1/17/2024 VAPOR PRESSURE

Question 1

What is vapor pressure?

Answer 1

• THE TENDENCY OF A LIQUID TO BECOME A GAS
  (the pressure exhibited by vapor present above a liquid surface)
• THE VAPOR PRESSURE IS A PROPERTY OF A CHEMICAL
  (it won’t change based on container)

The exerted pressure on the vessel is equal to the vapor pressure

Question 2

What are substances with relatively high vapor pressures called?

Answer 2

VOLATILE

(volatile liquids have a lower boiling point than non-volatile liquids)

Question 3

What factors affect vapor pressure (Pvap)?

Answer 3

Intermolecular Forces:
- stronger/higher intermolecular forces = lower Pvap

Temperature:
- higher T increases average particle speed = higher Pvap

• NOT surface area
• greater surface area increases evaporation rate, but does not affect vapor pressure

Question 4

What are all of the intermolecular forces (strongest to weakest)

Answer 4

H-Bonds
Covalent
Ionic
Dipoles
Dispersion Forces
Van Der Waals

Question 5

When do liquids boil?

Answer 5

Liquids boil when the vapor pressure equals the external pressure
(when Pvap = Pext)

• The boiling point of a liquid can change based on different external pressures (ex: utah vs. california)

Question 6

What is the vapor pressure of water at 100 degrees celsius?

Answer 6

760 torr

Question 7

What is Raoult’s Law?

Answer 7

The total vapor pressure of an ideal solution depends on the vapor pressure and mole fraction of each component in the solution

• Case 1: everything is volatile and you’ll use Raoult’s Law to add everything up
• Case 2: solutes aren’t volatile, so they don’t contribute to overall Pvap

Question 8

Does the solubility of a gas in water increase or decrease as temperature increases?

Answer 8

Solubility of gases in water DECREASES with increase in temperature
(particles want to escape water in higher temperature)

Question 9

What are deviations from Raoult’s Law?

Answer 9

When a compound experiences fewer or more intermolecular forces when in a mixture vs. pure