(i) Acid — An acid is a compound which when dissolved in water yields hydronium ions [H3O+] as the only positively charged ion.
HCl (aq) ⇌ H+ + Cl–
H+ + H2O ⇌ H3O+ [hydronium ion]
HCl + H2O ⇌ H3O+ + Cl–
(ii) Base — A base is a compound which reacts with hydronium ions of an acid to give salt and water only.
CuO + 2HCl ⟶ CuCl2 + H2O
Cu(OH)2 + H2SO4 ⟶ CuSO4 + 2H2O
- Bases are oxides or hydroxides of a metal [including ammonium hydroxide]
- Examples of insoluble bases [i.e., not alkalis] — ZnO, PbO, CuO, Fe(OH)2, Pb(OH)2, Cu(OH)2
(iii) Alkali — An alkali is a compound which when dissolved in water yields hydroxyl ions [OH–] as the only negatively charged ions.
NaOH [aq.] ⇌ Na+ + OH– [Hydroxyl or hydroxide ion]
Alkali is a base, soluble in water. [All alkalis are bases, but all bases are not alkalis.]
Examples of soluble bases [i.e., alkalis] — KOH, NaOH [strong alkalis] , Ca(OH)2, NH4OH (weak alkalis).
(iv) Neutralization — It is the process due to which [H+] ions of an acid react completely or combine with [OH–] ions of a base to give salt and water only.
Acid + Base ⟶ Salt + Water
HCl + NaOH ⟶ NaCl + H2O
H+Cl– + Na+OH– ⟶ Na+Cl– + H2O
[H+ (aq) + OH– (aq) ⇌ H2O (l)]
1. Name the apparatus ‘A’.2. Name the substance ‘X’ placed in ‘A’ and the substance ‘Y’ placed in B.3. State the reason for conducting the titration using the apparatus ‘A’ and ‘B’.4. State which solution is transferred to the evaporating dish and evaporated to point of crystallization for obtaining the salt.5. State why titration is not conducted for the preparation of copper [II] sulphate crystals by neutralization.