QQuestion
K, L and M are beakers containing three different solutions as shown below.
Name the beaker which:
(a) contains only ions.
(b) contains only molecules.
(c) has pH less than 7.
✓Answer
(a) L — Sodium chloride is a strong electrolyte and ionises completely in water, dissociating fully into Na+ and Cl− ions.
NaCl ⟶ Na+ + Cl−
(b) M — Distilled water consists almost entirely of H2O molecules and contains no ions (its self-ionisation is negligible).
(c) K — Aqueous acetic acid is acidic in nature (it is a weak acid which partially ionises to give H+ ions), and hence has a pH less than 7.
CH3COOH ⇌ CH3COO− + H+
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