Calculate the freezing point of a solution made by dissolving 3.50 g of potassium chloride (? = 74.55 g/mol) in 100.0 g of water. Assume ideal behavior for the solution; K_f = 1.86$\degree$C/m. A) -1.7$\degree$C B) -0.9$\degree$C C) 0.0$\degree$C D) 0.9$\degree$C E) 1.7$\degree$C

Question

Quizplus · Accepted Answer

First, we need to calculate the molality of the solution:

molality = moles of solute / mass of solvent in kg

moles of solute = 3.50 g / 74.55 g/mol = 0.0469 mol
mass of solvent = 100.0 g / 1000 = 0.1000 kg

molality = 0.0469 mol / 0.1000 kg = 0.469 m

Next, we can use the freezing point depression equation to calculate the change in freezing point (ΔT):

ΔT = Kf x molality

ΔT = 1.86 ºC/m x 0.469 m = 0.87354 ºC

Finally, we can calculate the freezing point of the solution by subtracting ΔT from the freezing point of pure water (0 ºC):

freezing point = 0 ºC - 0.87354 ºC = -0.87354 ºC ≈ -1.7 ºC

Therefore, the best choice is A.

Calculate the Freezing Point of a Solution Made by Dissolving °\degree°

Calculate the Freezing Point of a Solution Made by Dissolving $\degree$