1. Ch Gases
I. Physical Properties

2. A. Kinetic Molecular Theory
Particles in an ideal gas…
have no volume.
have elastic collisions.
are in constant, random, straight-line motion.
don’t attract or repel each other.
have an avg. KE directly related to Kelvin temperature.

3. B. Real Gases Particles in a REAL gas… have their own volume
attract each other
Gas behavior is most ideal…
at low pressures
at high temperatures
in nonpolar atoms/molecules

4. C. Characteristics of Gases
Gases expand to fill any container.
random motion, no attraction
Gases are fluids (like liquids).
no attraction
Gases have very low densities.
no volume = lots of empty space

5. C. Characteristics of Gases
Gases can be compressed.
no volume = lots of empty space
Gases undergo diffusion & effusion.
random motion

6. D. Temperature
Always use absolute temperature (Kelvin) when working with gases. ºF ºC K
-459 32
212
-273
100
273
373
K = ºC + 273

7. E. Pressure
Which shoes create the most pressure?

8. E. Pressure Barometer measures atmospheric pressure Aneroid Barometer
Mercury Barometer
Aneroid Barometer

9. E. Pressure Manometer measures contained gas pressure U-tube Manometer
Bourdon-tube gauge

10. E. Pressure KEY UNITS AT SEA LEVEL 101.325 kPa (kilopascal) 1 atm
760 mm Hg
760 torr
14.7 psi

11. Standard Temperature & Pressure
F. STP
STP
Standard Temperature & Pressure
0°C K
1 atm kPa
-OR-

12. II. The Gas Laws BOYLES CHARLES GAY-LUSSAC
Ch Gases
II. The Gas Laws BOYLES CHARLES GAY-LUSSAC P V T

13. A. Boyle’s Law P V
PV = k

14. A. Boyle’s Law
The pressure and volume of a gas are inversely related
at constant mass & temp P V
PV = k

15. A. Boyle’s Law

16. B. Charles’ Law V T

17. B. Charles’ Law
The volume and absolute temperature (K) of a gas are directly related
at constant mass & pressure V T

18. B. Charles’ Law

19. C. Gay-Lussac’s Law P T

20. C. Gay-Lussac’s Law
The pressure and absolute temperature (K) of a gas are directly related
at constant mass & volume P T

21. D. Combined Gas Law T PV
= k
P1V1 T1 =
P2V2 T2

22. E. Gas Law Problems
A gas occupies 473 cm3 at 36°C. Find its volume at 94°C.
CHARLES’ LAW
GIVEN:
V1 = 473 cm3
T1 = 36°C = 309K
V2 = ?
T2 = 94°C = 367K T V
WORK:
P1V1T2 = P2V2T1
(473 cm3)(367 K)=V2(309 K)
V2 = 562 cm3

23. E. Gas Law Problems
A gas occupies 100. mL at kPa. Find its volume at 200. kPa.
BOYLE’S LAW
GIVEN:
V1 = 100. mL
P1 = 150. kPa
V2 = ?
P2 = 200. kPa P V
WORK:
P1V1T2 = P2V2T1
(150.kPa)(100.mL)=(200.kPa)V2
V2 = 75.0 mL

24. E. Gas Law Problems COMBINED GAS LAW P T V V1 = 7.84 cm3
A gas occupies 7.84 cm3 at 71.8 kPa & 25°C. Find its volume at STP.
COMBINED GAS LAW
GIVEN:
V1 = 7.84 cm3
P1 = 71.8 kPa
T1 = 25°C = 298 K
V2 = ?
P2 = kPa
T2 = 273 K
P T V
WORK:
P1V1T2 = P2V2T1
(71.8 kPa)(7.84 cm3)(273 K)
=( kPa) V2 (298 K)
V2 = 5.09 cm3

25. E. Gas Law Problems
A gas’ pressure is 765 torr at 23°C. At what temperature will the pressure be 560. torr?
GAY-LUSSAC’S LAW
GIVEN:
P1 = 765 torr
T1 = 23°C = 296K
P2 = 560. torr
T2 = ? P T
WORK:
P1V1T2 = P2V2T1
(765 torr)T2 = (560. torr)(309K)
T2 = 226 K = -47°C

26. Ch. 10 & 11 - Gases
III. Ideal Gas Law (p , )

27. A. Avogadro’s Principle

28. A. Avogadro’s Principle
Equal volumes of gases contain equal numbers of moles
at constant temp & pressure
true for any gas V n

29. UNIVERSAL GAS CONSTANT
B. Ideal Gas Law PV nT V n PV T
= k
= R
UNIVERSAL GAS CONSTANT
R= Latm/molK
R=8.315 dm3kPa/molK

30. UNIVERSAL GAS CONSTANT
B. Ideal Gas Law
PV=nRT
UNIVERSAL GAS CONSTANT
R= Latm/molK
R=8.315 dm3kPa/molK

31. B. Ideal Gas Law IDEAL GAS LAW P = ? atm n = 0.412 mol
Calculate the pressure in atmospheres of mol of He at 16°C & occupying L.
IDEAL GAS LAW
GIVEN:
P = ? atm
n = mol
T = 16°C = 289 K
V = 3.25 L
R = Latm/molK
WORK:
PV = nRT
P(3.25)=(0.412)(0.0821)(289)
L mol Latm/molK K
P = 3.01 atm

32. B. Ideal Gas Law IDEAL GAS LAW V = ? n = 85 g T = 25°C = 298 K
Find the volume of 85 g of O2 at 25°C and kPa.
IDEAL GAS LAW
GIVEN:
V = ?
n = 85 g
T = 25°C = 298 K
P = kPa
R = dm3kPa/molK
WORK:
85 g 1 mol = 2.7 mol
32.00 g
= 2.7 mol
PV = nRT
(104.5)V=(2.7) (8.315) (298)
kPa mol dm3kPa/molK K
V = 64 dm3