Question

At T (K), the molar ionic conductivities of NH; and OH⁻ at infinite dilution are 72 and 198 S cm² mol⁻¹ respectively. The molar conductivity of 0.01 M NH₄OH solution at the same temperature is found to be 9 S cm² mol⁻¹. The percentage dissociation of NH₄OH at this concentration is ____________.

Options

• 3.33

• 7.14

• 12.5

• 4.54

Answer 1

At T (K), the molar ionic conductivities of NH; and OH⁻ at infinite dilution are 72 and 198 S cm² mol⁻¹ respectively. The molar conductivity of 0.01 M NH₄OH solution at the same temperature is found to be 9 S cm² mol⁻¹. The percentage dissociation of NH₄OH at this concentration is 3.33.

Explanation:

\[\ce{λ^0_{NH^+_4}}\] = 72 S cm² mol⁻¹

\[\ce{λ^0_{OH^-}}\] = 198 S cm² mol⁻¹

∴ `∧_("NH"_4"OH")^0` = 72 + 198 = 270 S cm² mol⁻¹

`∧_("NH"_4"OH")` = 9 S cm² mol⁻¹

α = `∧_("NH"_4"OH")/(∧_("NH"_4"OH")^0) = 9/270` = 0.0333

∴ Percentage dissociation = 3.33%