qp and qv

[Diana_Diep2I]

Why is qp=∆H and not qv?

[Abby Soriano 1J]

By definition, enthalpy is the amount of heat absorbed/released at a constant pressure. So that means that delta H only equals qp rather than qv.

[Sjeffrey_1C]

Enthalpy in this case is referring to heat at a specific pressure, not a specific volume. Thus, the p subscript instead of v.

[Hailey Kim 4G]

Enthalpy, which is represented by delta(h), is heat at a constant pressure. Heat is represented by "q", and because the pressure is constant, it will have the subscript "p" for pressure, rather than "v" for volume.

[Daria Azizad 1K]

When volume is not constant, the gas is either expanding or compressing, so there is some work done. Therefore, that energy from work contributes to the delta H and must be factored in.

[Sydney Myers 4I]

It's simply that the definition of enthalpy is heat at a constant pressure. That's how it's defined as a function.

[Junwei Sun 4I]

Because by definition H is the heat transferred at constant pressure.

[Maya Pakulski 1D]

This is because by definition delta H only equals q at constant pressure.

[Orrin Zhong 4G]

If the heat transfer is occurring while pressure is changing, q is not equal to change in enthalpy, since the change in enthalpy is defined at a constant pressure. Therefore, change in enthalpy only equals q when pressure is held constant: qp = change in enthalpy.