Please answer a,b and c. Please show all work. Thank you. 1) A substance undergo

Question

Please answer a,b and c. Please show all work.

Thank you.

1) A substance undergoes a cyclic but overall irreversible process between two heat reser- voirs at temperatures 400 C and 200 C. During the cycle, the substance does 200 and rejects 600 J of heat to the colder reservoir a) What is the heat flow from the hot reservoir in this cycle? b) What is the efficiency in this cycle? J of work Given that those "legs" (of this cyclic process) in which heat is exchanged with the two temperature reservoirs are isothermal and reversible. What is the change in entropy for c) the substance during the isothermal part of the cycle when in contact with just the cold reservoir?

Explanation / Answer

Temperature of cold reservoir Tc = 200C = 473K, temperature of hot reservoir Th = 400C = 673K, work done W = 200J and heat rejected Qc = 600J.

a) Work done = Heat absorbed - Heat rejected => W = Qh - Qc

=> Qh = W + Qc = 200 + 600 = 800J.

b) Efficiency = 1 - Qc/Qh = 1 - 600/800 = 25%.

c) The change in entropy S = Qc / Tc = -600 / 473 = -1.27 J/K.

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