Below are five properties, with an example of the units in which that property could be expressed. Which units are wrong for the property?
A. Specific volume, in m3/kg
B. Molar enthalpy, in kJ/mol
C. Specific internal energy, in kJ/mol
D. Enthalpy, in N•m
E. The parameter “a” in the van der Waals equation, in Pa•m6/mol2
A. Incorrect. Specific volume, or inverse density, is expressed as volume per mass.
B. Incorrect. Enthalpy is expressed as energy. Molar enthalpy is therefore energy per amount of substance (moles)
C. Correct. “Specific” quantities are expressed as being per unit mass, such as specific internal energy (kJ/kg). The units given would be valid for molar internal energy.
D. Incorrect. While expressed in unusual units, newton-meters are valid units for enthalpy.
E. Incorrect. The “a” in van der Waals is expressed in those units. See Example 2-6.
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