Problem Set

1  The average barometric pressure at an altitude of 10 km is 210 mm Hg.  Express this pressure in atmospheres, bars, and kilopascals?


2  A sample of CO2 gas is placed in a 125-mL flask where it exerts a pressure of 67.5 Hg.  What is the pressure of this gas sample when it is transferred to a 500-mL flask at the same temperature?


3  You have 3.5 of helium at a temperature of 22.0 C?  What volume would the helium occupy  at 37 C?  The pressure of the helium sample is constant.


4 One of the cylinders of a automobile engine has a volume of 400. Cm3.  The engine takes in air at a pressure of 1.00 atm and a temperature of 15 C and compresses it to a volume of 50.0 cm3 at 77 C.  What is the final pressure of the gas in the cylinder?  (The ratio of before and after volumes, in this case 400:50, or 8:1, is called the compression ratio.)


5 If you have a 150.-L tank of gaseous nitrogen, and the gas exerts a pressure of 41.8 Hg at 25 C, how many moles of nitrogen are in the tank?


6.  A hydrocarbon, CxHy, is 82.66% Carbon.  Experiment shows that 0.218g of hydrocarbon has a pressure of 374mm Hg in a 185-ml flask at 23 C. What are the empirical and molecular formulas of the compound?


7.  Forty miles above the earth's surface the temperature is 250K and the pressure is only 0.20 mm Hg.  What is the density of air in grams per liter at this altitude?  (Assume the molar mass of the air is 29 g/mol.




8 Iron reacts with acid to produce iron (H) chloride and hydrogen gas.

      Fe (s) + 2 HCI (aq)----FeCl2 (aq)  +  H2 (g)

      The H2 gas from the reaction of 1.0g of iron with excess hydrochloric acid is collected in a 15.0-L flask at 25 C.  What is the pressure of the H2 gas in this flask?


9 A sample of nitrogen gas is collected over water at 18 C.  If the barometric pressure in the lab is 747 mm Hg, what is the partial pressure of the dry nitrogen gas in the sample?  


10  You are given two flasks of equal volume.  Flask A  contains H2 at 0 C and 1 atm pressure.  Flask B contains CO2 gas at 0 C and 2 atm pressure.  Compare these two gases with respect to each of the following:

A. Average kinetic energy per molecule.
B. Average molecular velocity.
C. Number of molecules.
D. Mass of gas



11  Argon gas is ten times as dense as helium gas at the same temperature and pressure.  Which gas effuses faster?  How much faster?