🤓 Based on our data, we think this question is relevant for Professor Weiss' class at OREGONSTATE.
The freezing point of t-butanol is 25.50°C and Kf is 9.1°C • kg/mol. Usually t-butanol absorbs water on exposure to air. If the freezing point of a 10.0-g sample of t-butanol is 24.59°C, how many grams of water are present in the sample?
We’re being asked to determine the mass of water present in a 10.0 g sample of t-butanol with a freezing point of 24.59°C.
Recall that the freezing point of a solution is lower than that of the pure solvent and the change in freezing point (ΔTf) is given by:
The change in freezing point is also related to the molality of the solution:
i = van’t Hoff factor
m = molality of the solution (in m or mol/kg)
Kf = freezing point depression constant (in ˚C/m)
Recall that the molality of a solution is given by:
To solve this problem, we shall follow these steps
Step 1: Calculate for ΔTf.
Step 2: Determine the molality of the solution.
Step 3: Calculate the mass of H2O.