Question

A solution of a substance having mass 1.8 x 10^-3 kg has the osmotic pressure of 0.52 atm at 280 K. Calculate the molar mass of the substance used.
[Volume = 1 dm³, R = 8.314 J K^-1 mol^-1]

Answer 1

Given: Volume (V) = 1dm³ = 1L
Mass of substance (W₂) = 1.8 x 10^–3 kg = 1.8g
Osimotic pressure (π) = 0.52 atm
R = 8.314 J K^–1 mol^–1 or R = 0.082 L atm K^–1 mol^–1
Temperature (T) = 280K

`pi=(W_2RT)/(M_2V)`

`M_2=(W_2RT)/(piV)`

`M_2=(1.8xx0.082xx280)/(0.52xx1)`

`M_2=79.47 g mol^-1`