Question

When of alanine are dissolved in of a certain mystery liquid , the freezing point of the solution is lower than the freezing point of pure . On the other hand, when of iron(III) nitrate are dissolved in the same mass of , the freezing point of the solution is lower than the freezing point of pure . Calculate the van't Hoff factor for iron(III) nitrate in . Be sure your answer has a unit symbol, if necessary, and round your answer to significant digits.

Answer 1

Answer:

i = 3,5

Explanation:

There are missing the following values:

132 g Alanine

1150g of X

4,4°C the first freezing point dercreasing

132g of Iron(III) nitrate

5,6°C the second freezing point decreasing.

The freezing point depression is a colligative property that describes the decrease of the freezing point of a solvent on the addition of a non-volatile solute.

The formula is:

ΔT = i kf mb

Where ΔT is freezing point decreasing, i is Van't Hoff factor, kf, is cryoscopic constant and mb is molality of solution.

For alanine Van't Hoff factor is 1 (Ratio between particles in dissolution and before dissolution), molality is:

132g×(1mol/89,09g) = 1,48mol / 1,150kg = 1,29 mol/kg

Replacing:

4,4K = 1 kf 1,29mol/kg

kf = 3,41 K·kg/mol

Now, for Iron(III) nitrate molality is:

132g×(1mol/241,86g) = 0,546mol / 1,150kg = 0,475 mol/kg

Replacing:

5,6K = i×3,41 K·kg/mol×0,475 mol/kg

i = 3,5

I hope it helps!