One end of a metal rod is in contact with a reservoir at a 400 K and the other end in contact with a reservoir at 200 K.The rod and reservoirs make up a closed system.If 5500 J are conducted from one end to the other uniformly (no change in temperature along the rod)what is the change in entropy of the 200 K reservoir?

Question

Quizplus · Accepted Answer

We can use the formula ∆S = Q/T, where Q is the amount of heat transferred and T is the temperature of the reservoir. 
Since the heat is flowing from the hotter reservoir to the colder reservoir, the entropy change of the hot reservoir is negative and the entropy change of the cold reservoir is positive. 
The change in entropy of the colder reservoir can be calculated as ∆S = Q/T = 5500 J / 200 K = 27.5 J/K. 
Therefore, the best choice is (A) 27.5 J/K.

One End of a Metal Rod Is in Contact with a Reservoir