WHAT IS HESS LAW?
Hess’ Law can be difficult to understand because of all the big words like enthalpy change, heat summation, state function, etc. Here’s a short video clip to help understand the basics of Hess’ Law before diving into the deep!
Energy change in a system is also called enthalpy change. It is the heat absorbed or given off during a chemical reaction.
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Hess’ Law states that the heat evolved or absorbed in a chemical process is the same whether the process takes place in one or in several steps.
So, in other words, Hess law states that the enthalpy change in a chemical reaction is the same overall whichever route you take. If you want to convert reactants A into products B, the enthalpy change is the same whether you take one step or several steps to achieve that.