Oxygen at 150 K and 41.64 atm has a tabulated specific volume of 4.684 cm3/g and
ID: 1053499 • Letter: O
Question
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?
Explanation / Answer
a) Internal energy is not absolute, not relative. It is expressed with reference to normally0deg.c temperature and 1 atm pressrue also known as standard conditions of temperature and pressure. Since the correct temperature is 150K, enthalpy is expected to be -ve with respect to standard temperature and pressure.
b) H= U+PV
speciific volume = 4.684 cm3/gm =149.888 cm3/gmoles = 149.888*10-3J/gmoles
H= 1706+41.64*149.888*10-3 *101.3Joules =2428 joules/mol
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