If a source says “the internal energy of the methane is U = 100 J/mol,” which of the following is true?

Question

A. In order to lower the temperature of the methane to absolute zero, you would have to remove 100 joules of heat from each mole of methane.
B. In order to convert the methane from its current state to the reference state, 100 joules of heat would need to be added to each mole of methane.
C. In order to convert the methane from its current state to the reference state, 100 moles of energy would need to be added to each mole of methane, but the energy added could take the form of either work or heat.
D. 100 joules, divided by the number of molecules in one mole, equals the average kinetic energy of the methane molecules, but the kinetic energy of individual molecules vary widely.
E. None of the above are true.

Answer 1

A. Incorrect. This is not true. The value 100 J/mol is relative to a reference state, not relative to absolute zero.
B. Incorrect. This is not true. The reference state has U = 0. Adding 100 J/mol of heat would increase the internal energy to 200 J/mol, unless work was occurring concurrently.
C. Incorrect. This is not true. The reference state has U = 0. Adding 100 J/mol would increase the internal energy to 200 J/mol.
D. Incorrect. This is not true. 100 J/mol is relative to a reference state; it is not a measure of the absolute quantity of kinetic energy contained in the molecules. In addition, internal energy consists of microscopic potential energy as well as kinetic energy.
E. Correct.