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Question
CBSEENCH12005933
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Explain with examples the terms weak and strong electrolytes. How can these be distinguished?

Solution
Answer:
(i) Weak electrolytes : An electrolyte that ionizes partially in solution is called a weak electrolyte. The solution formed contains ions which are in equilibrium with un-ionised molecules, e.g., acetic acid dissolves in water to form H3O+ and CH3COO+ ion. The solution contains H3O+ (hydronium ion), CH3COO– (acetate ion) and unionised CH3COOH molecules.



The degree of ionisation of a weak electrolyte is much less than 1. These have low values of molar conductivities at high concentration. Degree of ionisation and molar conductivity both increases with dilution.

(ii) Strong electrolyte : An electrolyte which is almost completely ionised in solution is called a strong electrolyte. The degree of ionisation of a strong electrolyte is 1 or 100% (or nearly so). The solution formed contains ions which are in equilibrium with solid form of strong electrolyte.



Strong electrolyte

Weak electrolyte

1. These have higher molar conductivities at all concentrations.

2. λ°m values increase very slightly with dilution.

3. Degree of ionisation is very high at all concentration i.e., almost fully ionized.

4. Most of the salts like NaCl, KCl, NaNO3, BaCl2 and mineral acids like HCl, H2SO4, HNO3 and NaOH, KOH etc are common examples of strong electrolytes

1. These have much lower conductivities at high concentration.

2. λ°m values increase sharply with dilution.

3. Degree of ionisation is very low at high concentration and increases with dilution.

4. Salts like ammonium acetate, acetic acid, aq NH4OH, aqueous CO2 and organic acids and bases are common examples of weak electrolytes.

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