1. Lesson 5.3 – Gas Laws Chemistry 1 Honors Dr. J. Venables
Northwestern High School

2. Gas Laws Boyle’s Law: P and V, at constant T
Charles’ Law: V and T at constant P
Gay-Lussac’s Law: P and T at constant V
Combined Gas Law: P, V and T
Ideal Gas Law: Moles join the Party (Thanks Avogadro).

3. Boyles Law
At constant temperature, pressure and volume have an inverse relationship.
If one doubles the pressure, volume is reduced by half.
Relation shown in figure and graph below.
P1V1 = P2V2

4. Practice
1. A sample of Ar gas occupies a volume of 1.05 L at a pressure of 128 kPa. What is the pressure of the same gas sample if the volume is reduced to 0.79 L?
2. A sample of O2 gas occupies a volume of 225 mL at a pressure of 0.87 atm. What volume will the sample occupy at a pressure of 0.37 atm?

5. Charles Law Relates gas temperature and volume, at constant pressure.
As gas temperature increases, so does the volume.
As temp. increases, so does the kinetic energy of the particles, which strike the walls more frequently increasing the volume of the container held at constant pressure.
See Figure and graph below. Direct relationship between P and T.

6. Charles Law Formula Temperature must be in Kelvin for all gas laws.
TK = TC + 273
Absolute Zero is start of Kelvin Scale. Volume = 0. Kinetic Energy ceases.

7. Practice
1. A gas sample occupies 1.66 L at 257 K. What volume will it occupy at 395 K?
2. A gas sample occupies 75.8 mL at 25°C. At what temperature will the volume of the sample be mL?

8. Gay-Lussac’s Law Relates temperature to Pressure at constant V.
Same direct relationship as V and T.
Again, temperature must be in Kelvin as for all gas law problems.

9. Practice
A confined gas in a rigid container has a pressure of 855 kPa at 30°C. At what temperature will the pressure in the container reach 1500 kPa?