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Question
Calculate the entropy change in the system, and surroundings, and the total entropy change in the universe during a process in which 245 J of heat flows out of the system at 77°C to the surrounding at 33°C.
Solution
Given, Tsys = 77°C = (77 + 273) = 350 K
Tsurr = 33°C = (33 + 273) = 360 K
q = 245 J
∆Ssys = `"q"/"T"_"sys" = (−245)/350` = − 0.7 JK−1
∆Ssurr = `"q"/"T"_"sys" = (+245)/306` = + 0.8 JK−1
∆Suniv = ∆Ssys + ∆Ssurr
∆Suniv = − 0.7 JK−1 + 0.8 JK−1
∆Suniv = 0.1 JK−1
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