Oxygen at 150 K and 41.64 atm has a tabulated specific volume of 4.684 cm³/g and a specific internal energy of 1706 J/mol. 

(a) The figure 1706 J/mol is not the true internal energy of one g-mole of oxygen gas at 150 K and 41.64 atm. Why not? In a sentence, state the correct physical significance of that figure. (The term “reference state” should appear in your statement.) 

(b) Calculate the specific enthalpy of O₂ (J/mol) at 150 K and 41.64 atm, and state the physical significance of this figure. What can you say about the reference state used to calculate it?