Densities of water at 4 and 20 are 1000 kg/m3 and 998 kg/m3 respectively. The increase in internal energy of 4 kg of water when it is heated from 4 to 20 is J. (specific heat capacity of water = 4.2 kJ/kg K and 1 atmospheric pressure = 105 Pa)
- 268799.2
- 315826.2
- 234699.2
- 258700.8
Answer
(1) 268799.2
Solution
Heat supplied: Q = mc T = 4 4200 16 = 268800 J
Volumes: V1 = 41000 = 4 10-3 m3, V2 = 4998 = 4.008016 10-3 m3
V = 8.016 10-6 m3
Work done by water at atmospheric pressure: W = P V = 105 8.016 10-6 = 0.8016 J
First law: U = Q - W = 268800 - 0.8016
U 268799.2 J
Answer: (1)