According to Hess' law, if a reaction can take place by two routes and the starting and finishing conditions are the same, what is true about the total enthalpy change for each route?

Calculate the enthalpy change of formation of C₂H₅OH using the following enthalpy of combustion data:

ΔH^⦵_c(C) = -394 kJ mol^-1

ΔH^⦵_c(H₂) = -286 kJ mol^-1

ΔH^⦵_c(C₂H₅OH) = -1,367 kJ mol^-1

Calculate the enthalpy change of formation of C₆H₁₄ using the following enthalpy of combustion data:

ΔH^⦵_c(C) = -394 kJ mol^-1

ΔH^⦵_c(H₂) = -286 kJ mol^-1

ΔH^⦵_c(C₆H₁₄) = -4,163 kJ mol^-1

Calculate ΔH^⦵_r for the reaction: NH_3(g) + HCl_(g) ➔ NH₄Cl_(s), using the following enthalpy of formation data:

ΔH^⦵_f(NH₃) = -46 kJ mol^-1

ΔH^⦵_f(HCl) = -93 kJ mol^-1

ΔH^⦵_f(NH₄Cl) = -314 kJ mol^-1

Calculate ΔH^⦵_r for the reaction: Fe₂O_3(s) + 3Ca_(s) ➔ 2Fe_(s) + 3CaO_(s), using the following enthalpy of formation data:

ΔH^⦵_f(Fe₂O₃) = -824 kJ mol^-1

ΔH^⦵_f(CaO) = -635 kJ mol^-1

Select the true statement about ΔH^⦵_f values.

What is the value, in kJ mol^-1, of the enthalpy change of formation of an element?