Question

Consider the following statements.
(i) Molar conductance of ${\text{H}}^{+}$ is much higher than those of other ions
(ii) Equivalent conductivity and molar conductivity increase with dilution
(iii) Specific conductivity decreases with dilution
(iv) Conductance $K^{+}<N{a}^{+}<L{i}^{+}$ in water
Identify the correct statement.

• A. (ii) only
• B. (iii) only
• C. (i), (ii) and (iii)
• D. (ii), (iii) only

Answer 1

The correct option is D (ii), (iii) only

Molar conductivity increases with dilution though conductivity always decreases with decrease in concentration. But molar conductivity is the conductance of that volume solution containing one mole of electrolyte. As the total volume of solution containing one mole of electrolyte increases, the decrease in conductivity due to dilution is more than compensated by increase in its volume of solution that contains one mole of the electrolyte. Also equivalent conductance increases with dilution because it is the product of specific conductivity and the volume V , containing one mole of electrolyte. Although the specific conductance decreases with dilution, this decrease is more compensated by increase in volume.Specific conductivity decreases with dilution as number of ions per unit volume decreases on dilution.

(iv) will be $K^{+}>N{a}^{+}>L{i}^{+}$ due to the hydration enthalpy of $L{i}^{+}$ is most. It is highly hydrated due to which it should have low conductance in water.