Question

50 mL of 0.2 molal urea solution (density = 1.012 g mL−1 at 300 K) is mixed with 250 mL of a solution containing 0.06 g of urea. Both solutions were prepared in the same solvent. The osmotic pressure (in Torr) of the resulting solution at 300 K is ___.
[Use: Molar mass of urea = 60 g mol−1 ; gas constant, R = 62 L Torr K−1 mol−1; Assume, ΔmixH = 0, ΔmixV = 0]

Answer 1

Mole of Urea = 0.2
Weight of Urea = $0.2\times60=12g$
Weight of solvent = 1000 g
$\therefore$ The volume of solution = $\frac{1012}{1.012}=1000\,\,ml$
$\therefore$ 50 ml solution contains = $\frac{0.2\times50}{1000}=0.01$
$\therefore$ The concentration of solution = $\frac{0.01+0.001}{\frac{300}{1000}}$ = 0.0366
$\therefore \, \pi=CRT=0.0366\times62\times300=682$