In: Chemistry
The density of a 0.438 M solution of potassium chromate (K2CrO4) at 298 K is 1.063 g/mL. a.Calculate the vapor pressure of water above the solution. The vapor pressure of pure water at this temperature is 0.0313 atm. Assume complete dissociation.
raoults law
P0-P/P0 = i*Xsolute
P = vapor pressure of water above the solution = ?
p0 = vapor pressure of pure water at this temperature = 0.0313 atm
Molarity = w/w%*d*10 / Mwt
Mwt = molarmass of K2CrO4 = 194.2 g/mol
density = 1.063 g/ml
w/w% = 0.438*194.2/(1.063*10) = 8% by mass
means 8 g K2cro4 present in 100 g solution
no of mole of K2cro4 = w/mwt = 8/194.2 = 0.04 mol
no of mole of water in solution = (100-8)/18 = 5.11 mol
, XK2CrO4 = molefraction of K2CrO4 = 0.04/(5.11+0.04) = 0.0077
i = vanthof factor of K2CrO4 = 3
(0.0313-p)/0.0313 = 3*0.0077
p = vapor pressure of water above the solution = 0.0306 atm