Question

At 298 K, the molar conductivities at infinite dilution of sodium propionate (CH₃CH₂COONa), HCl and NaCl are 85.9, 426.1 and 126 ohm⁻¹ cm² mol⁻¹ respectively. Calculate the molar conductivity of propionic acid at infinite dilution.

Answer 1

Given: `Lambda_m^0​` (CH₃CH₂COONa) = 85.9 Ω⁻¹ cm² mol⁻¹

`Lambda_m^0` (HCl) = 426.1 Ω⁻¹ cm² mol⁻¹

`Lambda_m^0` (NaCl) = 126.0 Ω⁻¹ cm² mol⁻¹

To calculate the molar conductivity at infinite dilution `(Lambda_m^0)` of propionic acid (CH₃CH₂COOH), we use Kohlrausch’s Law of Independent Migration of Ions:

\[\ce{\Lambda{^{0}_{m}}​(CH3CH2COOH) = \Lambda{^{0}_{m}}(CH3CH2COONa) + \Lambda{^{0}_{m}}​(HCl) - \Lambda{^{0}_{m}}​(NaCl)}\]

= 85.9 + 426.1 − 126.0

= 386 Ω⁻¹ cm² mol⁻¹