From the equation :

(NH₄)₂Cr₂O₇ ⟶ N₂(g) + 4H₂O(g) + Cr₂O₃

Calculate:

(i) the quantity in moles of (NH₄)₂Cr₂O₇ if 63 gm of (NH₄)₂Cr₂O₇ is heated.

(ii) the quantity in moles of N₂ formed.

(iii) the volume in litres or dm³ of N₂ evolved at s.t.p.

(iv) the mass in grams of Cr₂O₃ formed at the same time.

[H = 1, Cr = 52, N = 14]

Aluminium carbide reacts with water according to the following equation :

Al₄C₃ + 12H₂O ⟶ 4Al(OH)₃ + 3CH₄

(i) State what mass of aluminium hydroxide is formed from 12 g. of aluminium carbide.

(ii) State the volume of methane at s.t.p. obtained from 12 g of aluminium carbide.

[relative molecular weight of Al₄Cl₃] = 144 ; Al(OH)₃ = 78

Copper [II] sulphate soln. reacts with sodium hydroxide soln. to form copper hydroxide according to the equation :

2NaOH + CuSO₄ ⟶ Na₂SO₄ + Cu(OH)₂↓

What mass of copper hydroxide is precipitated by using 200 g of sodium hydroxide.

[H = 1, O = 16, Na = 23, S = 32, Cu = 64]