The Gas Laws

1
The Gas Laws

• Section 11.2

2
Boyles Law Pressure and Volume

• A confined gas can be squeezed into a smaller
  volume.
• Robert Boyle (1627-1691), and English scientist,
  used a simple J tube apparatus to compress gases.

3
Boyles Law Pressure and Volume

• If the pressure of a gas increases, its volume
  decreases proportionally.
• If the pressure of a gas decreases, its volume
  increases proportionally.
• If the volume of a gas increases, its pressure
  decreases proportionally.
• If the volume of a gas decreases, its pressure
  increases proportionally.

4
Boyles Law Pressure and Volume

• Boyles Law the pressure and volume of a gas at
  constant temperature are inversely proportional.
• Mathematically Boyles Law is expressed as
• P1V1 P2V2

5
Boyles Law Pressure and Volume

• Sample Problem A sample of helium gas in a
  balloon is compressed from 4.0 L to 2.5 L at a
  constant temperature. If the pressure of the gas
  in the 4.0 L volume is 210 kPa. What will the
  pressure be at 2.5 L?
• P1V1 P2V2
• (210 kPa) (4.0 L) P2(2.5 L)
• P2 340 kPa

6
Homework

• Problems 6-11 pg 389

7
Charless Law Temp and Volume

• Jacques Charles (1746-1823)-French scientist, hot
  air balloon pioneer. Investigated how changing
  the temperature of a fixed amount of gas at
  constant pressure affected its volume.

8
Charles Law

• At constant pressure, the volume of a gas is
  directly proportional to its Kelvin temperature.
• Mathematically expressed as

9
Example Problem

• A gas sample is at 40.0 C and a volume of 2.32
  L. If the temperature is raised to 75.0 C ,
  what will the volume be, assuming the pressure
  remains constant?

10
Example Problem

• Convert Temps to Kelvin
• 40C 273 313K
• 75C 273 348K

11
Homework

• Problems 12 to 16 pg 393

12
Gay-Lussacs LawPressure and Temperature

• Joseph Louis Gay-Lussac (1778-1850) French
  scientist, In 1804 took a hot air balloon ride to
  7,000 meters. Not equaled for 50 years
• The pressure of fixed mass of gas varies directly
  with the Kelvin temperature when the volume
  remains constant.

13
Gay-Lussacs LawPressure and Temperature
14
Example Problems

• The pressure of a gas in a tank is 3.20 atm at
  22.0C. If the temperature rises to 60.0C, what
  will be the gas pressure in the tank?
• Convert to Kelvin
• T1 22.0C 273 295 K
• T2 60.0C 273 333 K

15
Example Problems

• Substitute Values
• P2 3.61 atm

16
The Combined Gas Law

• Boyles, Charless and Gay-Lussacs Laws can be
  combined into a single gas law.
• The amount of gas must be fixed.
• The combined gas law is

17
Example Problem

• A gas at 110 kPa and 30.0C fills a flexible
  container with an initial volume of 2.00 L. If
  the temperature is raised to 80.0C and the
  pressure is increased to 440 kPa, what is the new
  volume?