Question

The vapor pressure of water is 23.76 at 25 C. Calculate the vapor pressure of the solution at 25C when 9.889 g of urea is dissolved in 177.2 g of water

Answer 1

P^sat_water-(solvent) = 23.76 torr at 25 degree C mass of urea = 9.889 g mass of water = 177.2 g rightarrow Convert grams into moles then calculate mole fraction molecular weight of urea = 60.06 g/mol moles of urea = 9.889 g/60.06 g/mol = 0.1646 mol molecular weight of water = 18.015 g/mol moles of water = 177.2 g/18.015 g/mol = 9.836 mol rightarrow mole fraction of water = 9.836/9.836 + 0.1646 = 0.983 vapor pressure of solution = mole fraction solvent times vapor pressure of the pure solvent p^vap_solution = (p^vap_solvent) (x_solvent) = 23.76 times 0.983 p_solution = 23.35 torr