1. NOTEBOOKS PINK PACKETS WHITE UNIT 7 PACKETS CALCULATORS

2. UNIT 7
Gas Laws
ABClark-Grubb

3. Elements that exist as gases at STP

4. Review of Physical Characteristics of Gases
Gases assume the volume and shape of their containers.
Gases are the most compressible state of matter.
Gases will mix evenly and completely when confined to the same container.
Gases have much lower densities than liquids and solids.

5. Important Measurements…
Symbol
Units
Pressure P
atm or kPa or mmHg
Volume V
L or mL or cm3
Temperature T
K (K = ºC + 273)
Amount n
moles
Gas Constant R
L · atm or L · kPa
mol · K mol · K

6. PRESSURE AND VOLUME ARE INVERSELY RELATEDh
Boyle’s Law:
At Constant temperature (T) &
Constant amount of gas (n)
PRESSURE AND VOLUME ARE INVERSELY RELATEDh
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7. T1 & T2 do not change due to CONSTANT TEMPERATURE
A sample of chlorine gas occupies a volume of 946 mL at a pressure of 726 mmHg.
What is the pressure of the gas (in mmHg) if the volume is reduced at constant temperature to 154 mL? V1 P1 P2 V2
P1 V1 T2 = P2 V2 T1
T1 & T2 do not change due to CONSTANT TEMPERATURE
726 mmHg x 946 mL = P2 x
154 mL
4460 mmHg = P2
Boyle’s Law

8. T1 & T2 do not change due to CONSTANT TEMPERATURE
A sample of bromine gas occupies a volume of 648 mL at a pressure of 1.23 atm.
What is the volume of the gas (in mL) if the pressure is reduced at constant temperature to standard pressure? V1 P1 V2 P2
1.00 atm
P1 V1 T2 = P2 V2 T1
T1 & T2 do not change due to CONSTANT TEMPERATURE
Find the standard pressure on the chart with the same unit as the given pressure and use it in the problem for P2.
1.23 atm
x 648 mL =
1.00 atm x V2
797 mL = V2
Boyle’s Law

9. NOTEBOOKS PINK PACKETS WHITE UNIT 7 PACKETS CALCULATORS

10. Charles’s Law At constant Pressure and Amount of gas
TEMPERATURE AND VOLUME ARE DIRECTLY RELATEDhttp://

11. P1 V1 T2 = P2 V2 T1 *Temperature must always be in Kelvin*
A sample of CO gas occupies 3.20 L at 125°C.
At what temperature will the gas occupy a volume of 1.54 L if the pressure remains constant?
398 K T2 V2
P1 & P2 do not change due to CONSTANT PRESSURE
*Temperature must always be in Kelvin*
T1 = 125°C = 398 K
P1 V1 T2 = P2 V2 T1
(3.20 L) T2 =
1.54 L
(398 K) T2
= 192 K
Charles’s Law

12. P1 & P2 do not change due to CONSTANT PRESSURE
A sample of CO2 gas occupies 6.91 L at 112°C.
What volume will the gas occupy when the temp. is raised to 179°C if the pressure remains constant?
385 K V2 V1 T2
452 K
P1 & P2 do not change due to CONSTANT PRESSURE
T1 = 112°C = 385 K
T2 = 179°C = 452 K
P1 V1 T2 = P2 V2 T1
6.91 L
(452 K) = V2
(385 K)
8.11 L = V2
Charles’s Law

13. NOTEBOOKS PINK PACKETS WHITE UNIT 7 PACKETS CALCULATORS

14. P1 V1 T2 = P2 V2 T1 Combined Gas Law (0.581 atm)(405mL)( 273K) =
If the initial volume of a gas was 405 mL at 90.0°C & atm, what would the volume be at STP? P1 V2 P2 T2
T1 = K = 363 K
T2 = 273 K
P2 = 1.00 atm
P1 V1 T2 = P2 V2 T1
(0.581 atm)(405mL)(
273K) =
(1.00 atm) V2
(363K)
177 mL = V2

15. P1 V1 T2 = P2 V2 T1 Combined Gas Law (1.25 atm)(236mL)( 298K) = P2
The initial volume of SO2 was 236 L at 75.0°C & 1.25 atm, what would the pressure be when the volume is raised to 652 L while the temp. is decreased to 25.0°C? P2 V2 T2
T1 = K = 348 K
T2 = K = 298 K
P1 V1 T2 = P2 V2 T1
(1.25 atm)(236mL)(
298K) = P2
(652L)
(348K)
0.387 atm = P2

16. NOTEBOOKS PINK PACKETS WHITE UNIT 7 PACKETS CALCULATORS

17. Ideal Gas Law
With the combined gas law, you use three variables: pressure, volume & temperature.
It assumes that the amount of gas is constant.
The Ideal Gas Law is used to calculate the number of moles of gas
The Ideal Gas Law uses a constant in it’s formula. (R)

18. Ideal Gas Law PV = nRT V = 30.5 L 1.00 atm x V =
Remember: n = moles!
Change the grams when you need to! n V T P
What is the volume (in liters) occupied by 49.8 g of HCl at STP?
49.8 g HCl
1 mole HCl
=1.36 mole
36.5 g HCl
T = 273 K
P = 1.00 atm
PV = nRT
R = L•atm/mol•K
1.36 mol x x 273 K
L•atm
mol•K
1.00 atm x V =
V = 30.5 L

19. Ideal Gas Law PV = nRT P = 8.28 atm P x 2.50L =
Remember: n = moles!
Change the grams when you need to! T P n
What is the pressure occupied by 28.0 g of O2 at 15.0°C & 2.50 L?
What is the pressure occupied by 28.0 g of O2 at 15.0°C & 2.50 L? V
1 mole O2
28.0 g O2
= mole
32.0 g O2
T = = 288 K
PV = nRT
R = L•atm/mol•K
0.875 mol x x 288 K
L•atm
mol•K
P x 2.50L =
P = 8.28 atm

20. Ideal Gas Law
With the combined gas law, you use three variables: pressure, volume & temperature.
It assumes that the amount of gas is constant.
The Ideal Gas Law is used to calculate the number of moles of gas
The Ideal Gas Law uses a constant in it’s formula. (R)