# How does the Enthelpy change tell us about the stability of the product?

• Frigus
In summary, the video being discussed is imprecise in its explanation of enthalpy change and heat exchange. It also does not mention the important concept of heat of formation and incorrectly states that an enthalpy decrease is a criterion for stability of products. The speaker's explanation is not recommended for students due to its low quality.

#### Frigus

At constant pressure Enthalpy change is equal to heat exchange and we say that "if Enthalpy Change is negative then product formed is stable",
I am not able to make sense of this statement as change in Enthalpy tells us only about heat exchange but internal energy is function of both Work and Heat.
what if work done on the system is more than the heat released?

Hemant said:
At constant pressure Enthalpy change is equal to heat exchange and we say that "if Enthalpy Change is negative then product formed is stable",
I am not able to make sense of this statement as change in Enthalpy tells us only about heat exchange but internal energy is function of both Work and Heat.
what if work done on the system is more than the heat released?
Please provide a reference for that statement.

BvU
Chestermiller said:
Please provide a reference for that statement.

It is also Written it in my notes which are recited by my teacher.

Hemant said:

It is also Written it in my notes which are recited by my teacher.

With all due respect to your teacher and to this video, they are incorrect.

I have very big problems with this video, because it is extremely imprecise with its explanation (which demands being precise). For example, it does not say that the heat of formation is the amount of heat that has to be added to hold the system at the same temperature as it was initially. Clearly, this is pretty important, but it is omitted. If fact, at some point he even says that the system is adiabatic (which it is not).

Enthalpy decrease is not a criterion for stability of the products relative to the reactants. The correct criterion is a decrease in Gibbs free energy between reactants at the specified temperature and pressure and products at the same temperature and pressure. Even this is a rough rule of thumb.

In my view, this video should never be shown to students because of its low quality. Shame on the speaker.

Last edited:
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