29. Ten cubic feet of air are cooled at a constant pressure of \( 80 \mathrm{psia} \). The initial temperature was \( 180{ }^{\circ} \mathrm{F} \) and the final temperature after cooling is \( 100^{\circ} \mathrm{F} \). Calculate the external work done in foot pounds.
A. \( -14,425.8 \mathrm{ft}-\mathrm{lb} \)
C. \( +12,455.8 \mathrm{ft}-1 \mathrm{~b} \)
B. \( +14,425.8 \mathrm{ft}-\mathrm{lb} \)
D. \( -12,455.8 \mathrm{ft}-\mathrm{lb} \)
30. Calculate the mass rate of flow of air through a pipeline with an inside diameter of 3.5 in. if the average velocity of air at \( 80^{\circ} \mathrm{F} \) and 20 psia is \( 110 \mathrm{ft} / \mathrm{min} \).
A. \( 0.833 \mathrm{lbm} / \mathrm{min} \).
C. \( 0.893 \mathrm{lbm} / \mathrm{min} \).
B. \( 0.733 \mathrm{lbm} / \mathrm{min} \).
D. \( 0.612 \mathrm{lbm} / \mathrm{min} \).
31. A cylinder piston arrangement as shown in the figure is made of a non-heat conducting material. The cylinder has a volume of \( 3 \mathrm{ft}^{\wedge} 3 \) and is connected to a steam source at \( 100 \mathrm{psia} \) and \( 500{ }^{\circ} \mathrm{F} \). The piston is held in position by air at 20 psia and a cooling coil is placed in the cylinder to maintain a constant air temperature of \( 100^{\circ} \mathrm{F} \). Determine the work done if the valve is opened until the pressure in the cylinder falls to 100 psia.
A. 17.8 BTU
C. 20.9 BTU
B. \( 18.8 \mathrm{BTU} \)
D. 19.2 BTU
32. Determine the mass of air when the pressure is \( 20 \mathrm{psi} \), and the temperature is \( 80^{\circ} \mathrm{F} \) in a closed chamber with dimensions of \( 30 \mathrm{ft} \times 20 \mathrm{ft} \) \( x 15 \mathrm{ft} \). Assume air to be an ideal gas.
A. \( 1,000 \mathrm{lb} \)
C. \( 900 \mathrm{lb} \)
B. \( 700 \mathrm{lb} \)
D. \( 800 \mathrm{lb} \)
\( 33.0 .3 \mathrm{~kg} \) of nitrogen gas at \( 100 \mathrm{kPa} \) and \( 40^{\circ} \mathrm{C} \) is contained in a cylinder. The piston is moved compressing nitrogen until the pressure becomes \( 1 \mathrm{MPa} \) and temperature becomes \( 160^{\circ} \mathrm{C} \). The work done during the process is \( 30 \mathrm{~kJ} \). Calculate the heat transferred from the nitrogen to the surroundings. Cv for Nitrogen is \( 0.75 \mathrm{~kJ} / \mathrm{kg} \) - K.
A. \( +3 \mathrm{~kJ} \)
C. \( +5 \mathrm{~kJ} \)
B. \( -3 \mathrm{~kJ} \)
D. \( \pm 5 \mathrm{~kJ} \)
34. A tank containing air is stirred by a paddle wheel. The work input to the paddle wheel is \( 9,000 \mathrm{~kJ} \) and the heat transferred to the surroundings from the tank is \( 3,000 \mathrm{~kJ} \). Determine the work done.
A. \( 0 \mathrm{~kJ} \)
C. \( 6,000 \mathrm{~kJ} \)
B. \( 12,000 \mathrm{~kJ} \)
D. \( 1,000 \mathrm{~kJ} \)
35. Air at 1.02 bar, \( 22^{\circ} \mathrm{C} \), initially occupying a cylinder volume of \( 0.015 \mathrm{~m}^{\wedge} 3 \), is compressed reversibly and adiabatically by a piston to a pressure of 6.8 bar. Calculate Final temperature and volume.
A. \( 234.24^{\circ} \mathrm{C}, 0.00837 \mathrm{~m}^{\wedge} 3 \)
B. \( 234.24^{\circ} \mathrm{C}, 0.00387 \mathrm{~m}^{\wedge} 3 \)
C. \( 441.61^{\circ} \mathrm{C}, 0.00837 \mathrm{~m}^{\wedge} 3 \)
D. \( 441.61^{\circ} \mathrm{C}, 0.00387 \mathrm{~m}^{\wedge} 3 \)
36. A steel flask of \( 0.04 \mathrm{~m}^{\wedge} 3 \) capacity is to be used to store nitrogen at \( 120 \mathrm{bar}, 20^{\circ} \mathrm{C} \). The flask is to be protected against excessive pressure by a fusible plug which will melt and allow the gas to escape if the temperature rises too high. How many \( \mathrm{kg} \) of nitrogen will the flask hold at the designed conditions?
A. \( 4.51 \mathrm{~kg} \)
C. \( 6 \mathrm{~kg} \)
B. \( 5.51 \mathrm{~kg} \)
D. \( 6.65 \mathrm{~kg} \)
37. A vessel of capacity \( 3 \mathrm{~m}^{\wedge} 3 \) contains \( 1 \mathrm{~kg} \) mole of \( N_{2} \) at \( 90^{\circ} \mathrm{C} \), calculate \( \mathrm{Cp} \) and \( \mathrm{Cv} \) if \( \mathrm{k}=1.4 \)
A. \( \mathrm{Cp}=1.039 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K}, \mathrm{Cv}=0.742 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K} \)
B. \( \mathrm{Cp}=1.390 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K}, \mathrm{Cv}=0.742 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K} \)
C. \( \mathrm{Cp}=1.039 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K}, \mathrm{Cv}=0.724 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K} \)
D. \( \mathrm{Cp}=1.390 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K}, \mathrm{Cv}=0.724 \mathrm{~kJ} / \mathrm{kg}-\mathrm{K} \)
38. A vessel of \( 0.03 \mathrm{~m}^{\wedge} 3 \) capacity contains gas at 3.5 bar pressure and \( 35^{\circ} \mathrm{C} \) temperature. If the pressure of this gas is increased to 10.5 bar while the volume remains constant what will be the temperature of the gas?
A. \( 924^{\circ} \mathrm{C} \)
C. \( 464^{\circ} \mathrm{C} \)
B. \( 651^{\circ} \mathrm{C} \)
D. \( 720^{\circ} \mathrm{C} \)
39. A vessel contains at 1 bar and \( 20^{\circ} \mathrm{C} \) a mixture of 1 mole of \( \mathrm{CO}_{2} \) and 4 moles of air. Calculate the mixture total mass. The volumetric analysis of air can be taken as \( 21 \% \) Oxygen and \( 79 \% \) Nitrogen
A. \( 170 \mathrm{~kg} \)
C. \( 159.36 \mathrm{~kg} \)
B. \( 163.73 \mathrm{~kg} \)
D. \( 150 \mathrm{~kg} \)
