1. Chemistry Notes Unit 7: P, V and ‘n’

2. (1) Pressure & Volume P = Pressure; V = Volume “Boyle’s Law”
Relationship: Inverse
Volume increases = Pressure decreases
Volume decreases = Pressure increases
*Temperature and ‘n’ constant
Equation: P1V1 = P2V2

3. (2) Pressure & Volume Graph

4. (3) PV Example #1
You have a gas in a closed container that occupies 50 mL and has a pressure of 2 atm. What would be the new pressure if the gas was compressed to a new volume of 30 mL? ______________________________________________
a. What are your knowns and unknowns? Circle the unknown and underline the knowns.
b. What is held constant?
c. What is the cause and effect (use “so”):
d. Calculate. Show all units. Once finished, check answer to see if it makes sense.
e. Draw pictures.

5. (4) PV Example #2
What would be the new volume of 150 cm3 of gas at 20oC and at a pressure of 760 mmHg were changed to a pressure of 500 mmHg? ________________________________________________
a. What are your knowns and unknowns? Circle the unknown and underline the knowns.
b. What is held constant?
c. What is the cause and effect (use “so”):
d. Calculate. Show all units. Once finished, check answer to see if it makes sense.
e. Draw pictures.

6. (5) PV Example #3
A closed syringe contains 3 “puffs” of air and has an initial volume of 20 cm3 and a pressure of 30 psi. Without changing the temperature, the volume is increased to 45 cm3. What is the new pressure? ________________________________________________
What are the knowns and unknowns?
What’s held constant?
What’s the cause and effect?
Calculate the new pressure. ________________________________________________
If 1 atm = 14.7 psi = 760 mmHg = kPa, and if 1 kPa = 1000 Pa, convert the new pressure to Pa.

7. (6) PV Example #4
A closed syringe has an initial volume of 40 mL and a pressure of 12 psi. Without changing the temperature, the pressure is decreased to 8 psi. What is the new volume in poop sq? ______________________________________________ Convert the final volume to Liters using factor labeling.

8. (7) Pressure & # of Particles
P = Pressure; n = # of Particles
Relationship: Linear
# of Particles increases = Pressure increases
# of Particles decreases = Pressure decreases
*Temperature and Volume constant
Equation: P1 / n1 = P2 / n2

9. (8) Pressure & ‘n’ Graph
Pressure n

10. (9) P/n Example #1
5.5 puffs of air have a pressure of 900 mmHg. What is the pressure when three puffs of air are removed? ______________________________________________

11. (10) P/n Example #2
A bicycle tire has a pressure of 30 psi and has 5 puffs of air in it. What is the new pressure when 1 extra puff of air is added to the tire? ______________________________________________