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CH 720 Name:
EXAM
Fall 1999
1) A simplified version of the van der Waals equation takes into account only the
excluded volumes of the molecules and has the form:
P(V-nb) = nRT
Use this equation of state to derive an expression to calculate reversible
isothermal work. (15 points)
2) An ideal gas is reversibly and adiabatically compressed. The initial volume of the
system is three times the final volume of the system. The initial temperature of
the system was 83 C and C p,m
is 3.5R. Calculate q, w, U m
, H
m
. (20 points)
3) A sample of liquid acetone (CH 3
2
CO weighing 0.700 g was burned in a bomb
calorimeter for which the heat capacity (including the sample) is 6937 J K
observed temperature rise was from 23.45 C to 25.15 C. Calculate U
m
and H
m
(20 points)
4) The “skin” of a futuristic spy plane is made of a material that has an expansion
coefficient of 2.33 x 10
K
- . When the plane is on the tarmac at 31.
0
C it leaks
fuel through 0.10 in gaps between the 1.0 ft x 1.0 ft x 0.50 in square plates of the
skin. To what temperature must the skin be raised to seal the leaks?(15 points)
7) One mole of a gas that obeys the equation of state in question 1) is compressed
isothermally from 12.5 L to 8.50 L at a temperature of 32.
0
C. Given that
and that b = 0.0552 L/mol calculate w, q, and U. (10 points)
V
U
T
