calculate the molality and van\'t Hoff factor for the following solutions (a) 0.

Question

calculate the molality and van't Hoff factor for the following solutions
(a) 0.549 mass % KCl, freezing point = -0.234°C
(b) 1.01 mass % H2SO4, freezing point = -0.423°C

Caiculate the molality and van't Hoff factar (n for the following aqusous solutions. (a) 0.549 mass % KCl, freezing pont-0.2345c molality van't Hat factor (b) 1.01 mass % H2SO4, freezing point =-0.423°C molality 71 van't Hof fector van't Hoff factor In . study designed to prepare new gasoline-resistant coatings, a polymer chemist dissolv

Explanation / Answer

molality = moles of solute/kg of solvent

dTf = -iKfm

with,

i = van't hoff factor

Kf = freezing point constant for solvent = 1.86 oC/m for water

m = molality

(a) 0.549 mass % KCl

Let the total amount of solution be 100 g

amount of solvent = 100 - 0.549 = 99.451 g

molality = 0.549 g/74.55 g/mol x 0.099451 kg = 0.074 m

van't hoff factor for KCl = dTf/-Kfm = -0.234/-1.86 x 0.074 = 1.70 or 2

(b) 1.01 mass% H2SO4

Let the total amount of solution be 100 g

amount of solvent = 100 - 1.01 = 98.99 g

molality = 1.01 g/98.079 g/mol x 0.09899 kg = 0.104 m

van't hoff factor for H2SO4 = -0.423/-1.86 x 0.104 = 2.2 or 2

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