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Difference between delta H and delta U

Posted: Fri Jan 12, 2018 8:04 pm
by Lucia H 2L
What is the difference between delta H and delta U? and q for that matter

Re: Difference between delta H and delta U

Posted: Fri Jan 12, 2018 8:17 pm
by Sirajbir Sodhi 2K
Delta H is the change in enthalpy and Delta U is the change in internal energy. Internal energy is the amount of energy a system has. However, we must realize that a system doesn't exist in a vacuum. Rather, there must be some sort of change in volume/pressure because of the presence of a system. If we hold pressure constant, as it often is when a system is introduced, volume must change (we know this from gas laws). This leads us to the concept of enthalpy which is, in essence, a convenient way to MEASURE a system's internal energy at a constant pressure.

The following equation relates the two quantities:

ΔH = ΔU + PΔV

Q is heat -- and is equal to enthalpy at a constant pressure.

Re: Difference between delta H and delta U

Posted: Sat Jan 13, 2018 4:42 pm
by Sophie 1I
Delta H is the change in enthalpy which is equal to change in U +P*change in V and the delta U is the change in internal energy of the system.
q is the heat of the system.