(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+ + SO42-
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–