Chemistry
Define the following as per ionic theory with examples and ionic equations wherever relevant :
(i) acid (ii) base (iii) alkali (iv) neutralization
Answer
(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)]
Related Questions
Differentiate between:
(i) Organic and inorganic acids.
(ii) Hydracids and oxyacids with examples.
State on what basis does the strength of an acid and an alkali depend on.
Name the ions formed when — HCl; HNO3; H2SO4; CH3COOH; NaOH and NH4OH ionise in aq. soln.
Differentiate between (i) strong and weak acid (ii) strong and weak alkali with suitable examples and ionic equations.