Enthalpy is an extensive property. In general,if enthalpy of an overall reaction $A \to B$ along one route is $\Delta_r H$ and $\Delta_r H_1, \Delta_r H_2, \Delta_r H_3, \dots$ represent enthalpies of intermediate reactions leading to product $B$. What will be the relation between $\Delta_r H$ for overall reaction and $\Delta_r H_1, \Delta_r H_2, \Delta_r H_3, \dots$ etc. for intermediate reactions?

• A
  $\Delta_r H = \Delta_r H_1 + \Delta_r H_2 + \Delta_r H_3 + \dots$
• B
  $\Delta_r H = \Delta_r H_1 - \Delta_r H_2 - \Delta_r H_3 - \dots$
• C
  $\Delta_r H = \Delta_r H_1 \times \Delta_r H_2 \times \Delta_r H_3 \times \dots$
• D
  $\Delta_r H = \Delta_r H_1 / \Delta_r H_2 / \Delta_r H_3 / \dots$