Question

How many grams of urea, (NH2)2CO (the product of protein metabolism in animals) must be dissolved in 146.3 g of H2O to cause a freezing point depression of 1.996 degrees celsius? Kf=1.86 C/m

Answer 1

Ans :

Freezing point depression = kf x m

where m is molality

putting values :

1.996 = 1.86 x m

m = 1.073 m

molality = mol / mass of solvent in kg

1.073 = n / 0.1463

n = 0.157 mol

Mass of urea = mol x molar mass

= 0.157 mol x 60.06 g/mol

= 9.43 grams