Question

Vitamin K is involved in normal blood clotting. When 1.98 g of vitamin K is dissolved in 25.0 g of camphor, the freezing point of the solution is lowered by 6.63 °C. The freezing point and Kf constant for camphor can be found here. Calculate the molar mass of vitamin K.

Answer 1

we know that

depreesion in freezing point is given by

dTf = kf x m

given

kf = 40

dTf = 6.63

so

6.63 = 40 x m

m = 0.16575

now

we know that

molality = moles of solute x 1000 / mass of solvent (g)

given

mass of sovlent camphor = 25 g

so

0.16575 = moles of solute x 1000 / 25

moles of solute = 4.14375 x 10-3

now

we know that

moles = mass / molar mass

so

4.14375 x 10-3 = 1.98 / molar mass

so

molar mass of vitamin K = 477.83

so

molar mass of vitamin K is 477.83 g / mol