1. The Gas Laws

2. Direct vs Indirect Relationships
Directly proportional - as one variable goes up/down the other goes up/down as well.
Both variables do the same thing.
Indirectly proportional - as one variable goes up/down the other goes down/up.
The two variables do the opposite thing.

3. Apparatus for Studying the Relationship Between
Pressure and Volume of a Gas
As P (h) increases
V decreases

4. Boyle’s Law P1 x V1 = P2 x V2 (temperature remains constant)
Pressure (P) and
Volume(V) are _________
proportional
indirectly

5. Example 1
A helium balloon was compressed from 4.0L to 2.5L at a constant temperature. If the pressure of the gas in the 4.0L balloon is 210 kPA, what will the pressure be at 2.5L?
V1 = 4.0L
V2 = 2.5L
P1= 210 kPa
P2 = ?
P1V1 = P2V2
(210 kPa) × (4.0L) = P2 × (2.5L)
P2 = 336 kPa ≈ 340 kPa

6. Example 2
A sample of neon gas occupies 0.200L at atm. What will be its volume at 29.2 kPa pressure?
P1V1 = P2V2
Given:
V1 = 0.200L V2 = ?
P1= atm P2 = 29.2 kPa
(87.1 kPa) × (0.200L) = (29.2 kPa) × V2
V2 = 0.597L
**Units must match for each variable (doesn’t matter which one is converted)
0.860 atm kPa
1 atm
= 87.1 kPa

7. Charles’s Law V1 V2 T1 T2 Pressure is constant
Temperature must be in Kelvin
Volume (V) and temperature (T) are directly proportional =

8. Example 1
A gas sample at 40.0°C occupies a volume of 2.32L. If the temperature is raised to 75.0°C, what will the volume be, assuming the pressure remains constant?
Given:
T1 = 40.0°C = 313K T2 = 75.0°C = 348K
V1= 2.32L V2 = ?
V V2
T T2 =
2.32L V2 =
V2 = 2.58L

9. Example 2
A gas sample at 55.0°C occupies a volume of 3.50L. At what new temperature in Celsius will the volume increase to 8.00L?
Given:
T1 = 55.0°C = 328K T2 = ?
V1= 3.50L V2 = 8.00L
V V2
T T2 =
3.50L T2 =
T2 = 750.K -273 = 477°C

10. Gay-Lussac’s Law P1 P2 T1 T2 Volume is constant
Temperature must be in Kelvin
Pressure (P) and temperature (T) are directly proportional =

11. Example 1
The pressure of a gas in a tank is 3.20 atm at 22.0°C. If the temperature rises to 60.0°C, what will be the gas pressure in the tank?
Given:
P1 = 3.20 atm P2 = ?
T1= 22.0°C = 295K T2 = 60.0°C =333K
P P2
T T2 =
3.20 atm P2
295K K =
P2 = 3.61 atm

12. Example 2
A rigid container has a gas at constant volume at 665 torr pressure when the temperature is 22.0°C. What will the pressure be if the temperature is raised to 44.6°C?
Given:
P1 = 665 torr P2 = ?
T1= 22.0°C = 295K T2 = 44.6°C =317.6K
P P2
T T2 =
665 torr P2
295K K =
P2 = 716 torr