# college-chemistry-problem-set-on-gases-pressure

Problem Set 4 Note: You will need the table of vapor pressures of water on page 157 of your textbook

1. Oxygen can be produced in the laboratory by the thermal decomposition of potassium chlorate: KClO3 (s) â†’ KCl (s) + 3/2 O2 (g) Some potassium chlorate is decomposed and the oxygen produced is collected over water at 25Â°C and 780 torr total pressure. A total of 510 mL of gas is collected. a) Determine the mass of oxygen collected. b) Calculate the mass of KClO3 which was decomposed. c) The oxygen collected in this experiment is dried thoroughly to remove all traces of water vapor and stored in a 300. mL glass bulb at 55Â°C. Calculate the pressure inside the bulb.

2. A 1.00-liter vessel contains 5.00 grams of nitrogen (N2) and 1.50 grams of water at 25Â°C. a) Determine the RMS speed of nitrogen molecules and water molecules in the vapor phase at 25Â°C. b) Calculate the average kinetic energy per molecule of nitrogen and of water vapor at 25Â°C.

3. A syringe filled with air can be used to test the relationship between the temperature and the volume of a sample of gas. The syringe has a movable plunger that allows an enclosed sample of gas to be held at a constant external pressure, so the gas inside the syringe can be held at a constant total pressure of 1.00 atm while allowing the volume of the gas to increase or decrease. a) You fill a syringe with 5.0 mL of air at 25Â°C and 1.00 atm. How many moles of air are contained in the syringe? b) Assuming that the mole fraction of nitrogen in air is 0.79 and the mole fraction of oxygen in air is 0.21, determine the partial pressure of each gas, and the mass of each gas contained in the syringe. c) On repeating the experiment, you accidentally trap a small amount of water inside the syringe. (Assume that the water vapor reaches equilibrium inside the syringe, and neglect the volume of the liquid water which will be present.) Given a temperature of 25Â°C, a volume of 5.0 mL, and a total pressure of 1.00 atm, determine the partial pressure of water vapor and the partial pressure of air (without water vapor) inside the syringe. d) You increase the temperature of the syringe to 65Â°C; the total pressure remains 1.00 atm, but the volume increases. Determine the volume of the syringe at the new temperature. (Assume that the water vapor reaches equilibrium at 65Â°C.)

4. A mixture of CS2 (g) and excess O2 (g) is contained in a 20.0-liter reaction vessel at 130.0Â°C; the total pressure of the mixture is 3.00 atm. A spark causes the CS2 to ignite, and it burns completely according to the following equation: CS2 (g) + 3 O2 (g) Ã  CO2 (g) + 2 SO2 (g) The vessel and contents are returned to 130Â°C and the mixture of product gases (CO2, SO2, and unreacted O2) has a total pressure of 2.40 atm. Determine the partial pressure of each of these gases in the final product mixture.