Calculate the standard enthalpy change for the formation of acetylene (C₂H₂) from the following data:
a. ΔHf of C₂H₂ = -110 kJ/mol
b. ΔHf of H₂ = -74.8 kJ/mol
c. ΔHf of C(graphite) = 0 kJ/mol
d. ΔHf of HCl = -92.3 kJ/mol