Question

A solid metallic cube of heat capacity s is at temperature 300k. It is brought in contact with a reservoir at 600k. If the heat transfer takes place only between the reservoir and the cube, the entropy change of universe after reaching the thermal equilibrium is

Answer 1

The entropy change of universe after reaching the thermal equilibrium is 0.19S.

Given-

• Heat capacity of solid metallic cube = S
• Temperature = 300 K
• Temperature of reservoir = 600 K

We know that heat taken by the cube is given by

Q = S (ΔT) where Q is heat taken, S is heat capacity and ΔT is change in temperature

By substituting the values we get

Q = S ( 600 - 300)

Q = 300S J

Entropy change of reservoir is = -δQ/T = -300S/600 = -0.5S

Entropy change of the cube will be = 5 ln 600/300 = 0.69S

So,

Change in entropy of universe after reaching the thermal equilibrium is

ΔS universe = -0.5S + 0.69S = 0.19S