1. You will need a partner as well as a calculator
The Gas Laws
You will need a partner as well as a calculator

2. Ideal Gas Law
PV = nRT
Boyle’s Law
P1V1 = P2V2
Combined Gas Law
P1V1/T1 = P2V2/T2

3. Pressure
Pressure (P): The force of gas molecules as they hit the sides of the container in which they are placed.
 Units = Atmospheres (atm)
StandardTemperaturePressure = 1atm

4. Temperature StandardTemperaturePressure = 273 K
Temperature (T): Average kinetic energy.
The higher the energy, the higher the temperature.
Common units of temperature:
Kelvin (K): The ONLY units that can be used when doing numerical problems with gases.
*Degrees Celsius (0C): Must be converted to Kelvin before doing problems (by adding 273).
StandardTemperaturePressure = 273 K

5. Volume Volume (V): The amount of space in which a gas is enclosed.
The most commonly used unit of volume is liters (L).
Conversion: 1L = 1,000 mL

6. Which tank contains the greatest number of particles?
Number of particles = pressure x volume
10 atm
1 atm
40 atm
25 atm
30 L
60 L
45 L
15 L A B C D

7. Ideal Gas Law
Avogadro’s law: One mole of every gas has the same volume. (22.4 L)
STP = standard temperature & pressure
Standard temperature = 273 K
Standard pressure = 1 atm
All gases behave the same at the same temperature, volume and pressure.
H2O(g), CO2(g), O2

8. Ideal gas law: PV = nRT P = pressure (in atm) V = volume (L)
n = number of (moles) 
R = ideal gas constant L•atm/mol•K
T = temperature (Kelvin) = (oC + 273)

9. “We Do” PV = nRT
If I have 10 liters of a gas at a pressure of 1.5 atm and a temperature of 250 C, how many moles of gas do I have?
P = ___ atm
V = ___ L
n = ___ mol
R = (always this #) ______ atm L/mol K
T = __oC + (273) = ___ K

10. PV=nRT (P x V) = (n x R x T) 1.5 x 10 = n x 0.0821 x 298
Divide both sides by so “n” by itself
n = moles

11. “You Do”
If I have 23.5 moles of gas at a temperature of oC, and a volume of liters, what is the pressure of gas?
P =
V =
n =
R = (always this #)
T = ___oC+ (273) =

12. Boyle’s Law P1V1 = P2V2 P1 = First Pressure V1 = First Volume
P2 = Second Pressure
V2 = Second Volume
P and V are inversely proportional
(when one increases, the other decreases)

13. Boyles’ Law and Breathing
During an inhalation,
Lung volume increases.
the pressure in the lungs decreases.
air flows towards the lower pressure in the lungs.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

14. Boyles’ Law and Breathing
During an exhalation,
Lung volume decreases.
pressure within the lungs increases.
air flows from the higher pressure in the lungs to the outside.
Copyright © by Pearson Education, Inc.
Publishing as Benjamin Cummings

15. “We Do” P1V1 = P2V2
A high-altitude balloon contains L of He at 10.3 atm. What is the new volume when the balloon rises to an altitude where the pressure is only 2.3 atm?
P1 =
V1 =
P2 =
V2 =

16. P1V1 = P2V2
(10.3 atm) (30.0 L) = (2.3 atm) ( V2)

17. “You Do” P1V1 = P2V2
A gas with a volume of 4.02 L at a pressure of 2.31 atm is allowed to expand to L. What is the new pressure of the gas?
P1 =
V1 =
P2 =
V2 =

18. Combined Gas Law P1V1 = P2V2 T1 T2 P1 = First Pressure
****Remember that temperature needs to be in Kelvin (oC = 273K)****
P1 = First Pressure
V1 = First Volume
T1 = First Temperature
P2 = Second Pressure
V2 = Second Volume
T2 = Second Temperature

19. “We Do” P1V1/T1 = P2V2/T2
If I initially have a gas at a pressure of 1.3 atm, a volume of 24.6 liters and a temperature of 214K, and then I raise the volume to 46.0 L and increase the temperature to 286 K, what is the new pressure of the gas?
P1 = P2 =
V1 = V2 =
T1 = T2 =

20. P1V1/T1 = P2V2/T2 (1.5 atm)(24.6 L) = (P2)(46.0 L) 214 K 286 K
0.172 atm L/K = (P2) (0.161 atm/K)
P2 = 1.75 atm

21. “You Do” P1V1/T1 = P2V2/T2
If I have 23.5 L of gas held at STP, what is the volume of gas if I increase the pressure to 45.2 atm and increase the temperature to oC?
P1 = P2 =
V1 = V2 =
T1 = T2 =