What is the valency of :

(a) fluorine in CaF₂

(b) sulphur in SF₆

(c) phosphorus in PH₃

(d) carbon in CH₄

(e) Manganese in MnO₂

(f) Copper in Cu₂O

(g) Magnesium in Mg₃N₂

(h) nitrogen in the following compounds :

(i) N₂O₃ (ii) N₂O₅ (iii) NO₂ (iv) NO

Why should an equation be balanced ? Explain with the help of a simple equation.

Define Basic radical.

Balance the following equations.

(a) Al₂O₃ + H₂SO₄ ⟶ Al₂(SO₄)₃ + H₂O

(b) NH₃ + Cl₂ ⟶ NH₄Cl + N₂

(c) C₅H₁₂ (pentane) + O₂ ⟶ CO₂ + H₂O

(d) C₄H₁₀ (butane) + O₂ ⟶ CO₂ + H₂O

(e) FeSO₄ + H₂SO₄ + Cl₂ ⟶ Fe₂(SO₄)₃ + HCl

(f) NaCl + MnO₂ + H₂SO₄ ⟶ NaHSO₄+ MnSO₄ + H₂O + Cl₂

(g) Na₂Cr₂O₇ + HCl ⟶ NaCl + CrCl₃ + H₂O + Cl₂

(h) KMnO₄ + H₂SO₄ + H₂S ⟶ K₂SO₄ + MnSO₄ + H₂O + S