Chapter 6, Problem 6.92P

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…

0.5 mol of an ideal gas (with Cv,m=5/2R or 2.5R) that is initially held at V=2.5L and P=1.2atm expands to P=0.75atm. Solve for the new volume assuming that the process was adiabatic and reversible.

EXERCISES ON PROPERTIES OF STEAM 1. A vessel of volume 0.04 m3 contains a mixture of saturated water and steam at a temperature of 250°C. The mass of the liquid present is 9 kg. Find the pressure, mass, specific volume, enthalpy, entropy and internal energy.