LAB: MOLAR MASS DETERMINATION BY FREEZING POINT DEPRESSION

Question 1

A property that depends only upon the number of solute particles
(concentration), and NOT upon their identity (nature of the particles)

change in proportion to the conc of the solute particle

determining this allows us to determine the conc of a soln and calculate the molar masses of solutes

Answer 1

Colligative properties

Question 2

What are the 4 important colligative properties of solutions?

Answer 2

Vapor pressure lowering
Boiling point elevation and freezing point depression
Osmotic pressure

Question 3

is the pressure exerted by a vapor that is in dynamic equilibrium with its liquid (molecules are moving back and forth between liquid and vapor phases)

Answer 3

Vapor pressure

Question 4

The vapor pressure of a solvent in a solution is always lower than the vapor pressure of the pure solvent. The vapor pressure lowering is directly
proportional to the mole fraction of the solute.

Question 5

is defines as the boiling point of the soln (Tb) minus the boiling point of the pure solvent (Tnaughtb)

Answer 5

Boiling point elevation

Question 6

The boiling points of solutions are all higher than that of the pure solvent. Difference
between the boiling points of the pure solvent and the solution is proportional to the
concentration of the solute particles

Question 7

∆Tb is proportional to the VP lowering and proportional to the concentration of the
solution (molality)

Question 8

Because the presence of a non-volatile solute lowers the vapor pressure of a
solution, it must also affect the boiling point of the solution. Bp of salt solution is
greater than water.

Question 9

freezing point of the pure solvent minus the freezing point of the solution

Answer 9

Freezing point depression

Question 10

The freezing points of solutions are all lower than that of the pure solvent. The
freezing point depression is directly proportional to the molality of the solute.

Question 11

is a process through which a solvent flows through a semipermeable membrane
from a less concentrated solution to a more concentrated one

Answer 11

Osmosis

Question 12

is a selectively porous material; that is, it only allows certain
substances to pass through it.

Answer 12

Semipermeable membrane

Question 13

is the amount of pressure required to stop osmosis.

Answer 13

Osmotic pressure