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.
Differentiate between (i) strong and weak acid (ii) strong and weak alkali with suitable examples and ionic equations.
Name the ions formed when — HCl; HNO3; H2SO4; CH3COOH; NaOH and NH4OH ionise in aq. soln.
State on what basis does the strength of an acid and an alkali depend on.