1. What is the freezing point depression of the benzoic/lauric acid solution? 2.

Question

1. What is the freezing point depression of the benzoic/lauric acid solution?

2. What is the Molal concentration of benzoic/lauric acid solution?

3. Amount of Benzoic acid solute

4. Molar mass of benzoic acid(experimental value)

5. Molar mass of benzoic acid(expected value)

6. Molar mass percent difference

There is 7.78 grams of lauric acid in the mixture and 1.14 grams of benzoic acid in the mixture.

freezing point of pure lauric acid is 43.7 degrees celcius

freezing point of benzoic/lauric acid mixture is 37.1 degrees celcius

The molal freezing point depression constant of lauric acid has been determined Kf=3.9 degrrees celcius.

Explanation / Answer

1.
Depression in freezing point = 43.7 - 37.1 = 6.6 degree celsius

2.
use:
Depression in freezing point = Kf * m
6.6 = 3.9 * (m)
m = 1.78 molal
Answer: 1.78 molal

3.
mass of solute (benzoic acid) = 1.14 gm
Amount og benzoic acid = 1.14 gm

4.
mass of solute (benzoic acid) = 1.14 gm
molar mass of solute be x gm
number of moles of solute = mass /molar mass = 1.14/x
Mass of solvent(lauric acid) = 7.78 gm = 0.00778 Kg
use:
m = number of moles of solute / mass of solvent in Kg
1.78 = (1.14/x) / (0.00778)
0.01385= 1.14/x
x = 82.32 gm
Molar mass of benzoic acid(experimental value) = 82.32 gm

5.
benzoic acid is C6H5COOH
Molar mass = (12*6+5*1+12+2*16+1) = 122gm
Molar mass of benzoic acid(expected value) = 122 gm

6.
Mass difference = 122 gm - 82.32 gm = 39.7 gm

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.