A
mass m of water at
and prove that this is positive. |
Solution: Click For PDF Version As equal amounts of water equal to m at temperatures
and
 are
mixed. It is given that the process is carried out isobarically and
adiabatically. It means that the exchange takes place between the
two equal mass water samples only and there is no exchange of heat
with the surroundings.
Therefore,
when thermal equilibrium is reached the temperature of water will
become
We
will calculate the change in entropy by using reversible
thermodynamic processes in which the samples of
water at temperatures
We have
Or
Note that
Therefore,
|
The thermodynamic process is irreversible.
gradually and the entropy change can be calculated using the result
We
will next show that
,
as is required by the second law of thermodynamics for an
irreversible process.