chem 不明

Which of the following compounds would produce a gaswhen heatedwith concentrated sulphuric acid ?
A: sodiumsulphate
B: calciumchloride
C: magnesiumoxide
D: aluminiumhydroxide


The answer is B: calcium chloride.

A: No gas is formed.
There is no reaction between sodium sulphate and concentrated sulphuric acid.

B. Hydrogen chloride gas is formed.
When heated, calcium chloride reacts with concentrated sulphuric acid to givehydrogen chloride gas.
CaCl2(s) + 2H2SO4(aq) → Ca(HSO4)2(aq) + 2HCl(g) .. [gentle heating]
CaCl2(s) + H2SO4(aq) → CaSO4(s) + HCl(g) .. [strong heating]

C. No gas is formed.
Neutralization occurs between magnesium oxide and concentrated sulphuric acidto give magnesium sulphate and water.
MgO(s) + H2SO4(aq) → MgSO4(aq) + H2O(l)

D. No gas is formed.
Neutralization occurs between aluminium hydroxide and concentrated sulphuricacid to give aluminium hydroxide and water.
2Al(OH)3(s) + 3H2SO4(aq) → Al2(SO4)3(aq)+ 3H2O(l)

Concentrated sulphuric acid is H2SO4(l), not H2SO4(aq)