Question

The reaction $A \longrightarrow C$ proceeds through two paths I and II as shown below :

The correct relationship between $\Delta H, \Delta H_{1}$ and $\Delta H_{2}$ will be

• A. $\Delta H=\Delta H_{2}-\Delta H_{1}$
• B. $\Delta H=\Delta H_{1} / \Delta H_{2}$
• C. $\Delta H=\Delta H_{1}+\Delta H_{2}$
• D. $\Delta H=\Delta H_{1} \times \Delta H_{2}$

Answer 1

Answer: (C)

According to Hess's law; the total heat change $(\Delta H)$ accompanying a chemical reaction is the same, whether the reaction takes place in one or more steps or follows one or more paths.
Therefore, the correct relation between $\Delta H$ and $\Delta H_{1}, \Delta H_{2}$ will be
$\Delta H=\Delta H_{1}+\Delta H_{2}$