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Reversible & Irreversible Processes Contributions by: John L. Falconer Department of Chemical and Biological Engineering University of Colorado Boulder,

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Presentation on theme: "Reversible & Irreversible Processes Contributions by: John L. Falconer Department of Chemical and Biological Engineering University of Colorado Boulder,"— Presentation transcript:

1 Reversible & Irreversible Processes Contributions by: John L. Falconer Department of Chemical and Biological Engineering University of Colorado Boulder, CO Supported by the National Science Foundation

2 When the red stops are removed, the ideal gases expand, and the pistons move until they hit the black stoppers. Each system is adiabatic. Which system has the most lost work? A.A B.B C.C D.Same for all systems 2 2 kg Vacuum Gas A 1 kg Vacuum Gas B Vacuum Gas C

3 In these piston-cylinder systems, when the red stop is removed, the ideal gas expands, and the piston moves until it hits the black stopper. Each system is adiabatic and starts at 10 atm and 25°C. Which has the highest final temperature? A.A B.B C.C D.All the same 3 2 kg Vacuum Gas Piston Block A 1 kg Vacuum Gas B Vacuum Gas C

4 A pile of sand sits on a piston and the weight of the sand keeps the gas compressed in the cylinder. Which method to remove the sand expands the gas most reversibly? A.All at once. B.One grain at a time. C.¼ th of the sand per minute. D.Same for all methods Gas Piston Sand

5 An ideal gas expands from 2 bar to 1 bar adiabatically but irreversibly. Compared to an adiabatic, reversible process from 2 bar to 1 bar, the final temperature will be _____________ for the irreversible process. A.higher B.lower C.the same

6 The curve represents an adiabatic reversible process for an ideal gas. For any starting point on the line, which regions cannot be reached by an adiabatic irreversible process? ABOVE U V U V BELOW U V ABC All regions can be reached

7 Which of these processes could run under continuous, steady-state operation? A.1 B.2 & 3 C.3 D.4 E.1 & 4 W Q W Q W Q W Q #1#2 #3#4

8 Which of the following processes could run under continuous, steady-state operation? A.1 B.2 & 3 C.3 D.4 E.1 & 4 W Q W Q W Q #2 #3 #4 #1 W QHQH hot cold QCQC

9 Which of the following processes could run under continuous, steady-state operation? A.1 & 2 B.3 & 4 C.3 D.4 E.1 & 3 W QHQH hot cold QCQC #1 W QHQH hot cold QCQC W QHQH hot cold QCQC W QHQH hot cold QCQC #2 #3 #4

10 Which of the following processes could run under continuous, steady-state operation? A.1 B.3 C.1 & 3 D.4 E.1 & 2 W QHQH hot cold QCQC #1 W QHQH hot cold QCQC W QHQH hot cold QCQC W QHQH hot cold QCQC #2 #3 #4

11 A gas goes from state A to state B in a reversible adiabatic process. It then goes from B back to A by a different pathway that is irreversible and not adiabatic. The entropy change for the gas for the irreversible pathway is _____________ zero. A.greater than B.less than C.equal to V P A B Rev. Irrev.

12 A gas goes from state A to state B in a reversible adiabatic process. It then goes from B back to A by a different pathway that is irreversible and adiabatic so that the entropy change of the gas is zero. Is this possible? A.Yes B.No C.Cannot tell V P A B Rev. Irrev.

13 Two reversible pathways are shown. Which one has the larger value of Q? A B C.Both have the same Q

14 Two reversible pathways are shown. Which one has the larger value of Q? A B C.Both have the same Q P V

15 Adiabatic expansions and compressions are shown for an ideal gas. One curve is reversible and one is irreversible in each figure. Which ones are the irreversible curves? A.1 & 3 B.1 & 4 C.2 & 3 D.2 & P T start 3 4 P T

16 Each figure has three curves for a gas: (isothermal, reversible adiabatic, and irreversible adiabatic). Which curves are the irreversible adiabatic curves? A.1 & 4 B.1 & 6 C.3 & 4 D.2 & 4 E.3 & 6 start P V P V 4 5 6

17 The three curves represent isothermal, reversible adiabatic, and irreversible adiabatic processes for a gas. Which curve represents the irreversible adiabatic process? A.1 B.2 C.3 D.Cannot be determined start P V 2 1 3

18 The three curves represent isothermal, reversible adiabatic, and irreversible adiabatic processes for a gas. Which curve represents the irreversible adiabatic process? A.1 B.2 C.3 D.Cannot be determined start P V 1 3 2

19 An ideal gas goes from 10 atm and 50 ° C to 1 atm and 100 ° C by two pathways. Path A is reversible, it is a constant volume step followed by a constant pressure step. Path B is irreversible, and is a constant pressure step followed by a constant volume step. Which pathway has the larger entropy change for the gas? A.A B.B C.They are the same 10 atm 50°C 1 atm 100°C 10 atm 50°C 1 atm 100°C V P P V A B

20 An inventor claims he can convert 1000 J of heat into 1000 J of work. Does this violate the second law? A.Yes B.Yes, if he claims to do it continuously C.No D.Cannot tell

21 Which process is the most irreversible? A.Slowly increasing pressure on the gas phase reaction 2A (g) 2B (g) B.Melting ice at 0°C by removing heat. C.Slowly blowing up a balloon. D.Slowly mixing 40°C water with 42°C water. E.Boiling water in a piston/cylinder at 1 atm, 100°C.

22 Which process is closest to being reversible? A. Slowly dissolving NaCl in water B. Slowly burning carbon in O 2 at 300°C C. Slowly compressing a gas in a piston-cylinder so that the gas heats up D. Expanding a gas through a nozzle to lower pressure

23 An ideal gas is compressed adiabatically and irreversibly. The final temperature of this process relative to that for an adiabatic reversible process to the same final pressure is ____________. A.higher B.lower C.the same

24 The work for irreversible compression of an ideal gas in a piston-cylinder system is _______ the work for reversible compression. A.higher than B.lower than C.the same as


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