Question

A conductivity cell has a cell constant of 0.5 cm⁻¹. This cell when filled with 0.01 M sodium chloride solution, has a resistance of 384 ohms at 25°C. Calculate the equivalent conductivity of 0.01 M sodium chloride at 25°C.

Answer 1

Given: Cell constant, (K) = 0.5 cm⁻¹

Resistance, (R) = 384 Ω

Molarity, (C) = 0.01 mol/L

Sodium chloride is a 1:1 electrolyte 

n = 1 equivalent per mole

Specific conductance (κ) =  `"Cell constant"/"Resistance"`

= `0.5/384`

= 0.001302 S cm⁻¹

Equivalent conductivity (Λ_eq) = `(kappa xx 1000)/C`

= `(0.001302 xx 1000)/0.01`

= 130.2 S cm² eq⁻¹

∴ The equivalent conductivity of 0.01 M sodium chloride at 25°C is 130.2 S cm² eq⁻¹.