episode i attack of the gas

Not so long ago, in a chemistry lab far far away…

May the FORCE/area be with you

Gas Laws: CombinedAt the conclusion of our time together, you should be able

to:

1. Combine all three laws into the Combined Gas Law

2. Use the Combined Gas Law to determine either temperature, volume or pressure

The Combined Gas Law

The combined gas law expresses the relationship between pressure, volume and temperature of a fixed amount of gas.

1 1 2 2

1 2

PV PV

T T

Boyle’s law, Gay-Lussac’s law, and Charles’ law are all derived from this by holding a variable constant.

Combined Gas Law

If you should only need one of the other gas laws, you can cover up the item that is constant and you will get that gas law!

= P1 V1

T1

P2 V2

T2

Boyle’s Law

Charles’ Law

Gay-Lussac’s Law

Let’s Review: Mixed Problems: #1, Page 6

Boyle’s Law

P1 V1 P2 V2

(34,470 Pa) (473.18 mL) P2(13.13 mL)

1,242,000 Pa

Try This One #8, Page 7

Charles’ Law

V1

T1

V2

T2

31.4 L

296.6 K

25.0 L

T2

236 K or -37 oC

Combined Gas Law Problem

A sample of helium gas has a volume of 0.180 L, a pressure of 0.800 atm and a temperature of 29°C. What is the new temperature(°C) of the gas at a volume of 90.0 mL and a pressure of 3.20 atm?

Set up Data Table

P1 = 0.800 atm V1 = 180 mL T1 = 302 K

P2 = 3.20 atm V2 = 90 mL T2 = ??

Calculation

P1 = 0.800 atm V1 = 180 mL T1 = 302 K

P2 = 3.20 atm V2 = 90 mL T2 = ??

P1 V1 P2 V2

= P1 V1 T2 = P2 V2 T1

T1 T2

T2 = 3.20 atm x 90.0 mL x 302 K

0.800 atm x 180.0 mL

T2 = 604 K - 273 = 331 °C

= 604 K

Gas Laws: Gay-Lussac’s and

CombinedLet’s see if you can:

1. Combine all three laws into the Combined Gas Law

2. Use the Combined Gas Law to determine either temperature, volume or pressure

Learning Check

A gas has a volume of 675 mL at 35°C and 0.850 atm pressure. What is the temperature in °C when the gas has a volume of 0.315 L and a pressure of 802 mm Hg?

Calculation

P1 = 0.850 atm V1 = 675 mL T1 = 308 K

P2 = 1.06 atm V2 = 315 mL T2 = ??

P1 V1 P2 V2

= P1 V1 T2 = P2 V2 T1

T1 T2

T2 = 1.06 atm x 315 mL x 308 K

0.850 atm x 675 mL

T2 = 179 K - 273 = -94 °C

= 179 K

Pass the Clicker!!!

What will the new pressure (in atm) be if oxygen gas at room temperature (25.0 oC) and 1.00 atm is heated to 50.0 oC in a fixed container?

1. 2.00 atm2. 0.500 atm3. 1.08 atm4. 0.923 atm5. Not listed

A sample of neon gas occupies 266 mL at 25.5oC. At what temperature would the volume of this sample of gas be reduced to half its initial size? (1 atm = 101.325 kPa)

1. -124oC

2. 149oC

3. 119oC

4. -154oC

5. Not listed

What is the volume of CO2 at STP if the

original sample of CO2 had a volume of 65.0

mL at 95.0 mm Hg and 50.0oC?

1. .00687 mL2. 44.4 mL3. 6.87 mL4. 5220 mL5. Not listed

Combined Gas Law Problems: #1

P1 = 12.0 atm V1 = 23.0 L T1 = 200. K

P2 = 14.0 atm V2 = ? L T2 = 300. K

P1 V1 P2 V2

= P1 V1 T2 = P2 V2 T1

T1 T2

V2 = 12.0 atm x 23.0 L x 300 K

14.0 atm x 200 K

= 29.6 L

The End!!!