Which of the following statements is false?

Question

A. The constant volume heat capacity of an ideal gas is a function of temperature only.
B. The internal energy of an ideal gas is a function of both temperature and pressure.
C. There is no explicit “flow work” term in the generalized energy balance because flow work is accounted for in the enthalpy term.
D. The specific volume of a liquid is frequently modeled as constant with respect to temperature and pressure.
E. In some cases such as low pressures or low volumes, enthalpy and internal energy values are essentially identical.

Answer 1

A. Incorrect. This statement is true. Review Section 2.3.3.
B. Correct. Internal energy of an ideal gas is a function of temperature only.
C. Incorrect. This statement is true. Flow work is defined as PV and enthalpy is U + PV, therefore the enthalpy terms (H) include flow work.
D. Incorrect. This statement is true. Especially when the temperature changes are small, specific volume changes are so small they can be ignored. Figure 2-2 shows the almost invisible effect of pressure on liquid volume (practically vertical lines to the left of the envelope by the axis).
E. Incorrect. This statement is true. Since H = U + PV, if the PV term is small compared to U, H ? U. This does not mean they should be considered interchangeable in all cases though.