Question

A 47000 kg iceberg at −9.1 ◦C breaks away from the polar ice shelf and floats away into the ocean at 6.85◦C. What is the final change in the entropy of the system, when the iceberg has completely melted? The specific heat of ice is 2010 J/kg · ◦C. Answer in units of J/K.

Answer 1

Explanation:

As it is known that relation between heat and specific heat is as follows.

                    Q = $mC \Delta T$      

Heat evolved during phase change for temperature $-9.1^{o}C$ to $0 ^{o}C$ is as follows.

                  Q = $mC \Delta T$      

                      = $47000 kg \times 2010 J/kg ^{o}C \times (0 - (-9.1))^{o}C$

                      = 859677000 J   ............ (1)

Heat evolved during phase change for temperature $0 ^{o}C$ to $0 ^{o}C$ is as follows.

                       Q = $mC \Delta T$      

As temperature remains constant so, heat released will be equal to Q = m × l. Where l is latent heat of fusion on water equals 334 J/g.

                     Q = m × l

                         = $47000 kg \times 334 J/g \frac{1000 g}{1 kg}$

                         = 15698000000 J   ........... (2)

Heat evolved during phase change for temperature $0 ^{o}C$ to $6.85 ^{o}C$ is as follows.

                       Q = $mC \Delta T$      

                           = $47000 kg \times 2010 J/kg ^{o}C \times (0 - 6.85)^{o}C$      

                          = 647119500 J   .......... (3)

Now, total heat will be the sum of equations (1) + (2) + (3) as follows.

                   859677000 J + 15698000000 J + 647119500 J

                 = 17204796500 J

Also, relation between entropy and heat is as follows.

                      $\Delta S = \frac{Q}{\Delta T}$

                                 = $\frac{17204796500 J}{288.95 K}$

                                 = 59542469.28 J/K

Thus, we can conclude that final change in entropy is 59542469.28 J/K.