The freezing point of a salt and water mixture is -0.58 C. The freezing point of an unknown ionic solution (0.100 m) is -1.04 C.
1. Determine the freezing point depression for the ionic solution.
2. How do you determine the van't Hoff factor for the ionic solution?
Please help me. I think I got the first part, with -0.58-(-1.04) = 0.46 C. That's the freezing point depression, right? Though I'm not sure what the water and salt solution relates to it. How do I find the van't hoff factor? I know the formula to use is T=i*Kf*m
T would be 0.46, m would be .100, but what would Kf be? I know the Kf value for water as a solvent is 1.86, but water wasn't used as a solvent here... So I'm not sure how to proceed
I don't get it. I can't figure out exactly what the question is (yes, I know they want i). What is the connection between the two statements? Are these two problems? What does "a salt solution" mean? Is that NaCl or some other salt. Is it the same salt as in the unknown solution. How do you know the unknown ionic solution is not in water. If not water what is the solvent. My personal feeling is that it is water.
To determine the freezing point depression for the ionic solution, you are correct in calculating the difference between the freezing point of the pure solvent (water) and the freezing point of the solution: -0.58 °C - (-1.04 °C) = 0.46 °C. This value represents the freezing point depression.
Now, to determine the van't Hoff factor, you need to consider the number of particles the solute dissociates into when it dissolves in the solvent. The van't Hoff factor (i) accounts for this dissociation and is calculated using the formula:
i = (ΔTf) / (Kf * m)
Where:
ΔTf is the freezing point depression (0.46 °C),
Kf is the molal freezing point depression constant, and
m is the molality of the solute (0.100 m).
In this case, you mentioned that water was not used as the solvent. Therefore, the Kf value for water as a solvent (1.86 °C/m) is not applicable. Instead, you need to determine the specific Kf value for the solvent used.
The Kf value represents the freezing point depression caused by a 1 molal concentration of a solute in the given solvent. If you can identify the solvent used in the ionic solution, you can reference a table or look up the specific Kf value for that solvent.
Once you have the Kf value for the solvent, you can substitute it into the formula above along with the known values of ΔTf and m to solve for the van't Hoff factor (i).