Question

the osmotic pressure of a 0.25M urea solution is 2.67 atm. what will be the osmotic pressure of a 0.25M SOLUTION OF POTTASIUM SULPHATE?

Answer 1

Urea is an non electrolyte, hence its Van't Hoff factor is 1
Osmotic pressure of urea solution = 2.67atm
Concentration of urea solution = 0.25M
Osmotic pressure, $\pi$ = CRT
2.67 = 0.25 RT ... equation-1

Potassium sulphate is an electrolyte, it dissociate as,
K₂SO₄ $\to$ 2K⁺ + SO₄^2-

Van't Hoff factor = $\frac{\mathrm{Number}\mathrm{of}\mathrm{articles}\mathrm{after}\mathrm{dissociation}}{\mathrm{Number}\mathrm{of}\mathrm{articles}\mathrm{before}\mathrm{dissociation}}=\frac{3}{1}=3$

Concentration of potassium sulphate = 0.25M
Osmotic pressure of potassium sulphate, $\pi$ = i CRT
$\pi$ = 3$\times$ 0.25 RT ... equation-2
Putting equation-1 in equation-2 we get,
Osmotic pressure of potassium sulphate, $\pi$ = 8.01atm