- Calculate the change in entropy when 10 kg of air is heated at constant volume from a pressure of 101325 N/m
^{2}and a temperature of 20^{o}C to a pressure of 405300 N/m^{2}. C_{V}= 20.934 kJ/kmol.^{o}C. - Calculate the total change in entropy for the following processes:
- One gram mole of an ideal gas (C
_{P}= 7 cal/gmol.^{o}K) is cooled at 10 atmosphere absolute pressure from 500 K to 300 K, and then expanded isothermally to 1 atmosphere absolute pressure and 300 K. - 100 grams of lead shot (C
_{P}= 0.03 cal/gm.^{o}C) originally at 300^{o}C is mixed with 100 grams of water at 30^{o}C. - One kg of air is heated reversibly from an initial state of 1 atm and 10
^{o}C to 1 atm and 65^{o}C. For reversible heating of air at constant pressure, dQ/dT = 0.24 kcal/kg.^{o}C. Determine the change in entropy. - A heat engine receives 500 BTU of heat per cycle from a reservoir at 540
^{o}F and rejects heat to a sink in a hypothetical amounts of (a) 375 BTU per cycle (b) 250 BTU per cycle and (c) 150 BTU per cycle. Which of these respective cases represent a reversible cycle, an irreversible cycle and an impossible cycle? - What is the change in entropy when one gram mole of an ideal gas at 21
^{o}C and a pressure of 10 kgf/cm^{2}expands through a throttle valve to a pressure of 1 kgf/cm^{2}. The value of the gas constant R = 1.987 cal/gmol.^{o}K - A lump of copper having a mass of 10 gm at a temperature of 500
^{o}C is just dropped into a well insulated bucket containing 100 gm of water at a temperature of 50^{o}C. If the heat capacities of copper and water are 0.095 and 1.0 respectively, expressed as cal/gm.^{o}C, calculate the total change in entropy resulting from the process. - One gram mole of a perfect gas with C
_{P}= 7 cal/gmol.^{o}K is to be expanded from 10 atm and 500 K to 1 atm and 300 K by two reversible paths. - Cool at 10 atm from 500 K to 300 K and expand isothermally to 1 atm at 300 K.
- Expand at 500 K to the final volume and cool at constant volume to 300 K.
- A heat exchanger uses 5000 kg/hr of water to cool a hydrocarbon oil from 140
^{o}C to 65^{o}C. The oil , flowing at the rate of 2500 kg/hr has an average specific heat of 0.6 kcal/kg.^{o}C. The water enters at 20^{o}C. Determine - The entropy change of the oil
- Entropy change of water
- The total entropy change as a result of this heat exchange process.
- 15 kg of air at 200
^{o}C and 10 kgf/cm^{2}is cooled to 0^{o}C and a volume of 1.2 m^{3}. Determine the change in entropy. - 2 kg of oxygen execute an internally reversible process whereby heat is received causing the total entropy to increase to 0.3833 kcal/
^{o}C. For an initial temperature of 94^{o}C, determine the final temperature, if the process is (a) constant volume (b) constant pressure. For oxygen, C_{P}= 0.1572 kcal/kg.^{o}C; C_{V}= 0.2193 kcal/kg.^{o}C. - A 50 kg hot steel ball at 100
^{o}C (C_{P}= 0.02 cal/gm.^{o}C) is cooled in atmospheric air at 25^{o}C. Find total entropy change. - 1 kg (Molecular weight = 16)of an ideal gas at 25
^{o}C, 1 atm is mixed with 2 kg (Molecular weight = 40) of another ideal gas at 100^{o}C and 30 atm. What is the total entropy change. Assume C_{P}= 20 kJ/kmol.^{o}K. - Calculate the enthalpy, entropy and molal heat capacity at constant volume (C
_{V}) of 1 gmol of nitrogen at 527^{o}C and 100 atmosphere absolute pressure, assuming it to be an ideal gas.

Data:

C_{P}in cal/gmol.^{o}C = 6.5 + 0.001 T, where the temperature T is in^{o}K.

Enthalpy is zero at 0^{o}C, and 1 atmosphere absolute pressure.

Enthalpy is 45.8 cal/gmol.^{o}K at 25^{o}C and 1 atmosphere absolute pressure.

What is the change in entropy for the gas over each path? Derive the equations used.

Last Modified on: 04-Feb-2022

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