ΔH of formation Thermochemistry?

For which of the following is the enthalpy of formation, ΔHfo=0? The Enthalpy of formation of elements in their standard state is 0 kJ/mol. (more than one is correct) a. O2(g) b. O c. N2(g) d. H2O(l) e. Na(s) f. Fe(s) g. NH3(g) h. C (diamond state) graphite... show more For which of the following is the enthalpy of formation, ΔHfo=0?
The Enthalpy of formation of elements in their standard state is 0 kJ/mol.
(more than one is correct)
a. O2(g)
b. O
c. N2(g)
d. H2O(l)
e. Na(s)
f. Fe(s)
g. NH3(g)
h. C (diamond state)
graphite state is more stable at STP (standard pressure and temperature)

For which of the following reactions is the enthalpy change in the reaction, ΔHrxno, equal to ΔHfo for NH4OH(s)?

The ΔH of formation is the heat released or absorbed during the formation of a pure substance from its elements, at constant pressure.

Thus, the Enthalpy of formation of a compound is given by the reaction where all the reactants are elements in their standard state and the product is the desired compound.
a. N + 5H + O → NH4OH(s)
b. N(g) + 5H(g) + O(g) → NH4OH(s)
c. 0.5N2(g) + 1.5H2(g) + H20(l)→ NH4OH(s)
d. 0.5N2(g) + 2.5H2(g) + 0.5O2(g) → NH4OH(s)
e. N2(g) + 5H2(g) + O2(g) → 2NH4OH(s)
f. NH3(g) + H20(l)→ NH4OH(s)
2 answers 2