Question

Calculate the freezing point of an aqueous 0.18 m solution of FeCl₃ using a van't Hoff factor of 3.1. (Assume that Kf of water is 1.86∘C/m.) Express the temperature to two significant figures and include the appropriate units.

a) -0.78°C
b) -0.42°C
c) -1.21°C
d) -1.86°C

Answer 1

The freezing point of a 0.18 m FeCl₃ solution using a van't Hoff factor of 3.1 is calculated to be approximately -1.03°C, which is not exactly represented by the options given.

Step-by-step explanation:

To calculate the freezing point depression of a 0.18 m solution of FeCl₃ using a van't Hoff factor of 3.1, we use the formula ΔTf = iKfm, where ΔTf is the change in freezing point, i is the van't Hoff factor (which is 3.1 in this case), Kf is the freezing point depression constant for water (1.86°C/m), and m is the molality (0.18 m). Plugging these values into the formula, we get:

ΔTf = (3.1)(1.86°C/m)(0.18 m) = 1.03476°C.

The normal freezing point of water is 0°C, so the freezing point of the solution is:

0°C - 1.03476°C = -1.03°C.

Expressed to two significant figures, the freezing point of the aqueous FeCl₃ solution is -1.03°C. None of the options provided match this value exactly, but the closest option appears to be -1.21°C. However, it's important to double-check calculations and the provided options for any discrepancies.