Astone with heat capacity c = 1.2 j/k is left outside on a cold day to reach a temperature of 273.15 k. the stone is then brought inside where the air temperature is 293.15 k. the stone is used as the cold side of a reversible engine. (the air is the hot side.) what is the maximum work that can be accomplished ?

To solve the problem it is necessary to apply the concepts related to Helmholtz free energy. By definition in a thermodynamic system the Helmholtz energy is defined as

Where,

is the internal energy equivalent to

And means the change in entropy represented as

Note: C means heat capacity.

Replacing in the general equation we have to

The work done of a thermodynamic system is related by Helmholtz free energy as,

Replacing with our values we have,

Therefore the maximum work that can be accomplished is 0.858J