The ratio Cp:Cv for an ideal gas = 1.4 and the specific heat measured at constant pressure is 1100 kJ/kgK. The gas flows through an adiabatic throttling valve and the pressure drops from 700 kPa to 150 kPa. The temperature before the valve is 100 C. What is the temperature after the valve?

a. –193 C

b. –33 C

c. 64 C

d. 100 C 

Which thermodynamic property is the best measure of the molecular activity of a substance?

A. Enthalpy

B. Internal energy

C. Entropy

D. External energy

Steam at 2.0 kPa has Tsat = 17.5 C. At 40 C, the steam will be:

A. superheated

B. subcooled

C. saturated

D. supersaturated

Which property of state is not an extensive property?

a. Temperature

b. Volume

c. Number of molecules

d. Mass

The dew point (°C) of moist air at 30°C and 30% relative humidity is most nearly: