Gases

 

The following problems are taken from T. L. Brown, H. E. Lemay, B. E. Bursten, & J. R. Burdge, Chemistry: The Central Science, Ninth Edition, Chapter 10. To see the solution to a problem or to return from the solution, click on the number of the problem.

 

20) A sample of gas occupies a volume of 1248 ft3 at 0.988 atm and 28.0°C.

       (a) Calculate the pressure of the gas if its volume is decreased to 978 ft3 while its temperature is held constant.

       (b) At what temperature in degrees Celsius is the volume of the gas 1435 ft3 if the pressure is kept constant?

                    

26) Suppose you are given two flasks at the same temperature, one of volume 2 L and the other of volume 3 L. In the 2-L flask the gas pressure is X atm, and the mass of gas in the flask is 4.8 g. In the 3-L flask the gas pressure is 0.1X, and the mass of gas is 0.36 g. Do the two gases have the same molar mass? If not, which contains the gas of higher molar mass?

      

32) An aerosol spray can with a volume of 456 mL contains 3.18 g of propane gas (C3H8) as a propellant.

      (a) If the can is at 23°C, what is the pressure in the can?

      (b) What volume would the propane occupy at STP?

      (c) The can says that exposure to temperatures above 130°F may cause the can to burst. What is the pressure in the can at this temperature?

     
46) Calcium hydride, CaH2, reacts with water to form hydrogen gas: 

      CaH2(s) + 2H2O(l)  Ca(OH)2(aq) + 2H2(g)     

      This reaction is sometimes used to inflate life rafts, weather balloons, and the like, where a simple, compact means of generating H2 is desired. How many grams of CaH2 are needed to generate 64.5 L of H2 gas if the pressure of H2 is 814 torr at 32°C?

      

60) A sample of 5.25 g of SO2(g) originally in a 4.00-L vessel at 26°C is transferred to a 13.6-L vessel at 25°C. A sample of 2.35 g N2(g) originally in a 3.18-L vessel at 20°C is transferred to this same 13.6-L vessel.

      (a) What is the partial pressure of SO2(g) in the larger container?

      (b) What is the partial pressure of N2(g) in this vessel?

      (c) What is the total pressure in the vessel?

      

66) Suppose you have two 1-L flasks, one containing N2 at STP, the other containing CH4 at STP. How do these systems compare with respect to:

      (a) number of molecules

      (b) density

      (c) average kinetic energy of the molecules

      (d) rate of effusion through a pinhole leak?

         

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