Question

the standard enthalpy of combustion of ethane and hydrogen are -1559.7 kJ/mol and -286kJ/mol respectively, while the standard enthalpy of hydrogenation of ethyne to ethane is -296kJ/mol.
Use Hess'ss law to find the enthalpy of combustion of ethyne

Answer 1

ΔH_comb(C₂H₂)=ΔH_comb(C₂H₆)-2ΔH_comb(H₂)+ΔH_hydr(H₂)=-1559.7+(-296)-2(-286)=-1283.7 kJ/mol