The divided tank of the preceding problem is replaced with two interconnected tanks of equal volume; one tank is initially evacuated, and the other contains methane at 500 bar and 20°C. A valve connecting the two tanks is opened only long enough to allow the pressures in the tanks to equilibrate. If there is no heat transfer between the gas and the tanks, what are the temperature and pressure of the gas in each tank after the valve has been shut? Assume that methane 

a. Is an ideal gas 

b. Obeys the principle of corresponding states of Sec. 6.6 

c. Obeys the Peng-Robinson equation of state