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Thermodynamics and Ideal Gas

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First Law-Exercise:
Problem 1: A volume 10 m3 contains 8 kg of oxygen at a temperature of 300 K. Find the work necessary to decrease the volume to 5 m3, (a) at a constant pressure and (b) at constant temperature. (c) What is the temperature at the end of the process in (a)? (d) What is the pressure at the end of process in (b)? (e) Show both processes in the p-V plane. Problem 2: The temperature of an ideal gas at an initial pressure p1 and volume V1 is increased at constant volume until the pressure is doubled. The gas is then expanded isothermally until the pressure drops to its original value, where it is compressed at constant pressure until the volume returns to its initial value. (a) Sketch these processes in the p-V plane and in …show more content…

Neglecting friction between the piston and the cylinder wall, determine the heat transfer to the air, in kJ.

First Law- Additional Exercises:
Problem 13: A system executes a quasi-static process from an initial state 1 to a final state 2, absorbing 80 kJ of heat and expanding from 2.0 m3 to 2.25 m3 against a constant pressure of 1.5 bar. The system is brought back to its initial state by a non-quasi-static process, during which it rejects 100 kJ of heat. What is the work done during the second process? Problem 14: Three kg of air in a rigid container changes its state from 5.0 bar and 75oC to 12 bar while it is stirred. The heat absorbed is 195 kJ. Assume air to be an ideal gas with cv = 0.714 kJ/kg K. Determine the final temperature, change in thermal energy and work done. Problem 15: Two kg of air at 2.5 bar and 30oC forms a closed system. It undergoes a constant pressure process with heat addition of 450 kJ. Compute final temperature, change in enthalpy, change in thermal energy, and work done. Assume air to be an ideal gas, with a mol.wt of 29 kg/kmol and cv = 0.714 kJ/kg K. Problem 16: A perfectly insulated system contains 0.1 m3 of hydrogen at 30oC, 5.0 bar. It is stirred at constant pressure till the temperature reaches 60oC. Determine heat transferred, change in thermal energy, stirrer work, and net work. Treat hydrogen as an ideal gas with mol.wt. = 2 kg/kmol, γ = 1.4.

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