Thermodynamics

13–102 One compartment of an insulated rigid tank contains2 kmol of CO 2 at 20°C and 150 kPa while the othercompartment contains 5 kmol of H 2 gas at 35°C and 300 kPa.Now the partition between the two gases is removed, and thetwo gases form a homogeneous ideal-gas mixture. The temperatureof the mixture is(a) 25°C (b) 29°C (c) 22°C (d ) 32°C (e) 34°C13–103 A piston–cylinder device contains an ideal-gas mixtureof 3 kmol of He gas and 7 kmol of Ar gas at 50°C and400 kPa. Now the gas expands at constant pressure until itsvolume doubles. The amount of heat transfer to the gas mixtureis(a) 6.2 MJ (b) 4.2 MJ (c) 27 MJ(d ) 10 MJ (e) 67 MJ13–104 An ideal-gas mixture of helium and argon gaseswith identical mass fractions enters a turbine at 1200 K and1 MPa at a rate of 0.3 kg/s, and expands isentropically to100 kPa. The power output of the turbine is(a) 478 kW (b) 619 kW (c) 926 KW(d ) 729 kW (e) 564 kWChapter 13 | 715Design and Essay Problem13–105 Prolonged exposure to mercury even at relativelylow but toxic concentrations in the air is known to cause permanentmental disorders, insomnia, and pain and numbnessin the hands and the feet, among other things. Therefore, themaximum allowable concentration of mercury vapor in theair at work places is regulated by federal agencies. These regulationsrequire that the average level of mercury concentrationin the air does not exceed 0.1 mg/m 3 .Consider a mercury spill that occurs in an airtight storageroom at 20°C in San Francisco during an earthquake. Calculatethe highest level of mercury concentration in the air thatcan occur in the storage room, in mg/m 3 , and determine if itis within the safe level. The vapor pressure of mercury at20°C is 0.173 Pa. Propose some guidelines to safeguardagainst the formation of toxic concentrations of mercuryvapor in air in storage rooms and laboratories.