Answer to Question #33028 in Physical Chemistry for cedric

Question

the vapour pressure of h20 at 20degrees Celsius is 17mmhg.calculate the vapour pressure of solution of 3g of urea in 50g of water

Answer 1

To solve this we can use Raoult's law: p = p'x
x = x(H₂O) = 50/18 = 2.78 moles;
moles of urea(CH₄N₂O) = 3/60 = 0.05 moles;
mole fraction of water in solution = 2.78/(2.78 + 0.05) = 0.98
p'x = 17*0.98 = 16.66