One kg of air initially at 7 bar pressure and 360 k temperature expands poly tropically (pvL2 = const.) until the pressure reduced to 1.4 bar. Determine: (i) Final specific volume and temperature (ii) Change of internal energy (iii)  Work done and heat interaction. (iv) Change in entropy.

1.3 1 kg of air has a volume of 85 litres and a temperature of 150ºC. The air is heated at constant volume until the temperature is 250ºC. It is then expanded according to the law Pv1.3 = C until the pressure has halved. R for air is 0.287 kJ/kg.K and Cp = 1.005 kJ/kg.K.(a) Calculate the change in entropy during the constant volume heating process(b) Calculate the pressure at the beginning and end of constant volume process, the temperature and pressure at the end of expansion and the volume at the end of expansion.(c) Calculate the change in entropy during the expansion

1.56 moles of an ideal gas is placed in a piston and is subjected to the following changes. (a) The piston is locked so that the volume of the gas does not change, and is then cooled slowly (and reversibly!) from a temperature of 400 K to 300 K. What is the change in entropy, AS (in J/K), for this process? This is an example of an isochoric cooling process. (b) The external pressure around the piston is adjusted to match the internal pressure of the gas inside. The piston is now insulated from the surroundings (i.e. no heat exchange) and is unlocked. The external pressure is slowly (and reversibly!) increased allowing adiabatic contraction of the gas inside until its temperature has returned to 400 K. What is the change in entropy (in J/K) for this process? (c) What is the total change in entropy (in J/K) for these two processes, and in what way(s) are the physical properties of the gas (P, V, and 7) different between the starting point and the end point? (You may find it useful to…

For H20, determine the specific volume at the indicated state, in m3/kg. (a) T = 480°C, p = 20 MPa. (b) T= 80°C, p = 20 MPa. (c) T = 40°C, p = 2 MPa.