What is the solution's freezing point depression?

Answer 1

To solve freezing point depression problems, you need to know the following things:

-- the identity of the solute (the thing you are adding to the liquid)
-- the identity of the solvent (the liquid)
-- whether the solute is molecular or ionic, and if ionic, how many ions it forms
-- the amount of solute (in grams or moles)
-- the amount of solvent (in kilograms)
-- the value of Kf of the solvent (for water, it is -1.858 K·kg/mol (or -1.858 °C molal-1)
Then you use the following equation:
∆T = i * Kf * m

where ∆T is the change in the freezing point, "i" is the number of molecules or ions formed upon addition to the solvent, Kf is the freezing point depression constant, and "m" is the molality of the solution.
The Kf of water for a freezing point depression is known and is equal to -1.858 °C·kg/mol (or -1.858 °C molal-1)
The value of "i" has to do with what you add to the water. If you added sugar, a molecular compound the value of "i" is 1.0. If you add a ionic compound like NaCl, the value of "i" is 2.0 because for every 1 molecule of NaCl, you make 2 ions: one Na+ and one Cl- in water. For MgCl2, the value of "i" is thus 3.0 (for each MgCl2 you get one Mg2+ and two Cl- ions, so a total of 3 ions).
To find "m," the molality of a solution you need to know the number of moles of solute and the number of kilograms of solvent (m = moles/kg). If you are given the number of grams of solute, the number of moles is found from the mass and the molar mass of the solute.
grams of solute ÷ molar mass of solute = moles of solute
To find the molality, just divide the moles of solute by the kilograms of solvent moles of solute ÷ kilograms solvent = molality Note: If you are given the volume of the solvent instead of the mass, use the density of the solvent to convert -- the density of water is 1 kilogram per liter)
Liters of solvent * density of solvent = kilograms of solvent
Now just plug all the numbers into the equation at the top of the answer!

Answer 2

The freezing point depression is the difference between the freezing point of a pure solvent and that of a solution. It is calculated by the formula ΔTf = i * Kf * m, where ΔTf is the freezing point depression, i is the van't Hoff factor, Kf is the cryoscopic constant, and m is the molality of the solute.

Answer 3

You must know the freezing point of the pure substance first. Freezing point depression happens when you have a substance with impurities (the amount and type of the impurities determines the change in freezing point). So once you have your recorded freezing point of your slightly impure substance (the FP that you measure), subtract that from the literature value for the freezing point of the pure substance (this can be found online for your particular substance), and there you have your depression.

(Freezing point of a solution)=(freezing point of the pure substance) - (freezing point depression.

Answer 4

The solvent used in the solution, the concentration used in the solution and the number of ions produced in the solution will affect the freezing point depression and the boiling point elevation of a solution.

Answer 5

When you add a salt to a solution, it does a number of things. The most prominent things are that it first raises the boiling point, and lowers the freezing point. This is why they use salts on roads. While it does not melt the ice, it does prevent any more ice from freezing, or at least makes it reach a lower temperature first. hope this helped!

Answer 6

Will a 0.5 M solution have a higher freezing point than a 0.75 M solution of the same substance?

Answer 7

triangle T little f is the difference in temperature between its freezing point of its pure solvent.

Answer 8

Ur so cold... U just don't even wanna live anymore

Answer 9

See this link for the formula.

Answer 10

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