which substances have δhf = 0 kj/mol by definition? select all that apply. o2(g) n(g) h2o(l) br2(l) fe(s)…

which substances have δhf = 0 kj/mol by definition? select all that apply. o2(g) n(g) h2o(l) br2(l) fe(s) he(g) done

which substances have δhf = 0 kj/mol by definition? select all that apply. o2(g) n(g) h2o(l) br2(l) fe(s) he(g) done

Answer

Brief Explanations:

The standard enthalpy of formation ($\Delta H_f$) of an element in its standard state is defined as 0 kJ/mol. Oxygen gas ($O_2(g)$) is the standard - state form of oxygen, bromine liquid ($Br_2(l)$) is the standard - state form of bromine, iron solid ($Fe(s)$) is the standard - state form of iron, and helium gas ($He(g)$) is the standard - state form of helium. Nitrogen in its standard state is $N_2(g)$ not $N(g)$, and the standard state of hydrogen and oxygen combined is $H_2O(g)$ not $H_2O(l)$.

Answer:

A. $O_2(g)$ D. $Br_2(l)$ E. $Fe(s)$ F. $He(g)$