Textbook question 4.51

[Paige Lee 1A]

Could someone please explain the answers for parts B and C?
Using values in Appendix 2A, calculate the standard Gibbs free energy for the vaporization of water at 25.0 8C, 100.0 8C, and 150.0 8C. (b) What should the value at 100.0 8C be? (c) Why is there a discrepancy?

[Katherine Wu 1H]

b. the value at 100 celsius should be exactly 0, because this is the normal boiling point of water
c. the discrepancy arises because the enthalpy and entropy values calculated from the tables are not rigorously constant with temperature. better values would be obtained using the actual enthalpy and entropy of vaporization measured at the boiling point.