q and delta H

[Lara Almeida 3D]

What is the relationship between q and delta H? Aren't they the same as q is the heat transfer?

[Ashley Hiti 1K]

I think that although delta H and q are related they are not the same because a change in enthalpy is not directly heat transfer. Basically I think of q as being the heat transfer in reactions like heating/melting/etc. while delta h is just the total energy in the system, not specifically "moving" heat.

[Ashley Johnson 2G]

If there is no work done on the system, the change in ethalpy, delta H, will equal the heat transfer of the system, q. But, they are not equal when volume or pressure is changing, and work is being done on the system.

[Jeffrey Yang 3I]

if heat transfer occurs (or q > 0), delta H will have q included in its calculation. However, delta H accounts for all parts of the system (or energy change in energy) which can be internal or external. Q will only occur internally (or from the system to the environment).

[Jason Ho 2L]

q and ∆H are the same only when no work is being done. If pressure or volume changes, then that means work is being done and q does not equal ∆H.

[Mario Prado 1K]

Hello,

q and delta H are the same when no work is being done, but as soon as some form work is being done due to a change in pressure or volume then they are no longer the same.

Hope this helps.