Unit 2 Worksheet 3 – PVTn Problems Name Date Pd On each of the problems below: A. Draw particle diagrams of the initial and final conditions. B. Organize given information (P, V, T, n) with Initial/Final/Effect Table. C. Make a decision as to how a change in P, V, T, or n will affect the starting quantity (show with arrows up or down in Effect line – example: P↑ V↓ - which means if the pressure increases, the volume decreases) D. Setup conversion equation by multiplying by the appropriate factors. 1. You collect a sample of gas that occupies 150 mL at 25 ˚C. What is its volume when you increase the temperature to 50˚C? (P and n = constant) P T V n Initial Final Effect 2. What would be the new pressure if 250 cm3 of gas at standard pressure is compressed to a volume of 150 cm3 ? ( = constant) 3. What would be the new volume if 250 cm3 of gas at 25˚C and 730 mm pressure were changed to standard conditions of temperature and pressure? ( = constant) 4. Your bike tire contains 15 units of air particles, has a volume of 160mL, and has a pressure of13 psi. Your tire develops a leak. Now it contains 10 units of air and has contracted to a volume of 150mL. What is the tire pressure now? Modeling Chemistry 1 U2 ws 3 v2.1 5. A closed flask of air (0.250L) contains 5.0 units of particles. The pressure probe on the flask reads 93 kPa. You use a syringe to add an additional 3.0 units of air through the stopper. What is the new pressure inside the flask? 6. You have a 350 mL sample of gas with a temperature of 30˚C and a pressure of 1.20 atm. What temperature would needed for the same amount of gas to fit into a 250 mL flask at standard pressure? 7. A 475 cm3 sample of gas at standard temperature and pressure is allowed to expand until it occupies a volume of 600. cm3. What temperature would be needed to return the gas to standard pressure? Go to http://mc2.cchem.berkeley.edu/Java/molecules/index.html 8. You buy a bike and pump up the tires with the intention of getting some exercise. But as things go, you don’t touch it for six months. When you finally get to it, the tires are flatter than before. If you assume that the tires are completely sealed (no additional air in or out), explain why this has occurred. Modeling Chemistry 2 U2 ws 3 v2.1
