1. Chemistry is “Real” gas
Gas Laws
Chemistry is “Real” gas

2. Pressure Pressure is force per unit area Standard atmospheric pressure
1 atmosphere
760 mm Hg = 760 torr
29.92 inches Hg
kPa
14.7 psi

3. Barometers
Mercury barometer

4. Manometers
Open arm
manometer

5. Manometers
Open arm
manometer

6. Manometers
Closed arm
manometer

7. Pressure Converting units Convert 728 torr into atmospheres.
728 torr x 1 atmosphere
760 torr
= atm
Convert 86 kPa into torr.
86 kPa x 760 torr
kPa
= 645 torr

8. Pressure and volume: Boyle’s Law
As pressure is increased, volume decreases by the same fraction (constant temperature)
P1V1 = P2V2
Find the new volume if the gas in a 4.5 mL syringe is compressed from 1.05 atm to 2.31 atm.

9. Boyle’s Law Make a list of variables P1 = 1.05 atm V1 = 4.5 mL
P2 = 2.31 atm V2 = V2
Plug variables into equation and solve for V atm x 4.5 mL = 2.31 atm x V2
2.31 atm atm
1.05 x 4.5 mL = V2
2.31
= 2.05 mL

10. Boyle’s Law
Freddie Krueger compresses air in a syringe from 5.1 mL to 1.9 mL. If the gas was initially at 101 kPa, what is the new pressure?
101 kPa x 5.1 mL = P2 x 1.9 mL
101 x 5.1kPa = P2
1.9
= 271 kPa

11. Boyle’s Law
Kinetic explanation of Boyle’s Law – when volume is decreased, particles of a gas have less room and strike the walls of the container more often.

12. Temperature and volume: Charles’ Law
As the temperature increases, the volume increases (constant pressure)
V1/T1 = V2/T2
(T must be in kelvins)
George of the Jungle has a syringe of nitrogen gas with volume 4.9 mL. The temperature of the jungle is 40ºC (313K). He places the syringe in a pot of boiling water (100ºC, 373K). What is the new volume?

13. Charles’ Law = List variables: V1 = 4.9mL T1 = 313K V2 = V2 T2 = 373K
Plug variables into Charles’ Law equation and solve for V2
4.9mL V2
313K K =

14. Charles’ Law = Solve for V2 4.9mL V2 313K 373K 4.9mLx373K = V2 313K

15. Charles’ Law
Jim Jones has a syringe full of hydrogen cyanide gas (9.4 mL) at 33ºC. He submerges it in dry ice/carbon tetrachloride and the volume goes down to 7.6 mL. What is the temperature of the dry ice/carbon tetrachloride?

16. Charles’ Law = = V1/T1 = V2/T2 9.4 mL 7.6 mL 306K T2 9.4 1
(306Kx7.6) T2
(306Kx7.6)/9.4 = T2
= 247K (-26ºC) = =

17. Charles’ Law
Kinetic explanation of Charles’ Law – as temperature increases, the particles move faster and hit the walls of the container harder, increasing the volume.
In a rigid container the pressure increases. (Gay-Lussac’s Law)

18. Combined Gas law Combination of Boyle’s and Charles’ Laws P1V1 = P2V2
T T2
The amount of gas remains constant.

19. Combined Gas Law
Jane compresses a sample of fluorine gas at standard pressure in a syringe from 6.2 mL to 2.3 mL. As she does this the temperature of the gas increases from 296K to 310K. What is the new pressure of the gas in atmospheres?

20. Combined Gas Law = = 1atm x 6.2 mL P2 x 2.3 mL 296K 310K
1 x 6.2 x P2
296 x 2.3
= 2.8 atm = =

21. Combined Gas Law
JJ leaves his basketball on the hot pavement on a summer afternoon. The pressure in the ball increases from 20.7 psi to 21.3 psi. The internal temperature of the ball went from 22ºC to 41ºC. If the original volume was 5.2 liters, what is the final volume?

22. Combined Gas Law P1V1 = P2V2 T1 T2 20.7psi x 5.2 L = 21.3psi x V2
295K K
20.7psi x 5.2 L x 314K = V2
295K x 21.3psi
= 5.4 L

23. Law of combining gas volumes
Under the same conditions, equal volumes of any gas contain the same number of particles (Avogadro’s principle)
Standard conditions – 0ºC (273K) and 1 atm
Under standard conditions, one mole of a gas occupies 22.4 liters (molar volume)

24. Law of combining gas volumes
In a reaction where all the reactants and products are gases, the mole ratios are also volume ratios
2H2 + O2  2H2O