Problem 69 - Chemistry: An Atoms-Focused Approach

Question

How is Hess's law consistent with the law of conservation of energy?

Step-by-Step Solution

Answer

Answer: Hess's Law is consistent with the law of conservation of energy as both are based on the principle that energy cannot be created or destroyed and is conserved throughout a reaction. Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of whether the reaction occurs in one or multiple steps, while the law of conservation of energy maintains that energy is only converted from one form to another. By summing up the enthalpy changes for each step in a reaction, we can determine the total energy change, which remains constant and doesn't depend on the path taken in the reaction. This conservation of energy during chemical reactions is at the core of both Hess's Law and the law of conservation of energy.

Step 1: Understanding Hess's Law

Hess's Law states that the total enthalpy change for a chemical reaction is the same, regardless of whether the reaction occurs in one step or multiple steps. In simpler terms, the enthalpy change for a reaction is equal to the sum of the enthalpy changes for each step in the reaction.

Step 2: Understanding the law of conservation of energy

The law of conservation of energy states that energy cannot be created or destroyed; it can only be converted from one form to another. For example, in chemical reactions, some bonds are broken while others are formed, and the energy involved in these processes is either absorbed or released by the system.

Step 3: Seeing the connection between Hess's Law and the law of conservation of energy

Both Hess's Law and the law of conservation of energy are based on the concept that energy is conserved in any process or reaction. When applying Hess's Law, we take into account the enthalpy changes of all the individual steps of the reaction, and the sum of these changes represents the total energy change for the reaction as a whole. This is in line with the conservation of energy concept, as the total energy change is not varying but is just being redistributed between different steps of the reaction.

Step 4: Conclusion

Hess's Law is consistent with the law of conservation of energy as it also follows the principle that energy cannot be created or destroyed and is conserved throughout a reaction. By summing up the enthalpy changes for each step in a reaction, we can determine the total energy change, which remains constant and doesn't depend on the path taken in the reaction. This conservation of energy during chemical reactions is at the core of both Hess's Law and the law of conservation of energy.