Question

Name the evolved gases in following cases:-
(i) Exposure of chlorine water to sunlight.
(ii) Addition of dilute sulphuric acid to sodium hydrogen sulphite
(iii) Action of heat on calcium carbonate
(iv) Reaction between concentrated hydrochloric acid and manganese dioxide
(v) Addition of concentrated sulphuric acid to potassium chloride

Answer 1

Answer:

hydrogen ..................

Answer 2

Gases evolved in the given reactions :

i) • Exposure of chlorine water to sunlight evolves colourless and odourless oxygen gas.

• Chlorine water is a solution of chlorine in water, forming hypochlorous acid and hydrochloric acid.

Cl₂ + H₂O → HClO + HCl

• When exposed to sunlight, the hypochlorous acid decomposes into hydrochloric acid and nascent oxygen.

HClO + sunlight →  HCl + [O]

• The nascent oxygen atoms combine to give dioxygen gas.

[O] + [O]  → O₂

ii) Addition of dilute sulphuric acid to sodium hydrogen sulphite evolves sulphur dioxide gas with a pungent odour.

NaHSO₃ + dil. H₂SO₄  → NaHSO₄ + SO₂ + H₂O

iii) Action of heat on calcium carbonate produces colourless and odourless carbon dioxide gas.

• Calcium carbonate, on heating, decomposes into calcium oxide and carbon dioxide.

CaCO₃ + ∆  → CaO + CO₂

iv) Reaction between concentrated hydrochloric acid and manganese dioxide releases chlorine gas with a pungent odour.

MnO₂ + 4 conc. HCl  → MnCl₂ + Cl₂ + 2H₂O

v) Addition of concentrated sulphuric acid to potassium chloride evolves hydrogen chloride gas with a strong smell.

2KCl + conc. H₂SO₄ →  K₂SO₄ + 2HCl