Phases and Colligative Properties

Question 1

Define Vapor Pressure

Answer 1

pressure do to escaped molecules from liquid surface at a given temperature

Question 2

What affects vapour pressure of a liquid?

Answer 2

• temperature
• pressure
  ^ both indicated on phase diagram
• solute dissolved in the liquid

Question 3

Raoult’s Law

Answer 3

amount of solute dissolved in a liquid affects the vapor pressure of the liquid

Question 4

What is the common equation of pressure?

Answer 4

Pressure = Force / Area

Question 5

Does changing the amount of liquid in a container affect the vapor pressure? How so?

Answer 5

• No!
• Change amount of liquid = change volume
• as volume changes, surface area changes
• therefore pressure stays the same
• change in molecules exerting force proportional change in surface area

Question 6

What is the definition of boiling temperature?

Answer 6

vapour pressure of solution equals atmospheric pressure of surroundings

Question 7

If you dissolve more solute in a solution, what happens to vapor pressure according to ____ law.

Answer 7

increase solute = decrease vapor pressure

- Raoult’s law

Question 8

As vapor pressure changes, what happens to boiling point?

Answer 8

• decrease vapor pressure = increase boiling point

- more energy needed to be put into the system to reach equilibrium

Question 9

What is a non-volatile substance?

Answer 9

a substance that does not readily evaporate into a gas

Question 10

When adding solute to a pure solvent, what happens to freezing temperature?

Answer 10

( a decrease in vapour pressure due to addition of solute (Raoult’s))
- add solute
= decrease freezing point
- more solute to interfere with crystal lattice structure at freezing pt