Which of the following will have the smallest freezing point depression?
0.1158 m NaF
0.1158 m Na2SO4
0.1158 m K2SO4
0.1158 m Fe(NO3)3
delta T = Kf*m
If Kf is a constant, then what is true for m to get the smallest delta T?
To determine which of the given solutions will have the smallest freezing point depression, we need to consider the properties of each compound and their effect on freezing point depression.
Freezing point depression is a colligative property, meaning it depends on the number of particles dissolved in a solution rather than the specific identity of the solute. Specifically, the freezing point depression is dependent on the molality (m) of the solute particles.
The formula to calculate the freezing point depression (ΔTf) is as follows:
ΔTf = Kf * m
Where:
ΔTf = Freezing point depression
Kf = Cryoscopic constant (a constant specific to the solvent)
m = Molality of the solute particles
In this case, all the solutions have the same molality (0.1158 m), so the compound with the lowest cryoscopic constant (Kf) will result in the smallest freezing point depression.
To determine which compound has the lowest cryoscopic constant, we need to consider the solvent used. The solvent is not mentioned in the question, so we can't determine the exact values of Kf for each compound.
In general, salts with more ions dissociating in water will have a greater impact on the freezing point depression. Therefore, we can make an educated guess based on the number of ions each compound will produce when dissociated in water.
Considering the dissociation of each compound:
1. NaF: NaF dissociates into Na+ and F- ions (2 ions in total).
2. Na2SO4: Na2SO4 dissociates into 2 Na+ ions and 1 SO4^2- ion (3 ions in total).
3. K2SO4: K2SO4 dissociates into 2 K+ ions and 1 SO4^2- ion (3 ions in total).
4. Fe(NO3)3: Fe(NO3)3 dissociates into 1 Fe^3+ ion and 3 NO3- ions (4 ions in total).
From the given options, NaF is likely to have the smallest freezing point depression because it produces the least number of ions when dissolved in water. However, without knowing the exact values of Kf for each solvent, we cannot definitively determine which solution will have the smallest freezing point depression.