CHAPTER 5 GASES - PROBLEMS

  1. A sample tube containing 103.6 mL of CO gas at 20.6 torr is connected to an evacuated 1.13 liter flask (the new volume is the sum of those of the tube and flask). What will be the pressure when the CO is allowed into the flask?
  1. A gas has a pressure of 3.2 atm and occupies a volume of 45 L. What will the pressure be if the volume is compressed to 27 L at a constant temperature?
  1. A 11.2 L sample of a gas is determined to contain 0.50 moles of N2. At the same temperature and pressure how many moles of gas would there be in a 20. L sample?
  1. Consider a 3.57 L sample of an unknown gas at a pressure of 4300 Pa. If the pressure is changed to 21000 Pa at a constant temperature, what will the new volume of the gas be?
  1. A sample of gas occupies 3.8 L at 15C and 1 atm. What does the temperature need to be for the gas to occupy 8.3 L at 1 atm?
  1. Water is decomposed to H2(g) and O2(g) by electrolysis. By measuring the current it was determined that 0.365 moles of water were decomposed. After the gases are dried and collected at 24.5C and 757 torr what are the volumes of each?
  1. What pressure would be exerted by 50. g of He at 25C in a volume of 350 L?
  1. A vacuum line used in a research lab has a volume of 1.013 L. The temperature in the lab is 23.7C and the vacuum line is evacuated to a pressure of 1 x 10-6 torr. How many gas molecules (atoms) remain?
  1. Calculate the volume occupied by 2.5 mol of an ideal gas at STP.
  1. An unknown gas has a density of 7.06 g/L at a pressure of 1.5 atm and

280 K. Calculate the molar mass of the gas.

  1. HCl(g) can be prepared by reaction of NaCl with H2SO4. What mass of NaCl is required to prepare enough HCl to fill a 340. mL cylinder to a pressure of 151 atm at 20C?
  1. You are not sure whether to fill a balloon with He or hot air. To what temperature would the air have to be heated for a balloon to rise to the same height as a balloon filled with He at 25C?
  1. A 27.7 mL sample of CO2 (g) was collected over water at 25C and 1 atm. What is the pressure due to CO2 (g) (the vapor pressure of water at 25C is 23.8 torr)? What will the volume of CO2 (g) be at the same temperature and pressure after removing the water vapor?
  1. A gaseous mixture of O2, H2, and N2 has a total pressure of 1.5 atm and contains 8.2 g of each gas. Find the partial pressure of each gas in the mixture.
  1. The mole fraction of argon in dry air is 0.00934. How many liters of air at STP will contain enough argon to fill a 35.4 L cylinder to a pressure of

150 atm at 20C?

  1. The lower limit of flammability for H2 (g) in air at room temperature and 1 atm is a partial pressure of 0.040 atm. Assuming a 4:1 ratio of N2 to O2 in air, what is the ratio of H2 to O2 at its flammability limit?
  1. Calculate the rate of effusion of PH3 molecules through a small opening if NH3 molecules pass through the same opening at a rate of 8.02 cm3/s. Assume the same temperature and equal partial pressures of the two gases.
  1. Which gas would effuse faster Ne or CO2? How much faster?
  1. Calculate the pressure exerted by 100. moles of Cl2 gas in a 20. L container at 25C using the van der Waals equation and the constants from your book.
  1. Calculate the density of a mixture of 21% O2 and 79% N2 as well as for He at 760 torr and 0C. Will the ratio of densities be different at 100 atm and 6C?