Enthelpy so commonly described only in constant pressure situations?

[pivoxa15]

Why is enthalpy so commonly described only in constant pressure situations? It applies to change in pressure environments as well.

 

[lalbatros]

It is just a matter of taste: choosing what makes a balance simple or choosing to write a little longer balance equation.

The enthalpy can be related to other thermodynamic potentials.
It was probably defined to make things simpler. Try to re-write all the thermodynamics without the enthalpy or without the Gibbs free energy, you will see that some chapters will grow in page number and will be much less readable. That's all, I think.

When pressure is kept constant, work or heat can be accounted directly in terms of enthaply variations.
If pressure is not kept constant, you can still use enthalpy in the accounting but you will need to include not only the effect of work or heat but also the effect of pressure variation.

 

[astrokreng]

Enthalpy is a thermodynamic property that describes the total energy of a system, including both its internal energy and the work done by or on the system. It is commonly described in constant pressure situations because in these scenarios, there is no work being done on or by the system, and therefore the change in enthalpy is equal to the change in internal energy. This simplifies the calculations and makes it easier to analyze the system.

However, enthalpy also applies to change in pressure environments. In these situations, work is being done on or by the system, and thus the change in enthalpy is not equal to the change in internal energy. Instead, it includes the work done by or on the system, which can be calculated using the pressure-volume work equation. Therefore, enthalpy is a useful concept in both constant pressure and change in pressure situations.

The reason why enthalpy is commonly described in constant pressure situations is because many chemical and physical processes occur at constant pressure, such as reactions in open vessels or reactions in a solution. In these cases, the change in enthalpy can be directly measured or calculated using the heat released or absorbed by the system. This makes it a convenient and practical way to analyze these processes.

In conclusion, while enthalpy is commonly described in constant pressure situations, it is applicable in all scenarios, including change in pressure environments. Its usefulness and simplicity in constant pressure situations make it a commonly used concept in thermodynamics.