Question

A solution of an organic compound was prepared by dissolving 6.8 g in 0.1 litre of water. Calculate the osmotic pressure of this solution at 25°C.

(Molecular mass of organic compound = 321.45 g mol⁻¹)

Answer 1

Given: Mass of solute (w) = 6.8 g

Molecular mass of solute (M) = 321.45 g mol⁻¹

Volume of solution (V) = 0.1 L

Temperature (T) = 25°C + 273.15 = 298.15 K

Ideal gas constant (R) = 0.0821 L atm K⁻¹ mol⁻¹

Formula: Number of moles (n) = `w/M`

= `(6.8)/(321.45)`

= 0.02115 mol

The osmotic pressure formula is:

`pi = (nRT)/V`

= `(0.02115 xx 0.0821 xx 298.15)/(0.1)`

= `0.5177/0.1`

= 5.177 atm