Answer to Question #287321 in Physics for Josie

Question

1 (a) 1kg of water at a temperature of 20◦C is placed in contact with a cold reservoir held at a constant temperature of 4◦C. (i) What is the change in the internal energy of the water as it cools to 4◦C ? (The specific heat capacity of water is 4148 J K−1 kg−1 .) [1] (ii) Calculate the change in entropy of the water as it cools to 4◦C. [2] (iii)Calculate the change in entropy of the cold reservoir. [2] (iv) Is this process of cooling the water reversible or irreversible? Explain your answer. [1]

v) Assume now that rather than being placed in a direct contact with the cold reservoir the water is cooled from 20◦C to 4◦C by using the water as the heat source for a reversible heat engine. The cold reservoir still has a fixed temperature of 4◦C. How much work can be extracted from this heat engine? [6]

I need help with part (v) only, just including the above parts for context

Answer 1

Since no change in volume occurs, no mechanical work can be extracted from this heat engine.