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Warmup A 40.0m 3 weather balloon at standard temperature encounters a sudden icy cool breeze during its journey into the Alaskan sky. If the weather balloon.

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Presentation on theme: "Warmup A 40.0m 3 weather balloon at standard temperature encounters a sudden icy cool breeze during its journey into the Alaskan sky. If the weather balloon."— Presentation transcript:

1 Warmup A 40.0m 3 weather balloon at standard temperature encounters a sudden icy cool breeze during its journey into the Alaskan sky. If the weather balloon decreases to 37.9 m 3, calculate the temperature of the icy cool breeze. Assume pressure is held constant at 610 mmHg.

2 The Combined Gas Law and Dalton’s Law of Partial Pressures You have all the sample problems in your packet

3 P 1 V 1 = P 2 V 2 T 1 T 2 (101.3 kPa)(V 1 )=(99.0 kPa) (466 ml ) (273K) (-4.6°C+273) (101.3kPa)(V 1 )(268.4°K)=(99.0 kPa)(466 ml)(273K) (101.3 kPa)(268.4K) (101.3 kPa)(268.4K) V 1 = 460ml Ex1. A half-full water bottle (at STP) travels by car and is put in a freezer high up in the mountains, changing the temperature to -4.6° C. The volume changes to 466 ml and the pressure decreases to 99.0 kPa. What was the original volume of the gas inside the water bottle?

4 Ex 2: A helium balloon at standard, constant temperature is placed in a vacuum, decreasing the pressure to 0.843 atm. The volume expands from 1.78 L to 4.98 L. What was the pressure of the balloon in the beginning? Use Boyle’s Law Use Combined Gas Law same answer…. I swear!

5 P 1 V 1 = P 2 V 2 T 1 T 2 P 1 (1.78 L)=(0.843 atm) (4.98 L) (273K) (273K) P 1 (1.78 L) (273K) =(0.843 atm)(4.98 L)(273K) (1.78 L) (273K) (1.78 L) (273K) P 1 = 2.36 atm

6 Ex 3: A helium-filled balloon has a volume of 50.0 L at 25°C and 1.08 atm. What volume will it have at 0.855 atm and 10.°C? InitialAfter P 1 =P 2 = V 1 =V 2 = T 1 =T 2 = P1P1 T1T1 P2P2 T2T2 1.08 atm 0.855 atm 50.0 L? 25°C 298 K 10.°C 283 K V 2 = V 2 = 60. L V1V1 V2V2

7 He CO 2 H2OH2O 0.7 atm 0.8 atm 2.3 atm Dalton’s Law of Partial Pressures the total pressure of a mixture of gases is equal to the sum of the partial pressures of the individual gases P total = P 1 + P 2 + P 3 + …

8 Ex 1: A container holds three gases: oxygen, carbon dioxide, and helium. The partial pressures of the three gases are 2.00 atm, 3.00 atm, and 4.00 atm, respectively. What is the total pressure inside the container? P total = P 1 + P 2 + P 3 + … P total = P O2 + + P CO2 + P He P total = 2.00 atm + 3.00 atm + 4.00 atm P total = 9.00 atm

9 Gas Collected Over Water: you need to account for the additional vapor pressure : P total = P gas + P H 2 O Note: most of the time, the total pressure is equal to the pressure inside the room!

10 Ex 2: Helium gas is collected over water at 25 °C. What is the partial pressure of the helium, given that the barometric pressure is 750.0 mm Hg? P total = P He + P H 2 O 750.0 mm Hg = P He + 23.8 mm Hg P He = 726.2 mm Hg

11 Ex 3: A student has stored 100.0 mL of neon gas over water on a day when the temperature is 28.0°C. If the barometer in the room reads 743.3 mm Hg, what is the pressure of the neon in its container? P total = P Ne + P H 2 O 743.3 mmHg = P Ne + 28.3 mm Hg P Ne = 715.0 mm Hg

12 Ex 4: A container has two gases, helium and argon. Suppose that the mixture contains 30% helium by volume. Calculate the partial pressure of helium AND argon if the total pressure of the container is 4.00 atm. Total pressure = 4.00 atm. 30% of 4.00 is 1.2 atm (0.30 X 4.00 atm = 1.2 atm) 70 % of 4.00 is 2.8 atm (0.70 X 4.00 atm = 2.8 atm) P He = 1.2 atm AND P Ar = 2.8 atm Double Check: P total = P He + + P Ar P total = 1.2 atm + 2.8 atm = 4.00 atm

13 Ex 5: A certain mass of oxygen was collected over water when potassium chlorate was decomposed by heating. The volume of the oxygen sample collected was 720 mL at 25°C and an atmospheric pressure of 750 mmHg. What would the volume of the oxygen be at STP? P 1 V 1 = P 2 V 2 T 1 T 2 P 1 (720ml) = (760mmHg)V 2 (273 + 25 ⁰ C) (273K) P total = P O2 + P H 2 O 750 mmHg = P O2 + 23.8 mmHg P O2 = 726.2 mmHg Answer: 630 mL (726.2 mmHg)(720ml) = (760mmHg)V 2 (298K) (273K)

14 Mystery Game: The Gas Problem Strikes BACK Directions: You will be given three TIMED gas law problems. (Exactly 3 minutes to do each problem…so work together). Your job is to find an answer to each mystery problem. The sum of all three mystery problems, ignoring sig fig rules, is: 757.15

15 The volume of a gas at 27.0°C and 0.200 atm is 80.0 mL. What volume will the same gas sample occupy at standard temperature and standard pressure? What pressure(atm) is required to reduce 60.0 mL of a gas at STP to 10.0 mL at a temperature of 25.0°C? A 250. mL sample of oxygen gas is collected over water at 25.0 °C and 760 mmHg. What is the pressure of the oxygen gas by itself?

16 add your answers to all 3 mystery problems and round to 3 sig figs! Mystery Problem #1 Mystery Problem #2 Mystery Problem #3 ANSWER (no units) ++= 14.6 mL + 6.55 atm + 736 mm Hg = 757.15


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