A
12.6-g ice cube at
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Solution: Click For PDF Version In the process of reaching thermal equilibrium the 12.6 g of ice at
will first get heated to
 ,
then will melt by acquiring heat of fusion, and next will get heated
to
 ,
the temperature of the lake. We can assume the lake to be an
infinite heat reservoir at
.
The total heat for the sequence of changes in the ice cube at
to its becoming water at
will be supplied by the lake, which, as already mentioned, functions
like a heat reservoir at a constant temperature.We will use the following data in calculating the total change of entropy of the system.
Heat capacity
of water,
heat capacity
of ice,
heat of
fusion,
(i) The
change in entropy of the ice when the ice cube gets heated from
(ii) The
change in entropy of the ice in melting of 12.6 g of ice at
(iii) The
change in entropy of the 12.6g of water when it gets heated from
(iv) The total amount of heat supplied by the lake in the processes (i), (ii) and (iii) is
Therefore, the total change of entropy of the system will be
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The
change of entropy of the lake will be
