Chapter 13 | 71513–102 One compartment of an insulated rigid tank con-
tains 2 kmol of CO 2 at 20°C and 150 kPa while the other
compartment contains 5 kmol of H 2 gas at 35°C and 300 kPa.
Now the partition between the two gases is removed, and the
two gases form a homogeneous ideal-gas mixture. The tem-
perature of the mixture is
(a) 25°C (b) 29°C (c) 22°C (d) 32°C (e) 34°C
13–103 A piston–cylinder device contains an ideal-gas mix-
ture of 3 kmol of He gas and 7 kmol of Ar gas at 50°C and
400 kPa. Now the gas expands at constant pressure until its
volume doubles. The amount of heat transfer to the gas mix-
ture is
(a) 6.2 MJ (b) 4.2 MJ (c) 27 MJ
(d) 10 MJ (e) 67 MJ
13–104 An ideal-gas mixture of helium and argon gases
with identical mass fractions enters a turbine at 1200 K and
1 MPa at a rate of 0.3 kg/s, and expands isentropically to
100 kPa. The power output of the turbine is
(a) 478 kW (b) 619 kW (c) 926 KW
(d) 729 kW (e) 564 kWDesign and Essay Problem
13–105 Prolonged exposure to mercury even at relatively
low but toxic concentrations in the air is known to cause per-
manent mental disorders, insomnia, and pain and numbness
in the hands and the feet, among other things. Therefore, the
maximum allowable concentration of mercury vapor in the
air at work places is regulated by federal agencies. These reg-
ulations require that the average level of mercury concentra-
tion in the air does not exceed 0.1 mg/m^3.
Consider a mercury spill that occurs in an airtight storage
room at 20°C in San Francisco during an earthquake. Calcu-
late the highest level of mercury concentration in the air that
can occur in the storage room, in mg/m^3 , and determine if it
is within the safe level. The vapor pressure of mercury at
20°C is 0.173 Pa. Propose some guidelines to safeguard
against the formation of toxic concentrations of mercury
vapor in air in storage rooms and laboratories.cen84959_ch13.qxd 4/6/05 9:35 AM Page 715