A gasoline engine absorbs 2500 J of heat at 250°C and expels 2000 J at a temperature of 50°C. What is the magnitude of the change in entropy (in J/K) for the system?
A)6.2
B)4.7
C)1.4
D)10.9
E)3.2

Question

Quizplus · Accepted Answer

The change in entropy (ΔS) is calculated using the formula ΔS = Q/T, where Q is the heat absorbed or expelled and T is the temperature in Kelvin. For the heat absorbed: ΔS1 = 2500 J / (250 + 273) K = 2500 / 523 = 4.78 J/K. For the heat expelled: ΔS2 = -2000 J / (50 + 273) K = -2000 / 323 = -6.19 J/K. The total change in entropy is ΔS = ΔS1 + ΔS2 = 4.78 - 6.19 = -1.41 J/K. The magnitude is 1.4 J/K.

A Gasoline Engine Absorbs 2500 J of Heat at 250°C