✔ 最佳答案
Enthalpy change for bond breaking
= +(E[C-H]×4 + E[Cl-Cl]×2)
= +(410×4 + 244×2) kJ
= +2128 kJ
Enthalpy change for bond formation
= -(E[H-Cl]×2 + E[C-H]×2 + E[C-Cl])
= -(431×2 + 410×2 + 340×2)
= -2362 kJ
Enthalpy change for the reaction, ΔH
= (+2128 - 2362) kJ
= -234 kJ