Gas Laws – Chapter 10 Name______
Mr. Citta – Homework 2-22-06 Date______
Equations:
PV=nRT
P1V1 = P2V2
T1 T2
R = .0821 l-atm/mole-K
R = 8.31 l-kPa/mole-k or joule/mole-k
R = 62.4 l-mmHg/mole-k
(pick the appropriate R based on unit of pressure used. Make sure liters is converted to milliliters, if milliliters if given in an equation. Or the milliliters converts to liters.)
Problems:
1. The pressure exerted on a 240 ml sample of hydrogen gas at constant temperature is increased from .428 atm to .724 atm. What will the final volume of the sample be? (ans. = 142 ml)
2. A sample of air has a volume of 140 ml at 67OC. At what temperature will its volume be 50.0 ml at constant pressure? (ans. = 121 K)
3. At standard temperature, a gas has a volume of 275 ml. The temperature is then increased to 130OC, and the pressure is held constant. What is the new volume? (ans. = 406 ml)
4. A sample of hydrogen at 47OC exerts a pressure of .329 atm. The gas is heated to 77OC at constant volume. What will its new pressure be? (ans. = .360 atm)
5. To what temperature must a sample of nitrogen at 27OC and .625 atm be taken so that its pressure becomes 1.125 atm at constant volume? (ans. = 540 K)
6. A 350 ml air sample collected at 35OC has a pressure of 550 torr. What pressure will the air exert if it is allowed to expand to 425 ml at 57OC? (ans. = 485 Torr)
7. A sample of oxygen at 40OC occupies 820 ml. If this sample later occupies 1250 ml at 60OC and 1.40 atm, what was its original pressure? (ans. = 2.01 atm)
8. Calculate the volume in liters, occupied by 2.00 moles of hydrogen at 300K and 1.25 atm. (ans. = 39.4 l)
9. Find the mass of 5.60 liters of O2 at 1.75 atm and 250K. (hint, find moles first and convert moles to grams.) (ans. = 15 grams)
10. Calculate the volume in liters occupied by 4.00 grams of O2 at 57OC and .888 atm.(see above hint in reverse) (ans. = 3.81 l)
Extra credit: Find the molar mass of an unknown gas if you have the following information: 1.05 grams of a gas occupy 2.35 liter at 37OC and .840 atm. (hint, define molar mass and see what you know and what you need to know.)