Question

Name the gas evolved in each of the following cases:
(i) Iron sulphide is treated with aqueous sulphuric acid.
(ii) Calcium metal is added into water
(iii) Ammonium salt when heated with alkali.
(iv) Action of heat on copper nitrate
(v) Addition of dil hydrochloric acid on Zinc metal

Answer 1

Gases evolved in the given reactions :

i) When iron sulphide is treated with aqueous sulphuric acid, hydrogen suplhide (H₂S) gas is evolved with a smell of rotten eggs.

FeS + aq. H₂SO₄  → FeSO₄ + H₂S

(ii) When calcium metal is added into water, hydrogen gas is evolved.

Ca + 2H₂O  → Ca(OH)₂ + H₂

(iii) When an ammonium salt is heated with an alkali, a pungent smelling gas is evolved, which is ammonia.

NH₄Cl + NaOH  → NaCl + NH₃ + H₂O

(iv) When copper (II) nitrate is heated, a reddish brown gas of nitrogen dioxide is evolved along with oxygen.

2Cu(NO₃)₂ + ∆  → 2CuO + 4NO₂ + O₂

(v) Addition of dilute hydrochloric acid to zinc metal produces hydrogen gas.

Zn + 2 dil. HCl  → ZnCl₂ + H₂