The freezing point of a solution made by dissolving 8.9 g of MgCl₂ in 98 g H₂O is -4.3°C. Kf for water is 1.86°C m-1. The van't Hoff i factor for this solution is ________. A) 1.2 B) 2.3 C) 2.4 D) 2.0 E) 3.0

Question

Quizplus · Accepted Answer

First, we need to calculate the molality of the solution using the mass of solute and mass of solvent:

molality = (8.9 g MgCl2) / (95 g H2O) = 0.094 mol/kg

Next, we can use the freezing point depression equation to solve for the van't Hoff factor (i):

ΔTf = Kf * i * molality

We are given ΔTf (-4.3°C), Kf (1.86°C m^-1), and molality (0.094 mol/kg), so we can plug in and solve for i:

-4.3 = 1.86 * i * 0.094
i = 2.4

Therefore, the van't Hoff i factor for this solution is 2.4, so the answer is choice C.

The Freezing Point of a Solution Made by Dissolving 8