What do you observe in the following cases?

(a) Lead nitrate is heated.

(b) Silver chloride is exposed to sunlight.

(c) Hydrogen peroxide is exposed to sunlight

(d) H₂S gas is passed through copper sulphate solution

(e) Barium chloride is added to sodium sulphate solution.

(f) Water is added to quick lime

(g) Sodium chloride solution is added to silver nitrate solution.

(a) When white crystalline solid Lead nitrate is heated, it decomposes into a buff yellow residue of lead monoxide. Reddish brown gas Nitrogen dioxide and colourless gas Oxygen are evolved.

$\underset{\text{[lead nitrate (white)]}}{2\text{Pb(NO}$3)2} \overset{\Delta}{\longrightarrow} \underset{\text{[litharge - buff yellow]}}{2\text{PbO}} + \underset{\text{[Nitrogen dioxide]}}{4\text{NO}2} + \underset{\text{[Oxygen]}}{\text{O}2}

(b) When silver chloride (white) is exposed to sunlight, it undergoes photochemical decomposition forming a grey metal, silver and a greenish yellow gas, chlorine.

2AgCl (s) $\xrightarrow{\text{ sunlight}}$ 2Ag (s) + Cl₂ (g)

(c) When hydrogen peroxide is exposed to sunlight, it changes to water and colourless, odourless oxygen gas is evolved.

2H₂O₂ $\xrightarrow{\text{ sunlight}}$ 2H₂O + O₂ ↑

(d) When H₂S is passed through copper sulphate solution, a black precipitate of copper sulphide is obtained

CuSO₄ + H₂S ⟶ CuS [black] + H₂SO₄

(e) White coloured precipitate of barium sulphate is formed when sodium sulphate is mixed with barium chloride.

Na₂SO₄ (aq.) + BaCl₂ (aq.) ⟶ 2NaCl (aq.) + BaSO₄ [white ppt.] ↓

(f) When calcium oxide (quick lime) combines with water, a vigorous reaction takes place with the liberation of a large amount of heat (exothermic reaction) and calcium hydroxide is formed. Heat produced boils the water and a hissing sound is produced.

CaO (s) + H₂O (l) ⟶ Ca(OH)₂ (s) + Heat

(g) When sodium chloride is added to the silver nitrate solution, a white curdy precipitate of silver chloride is formed.

NaCl (aq.) + AgNO₃ (aq.) ⟶ AgCl (white ppt.) ↓ + NaNO₃ (aq.)