(Note That Some of These Are the Same Problems as Found

Multiple Choice

(Note that some of these are the same problems as found in the section headed Enthalpies of Atom Combination. However in this section all problems are worked using Enthalpies of Formation.)
-For which of the following substances is the enthalpy of formation, $\Delta$ H_f°,
Equal to zero?

A) H₂(g)
B) H₂O(g)
C) O₃(g)
D) H(g)
E) Na(g)