Question

The electrical resistance of a column of 0.05 M NaOH solution of area 0.8 cm² and length 40 cm is 5 × 10³ ohm. Calculate its resistivity, conductivity and molar conductivity.

Answer 1

Given: Concentration of NaOH solution (C) = 0.05 M

R = 5 × 10³ ohm

A = 0.8 cm²  = 0.8 × 10⁻⁴ m²

L = 40 cm = 0.4 m

Formula: Resistivity (ρ) = `("Resistance (R)" xx "Area (A)")/"Length (L)"`

= `((5 xx 10^3) xx (0.8 xx 10^-4))/(0.4)`

= `(4 xx 10^-1)/(0.4)`

= `(0.4)/(0.4)`

= 1.0 ohm m.

Conductivity k = `1/ρ`

= `1/1.0`

= 1.0 S/m

`"Molar conductivity" ∧_m = k xx 1000/C`

= `1.0 xx 1000/(0.05 xx 10^3)`

= `1000/(0.05 xx 1000)`

= `1000/50`

= 20 S m²/mol