The metal C displaces copper from copper sulphate solution and becomes passive on treatment with cone. IINO3. Identity A, B, C and D and explain all the reactions.

Answer 1

(i) 2Al(s) + 2NaOH(aq) + 2H₂O(l) → 2NaAlO₂(aq) + 3H₂(g) Dihydrogen(A)

(ii) Fe₃O₄(s) {Black solid(B)} + 4H₂(g) \(\overset{773\,K}{\longrightarrow}\) 3Fe(s) Grey metal(C) + 4H₂O Water(D)

(iii) Fe(s) + CuSO₄(aq) → FeSO₄(sq) + Cu(s)

(iv) 3Fe(s) + 8IINO₃(sq) → FeO.Fe₂O₃(s) {Ferrosoferri oxide(B)} + 8NO₂(g) + 4H₂O(l)

Iron is rendered passive due to the formation of ferrosoferric oxide or magnetic oxide {black solid (B)}