Not so long ago, in a chemistry lab far far away…May the FORCE/area be with you

Gas Laws: Gay-Lussac’s and

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

to:1. Describe Gay-Lussac’s Law with a formula2. Use Gay-Lussac’s Law to determine either

a temperature or volume3. Combine all three laws into the Combined

Gas Law4. Use the Combined Gas Law to determine

either temperature, volume or pressure

I’ll be needing this stuff because I’m in deep ____!!!!

Gay-Lussac’s Law

If n and V are constant, then P α T

P and T are directly proportional.

If one temperature goes up, the pressure goes up!

Joseph Louis Gay-Lussac (1778-1850)1 2

1 2

P PT T

Gay Lussac’s Law SummaryThe pressure and temperature of a gas are directly related, provided that the volume remains constant.

1 2

1 2

P PT T

Example, Page 25:1

P1

T1

P2

T2

3.00 atm

298 K

P2

325 K

3.3 atm

Gay-Lussac’s Law Practice, Page 25:2

P1

T1

P2

T2

1.8 atm

293 K

1.9 atm

T2

310 K or 36 oC

Most Caring Person!!

Teacher Debbie Moon's first graders were discussing a picture of a family. One little boy in the picture had a different hair color than the other members.. One of her students suggested that he was adopted. A little girl said, "I know all about adoption, I was adopted..“"What does it mean to be adopted?" asked another child."It means", said the girl, "that you grew inyour mommy's heart instead of her tummy!"

Now let’s put all 3 laws together into one big law…….

Combined Gas Law

The good news is that you don’t have to remember all three gas laws! Since they are all related to each other, we can combine them into a single equation. BE SURE YOU KNOW THIS EQUATION!

No, it’s not related to R2D2

1 1 2 2

1 2

PV PVT T

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

1 1 2 2

1 2

PV PVT 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

Greatest Reasons for Termination from a Job

1. The inability to get along with co-workers and supervisors.

2. Absenteeism

3. Lack of interest

4. Continuously making costly mistakes

5. Does not follow directions

6. Shows an unwillingness to learn

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 TableP1 = 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

15 Helpful Hints On The Lab Report from

Mr. T’s Vast Lab Experience!!!

Hint #5. A record of data is essential. It fools the instructor into thinking that you were working.

Gas Laws: Gay-Lussac’s and

CombinedLet’s see if you can:

1. Describe Gay-Lussac’s Law with a formula.2. Use Gay-Lussac’s Law to determine either

a temperature or volume3. Combine all three laws into the Combined

Gas Law4. 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

Mixed Problems: Page 28:1

Boyle’s Law

P1 V1 P2 V2

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

1,242,000 Pa

Try This One, Page 28:8Charles’ Law

V1

T1

V2

T2

31.4 L

296.6 K

25.0 L

T2

236 K or -37 oC

Combined Gas Law Problems: Page

29:1 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

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. -124oC2. 149oC3. 119oC4. -154oC5. 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

The End!!!