A 30-kg iron block and a 40-kg copper block, both initially at 808C, are dropped into a large lake at 158C. Thermal equilibrium is established after a while as a result of heat transfer between the blocks and the lake water. Determine the total entropy change for this process.

Explanation:

The given data is as follows.

    = 30 kg,       = 40 kg

    =

    =

Now, we will calculate the heat energy as follows.

                   =

                   = 877.5 kJ

and,    

                     =

                     = 1003.6 kJ

               =

               = 6.531 kJ/K

              =

              = -2.747 kJ/K

              =

              = -3.142 kJ/K

Now, we will calculate the total entropy as follows.

                = 6.531 kJ/K - 2.747 kJ/K - 3.142 kJ/K

                = 0.64 kJ/K

thus, we can conclude that the total entropy change for this process is 0.64 kJ/K.