What do you understand by precipitation reaction? Explain with an example.

(a) What are double displacement reactions?

(b) Give an example of a double displacement reaction, where gas is evolved.

State the type of reactions each of the following represent and balance the ones that are not balanced.

(a) Cl₂ + 2KBr ⟶ 2KCl + Br₂

(b) NaOH + HCl ⟶ NaCl + H₂O

(c) 2HgO ⟶ 2Hg + O₂ ↑

(d) Fe + CuSO₄ ⟶ FeSO₄ + Cu

(e) PbO₂ + SO₂ ⟶ PbSO₄

(f) 2KClO₃ ⟶ 2KCl + 3O₂ ↑

(g) 2H₂O₂ ⟶ 2H₂O + O₂ ↑

(h) KNO₃ + H₂SO₄ ⟶ HNO₃ + KHSO₄

(i) CuO + H₂ ⟶ Cu + H₂O

(j) CaCO₃ ⟶ CaO + CO₂ ↑

(k) NH₄Cl ⟶ NH₃ + HCl

(l) PbO + 2HNO₃ ⟶ Pb(NO₃)₂ + 2H₂O

(m) AgNO₃ + NaCl ⟶ AgCl ↓ + NaNO₃

Which of the of following is not a chemical change.

1. Rusting of iron
2. Iron is magnetised
3. Potassium is dissolved in water
4. Magnesium wire is burnt