Question

Determine the ideal value of the van’t hoff factor for SrSO₄ at infinite dilution. Then, use that value to determine the freezing point of a solution when 15.00 g is dissolved into 150 mL of water.

Round your answer to the tenths digit.

Answer 1

SrSO4 will break into 2 ions Sr⁺² and SO4^2- . So ideal Van't Hoff factor(i) is 2.

T = i * Kf * molality of solute

T is depression in freezing point of water.

Kf for water is 1.86 C/m

and molality of solution = Number of moles of solute/ Mass of solvent

So, number of moles of SrSO4 = 15/MW of SrSO4 = 15/ 183.68 = 0.0816

Mass of solvent = 150g = 0.15 kg ( Density of water = 1g/ml)

So, molality = 0.0816/0.15

= 0.544m

SO,

T = 2 * 1.86 C/m * 0.544m

= 2.02 C

So, freezing point of water = Actual freezing point of water - T

= 0C - 2.02C

= -2.02C or 270.98K