Chemistry 343                                                           Assignment # 1

Fall 2005                                                                     Due Mon. 5 Sept at 9:00am

 

 

Problem

Responsible Student

Ch. 24:          1

Blohm

3

Buchan

4

Campbell

5

Cox

6

Davisson

7

Goetz

Special Prob 1

B-Lajiness

Special Prob 2

J-Lajiness

 

 

Special Problem 1:

The barometric formula relates the pressure of a gas of molar mass M at an altitude a to its pressure po at sea level. 

 

a) Derive the barometric formula given above by first deriving the following expression for the change in pressure resulting from an infinitesimal change in altitude:  dp = -r g da. 

 

Hints:  1)  Note that pressure is generally defined as force over area:

 

                       

 

 

2)  The column height (h) given in hint 1) is the amount of air that is above the location of interest.  The altitude (a) given in the barometric formula is the distance the location of interest is above sea level.

3)  To derive the barometric formula, remember that r depends on pressure.

 

 

b)  Quantitatively evaluate the pressure difference between the top and bottom of

1) one floor of the Sears tower, 12.9 ft.

2) the entire Sears tower, 1450 ft.

 

 

Special Problem 2: 

0)  DonŐt worry about quantitative analysis in this problem, be more concerned with relative ordering and trends.

a)  Based on the electronegativity of the halogen atoms, arrange the hydrogen halides (HF, HCl, HBr, HI) in increasing dipole moment value order.  Ignore any effects from differing bond lengths.

b)  Rearrange the hydrogen halides, this time considering only bond-length effects and ignoring electronegativity. 

c)  Look up gaseous dipole moments for the hydrogen halides (in the CRC, for example) and rationalize the relative importance of electronegativity and bond length for this class of molecules.

d)  Next, arrange the hydrogen halides in increasing order of the total number of electrons each possesses. 

e)  Look up the boiling points of the hydrogen halides (in the CRC, for example) and rationalize the ordering of the boiling points in terms of the relative importance of electrostatic and dispersion forces for each of the hydrogen halides.