Question

160g of aqueous solution of urea contains 40% urea by weight. Calculate the molality and mole fraction.​

Answer 1

40% by mass urea solution means 40 gram urea in 100 gram solution.

Thus molality can be given as,

m=(mass of urea in grams/molar mass of urea in gram per mole)*(1000/mass of solvent in grams)

Here mass of solvent can be given as,

Mass of solvent=Mass of solution - mass of solute

=100 - 40

=60

m=(40/60)*(1000/60)

m=200/18

m=11.11 molal