Thermodynamics

[yellowjellybean]

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Can someone help me understand why internal energy is equal to enthalpy at constant volume and pressure conceptually or preferably in terms of the other thermodynamic equations?

 

[Jepstein30]

Can someone help me understand why internal energy is equal to enthalpy at constant volume and pressure conceptually or preferably in terms of the other thermodynamic equations?

deltaE = deltaU + PdeltaV + VdeltaP

So at constant pressure and constant volume, last two terms are 0 leaving

deltaE = deltaU

 

[indianjatt]

Delta U = Q - PDelta V.

If you are at constant volume conditions, the change in volume is zero. Volume isn't changing.

Pressure x delta V = Pressure x 0 = 0

So b/c work = 0.

Delta U = Delta H

 

[sciencebooks]

Delta U = Q - PDelta V.

If you are at constant volume conditions, the change in volume is zero. Volume isn't changing.

Pressure x delta V = Pressure x 0 = 0

So b/c work = 0.

Delta U = Delta H

When is Q = delta H again?