NORTH CAROLINA STATE UNIVERSITY

Department of Chemistry Name________________________________

 

CH 431  Take-home Quiz 1

Physical Chemistry I  Sept. 7 2001

                                                                                         Due Date: Sept. 13 2001

 

Show some work/reasoning for each answer.   No explanation = no credit. 

You are encouraged to work in pairs or groups.

In the problems below you may assume that the molar mass of the atmosphere is M = 29 a.u. on average.  Assume that all gases can be treated as ideal gases.

 

1.      A.  Given that the area of a sphere is 4pR2, where R is the radius, calculate the total mass of the earth’s atmosphere.  You may take R to be 6.37 x 106 m. (4 points)

 

 

 

 

 

 

 

 

 

  1. The volume fraction of carbon monoxide present in the atmosphere is 0.1 ppm (parts per

million).  When the components of the atmosphere are expressed as volume fraction they are also equal to the mole fraction (why?).  Calculate the partial pressure of CO and the total mass of CO in the atmosphere. (3 points)

 

 

 

 

 

 

 

 

C.  The volume fraction of CO2 in the atmosphere has increased from 290 ppm in 1900 to 350 ppm at present.  Assuming that all of the increase comes from combustion of fossil fuels, how many metric tons of CO2 does this increase represent? (3 points)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

2.    The barometric formula

 

                                                                  p = p0exp(-Mgh/RT)

 

      relates the pressure of a gas of molar mass M at an altitude h to its pressure p0 at sea level.  This relation can be derived starting with the change in pressure dp for an infinitesimal change in altitude dh given as:

 

                                                                         dp = -rg dh.

 

      Recently climbers have been able to climb to the peak of Mt. Everest without oxygen tanks. Calculate the pressure at an elevation of 8000 meters at 260 K (2 points)

 

 

 

 

 

 

 

 

  1. Calculate the pressure exerted by 1 mol of ethene behaving as (a) an ideal gas, (b) a van der Waals gas [see Table 16.3 use the constants from the second and third columns in the table], when it is confined under the following conditions:
    (i) at 273 K in 22.414 L. (4 points)

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(ii) at 1000 K in 100 cm3. (4 points)