(i) When HCl is dissolved in water, it is ionised into hydrogen ion [or H₃O⁺ ion] and chloride ion.

HCl ⟶ H⁺ + Cl^–

The H⁺ cannot exist independently, therefore, it combines with water molecule to form hydronium ion (H₃O⁺)

H⁺ + H₂O ⟶ H₃O⁺

(ii) When HNO₃ is dissolved in water, it is ionised into hydronium ion and nitrate ion.

HNO₃ ⟶ H⁺ + NO₃^–

H⁺ + H₂O ⟶ H₃O⁺

(iii) When H₂SO₄ is dissolved in water, it is ionised into hydronium ion and sulphate ion.

H₂SO₄ ⟶ 2H⁺ + SO₄^2-

H⁺ + H₂O ⟶ H₃O⁺

(iii) When CH₃COOH is dissolved in water, it is ionised into hydronium ion and acetate ion.

CH₃COOH ⟶ CH₃COO^– + H⁺

H⁺ + H₂O ⟶ H₃O⁺

(iii) When NaOH is dissolved in water, it is ionised into sodium ion and hydroxyl ion.

NaOH ⟶ Na⁺ + OH^–

(iv) When NH₄OH is dissolved in water, it is ionised into ammonium ion and hydroxyl ion.

NH₄OH ⟶ NH₄⁺ + OH^–