Hess’s Law - Practice Questions & MCQ

Hess's Law

This rule is a consequence of the Enthalpy or Internal energy being a state function.

According to Hess's Law, "The enthalpy change for a process is independent of path or way of a process. The enthalpy change (H or E for any physical or chemical process remains the same whether process is carried out in one step or in many steps. "

Let us consider the following example

Hence it proves that

• H or E is not proportional to path or way of reaction
• H or E is a state function that depends only on the initial and final state (state function).

Applications Hess Law  It has the following applications:

1. It helps in finding enthalpy changes for those reactions also which are experimentally not possible.

2. It also helps in finding  etc.

3. For the determination of resonance energy and lattice energy. 

4. For the determination of enthalpies of reactions occurring very slowly.