Vapor Pressure

Question 1

Phase changes are reversible and reach equilibrium in what type of container?

Answer 1

Closed container

Question 2

What is vapor pressure?

Answer 2

The pressure exerted by a vapor on a liquid at gas-liquid equilibrium in a closed system

Question 3

As temperature increases, does vapor pressure increase or decrease?

Answer 3

It increases

Question 4

As the strength of intermolecular forces increases, does vapor pressure increase or decrease?

Answer 4

It decreases

Question 5

Does a high boiling point indicate a high or low vapor pressure?

Answer 5

Low vapor pressure

Question 6

When boiling point is high, are intermolecular forces weak or strong?

Answer 6

Strong. This causes lower vapor pressure.

Question 7

What is the Clausius-Clapeyron equation?

Answer 7

ln(P) = (-ΔHvap)/R * (1/T) + C
P = vapor pressure
R = 8.314 J/mol*K
T = temp in K
C = constant

Question 8

Given the slope of the graph of ln(P) vs 1/T, how to you find ΔHvap?

Answer 8

ΔHvap = -slope * R
R = 8.314 J/mol*K

Question 9

What is the two-point form of the Clausius-Clapeyron equation?

Answer 9

ln(P2/P1) = (-ΔHvap)/R * (1/T2 - 1/T1)
P = vapor pressure
R = 8.314 J/mol*K
T = temp in K

Question 10

The temperature at which vapor pressure equals external pressure is called what?

Answer 10

Boiling point
If external pressure is atmospheric pressure, it is the temperature where vapor pressure is 760 torr.

Question 11

What is normal boiling point?

Answer 11

Boiling point at 1 atm

Question 12

What is a volatile substance?

Answer 12

One that escapes to the gas phase at a lower temperature

Question 13

Do volatile substances have higher or lower vapor pressures?

Answer 13

Higher

Question 14

Does a low temperature and high pressure favor a solid, liquid, or gas?

Answer 14

Solid

Question 15

Does a high temperature and low pressure favor a solid, liquid, or gas?

Answer 15

Gas

Question 16

On a phase diagram, what does a triple point represent?

Answer 16

Where solid, liquid, and gas phases are in equilibrium

Question 17

On a phase diagram, what does the critical point represent?

Answer 17

The temperature and pressure conditions where a supercritical fluid exists (gas and liquid properties).

Question 18

High ΔHvap means a high or low vapor pressure?

Answer 18

Low vapor pressure

Question 19

A high boiling point means a high or low ΔHvap?

Answer 19

High ΔHvap

Question 20

Why do high temperatures and weak intermolecular forces cause high vapor pressure?

Answer 20

These conditions cause more liquid molecules to enter the gas phase