enthalpy

[Mariane Sanchez 1E]

so the formula for enthalpy is internal energy + pressure(volume). why is pressure and volume need to be accounted for when calculating enthalpy?

[Merzia Subhan 1L]

Enthalpy is the internal energy plus pressure and volume. Because enthalpy is total potential energy of a system, you have to take into account how external pressure and the volume affect the system.

[Nicole Anisgard Parra 2H]

The enthalpy of a reaction is measured when the reaction is carried out with constant pressure. A calorimeter can ensure that the pressure and volume is held constant. When you measure the energy in the system, it is the internal energy; to convert it to the enthalpy of the reaction, you add the changes in pressure and volume, which in this case would be zero. You must take this into account, but for the most part, in an open system, you can assume the volume and pressure is held constant.