U vs H

isochoric/isometric:
isothermal:
isobaric:

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vanessas0123
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Joined: Wed Sep 11, 2019 12:17 am

U vs H

Postby vanessas0123 » Thu Feb 06, 2020 4:26 pm

What's the difference between delta U and delta H?

SnehinRajkumar1L
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Joined: Thu Jul 11, 2019 12:15 am

Re: U vs H

Postby SnehinRajkumar1L » Thu Feb 06, 2020 5:48 pm

Delta U is the change in internal energy, whereas delta H is the change in enthalpy. I believe delta H is the total energy change, whereas delta U only accounts for the kinetic and potential energy of a system.

205291012
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Re: U vs H

Postby 205291012 » Thu Feb 06, 2020 10:11 pm

delta U is the change in internal energy versus delta H is the change in enthalpy.

Eva Zhao 4I
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Joined: Sun Sep 29, 2019 12:16 am

Re: U vs H

Postby Eva Zhao 4I » Wed Feb 19, 2020 7:04 pm

To add on, the equation we often use to relate the two is ∆U = q + w. At constant pressure, ∆H = qp. Thus, we can rewrite the equation as ∆U = ∆H - P∆V when pressure is constant.

Chris Tai 1B
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Re: U vs H

Postby Chris Tai 1B » Fri Feb 21, 2020 10:57 pm

Moreover, we can find that deltaU = qv, which makes sense because the volume is constant (no expansion work is being done), so the change in internal energy must solely be a result of the increase of energy inputted into the system qv at a constant volume.
On the other hand, deltaH = qp, which can be derived from the equation relating both deltaU and deltaH. DeltaH = deltaU + PdeltaV, which means deltaH = q+w + PdeltaV. Since w = -PdeltaV, deltaH = q + -PdeltaV +PdeltaV, and since we're assuming that the pressure is constant from qp, we can cancel the last two terms to get deltaH = qp.

Anish Natarajan 4G
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Re: U vs H

Postby Anish Natarajan 4G » Sat Feb 22, 2020 2:15 pm

The change in internal energy is a summation of the enthalpy and the work done on the system so Delta U is Delta H +w

Jesse Anderson-Ramirez 3I
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Joined: Thu Sep 26, 2019 12:18 am

Re: U vs H

Postby Jesse Anderson-Ramirez 3I » Sun Feb 23, 2020 11:28 pm

Delta U is the change in internal energy while delta H is the change in enthalpy.

Leyna Dang 2H
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Joined: Thu Jul 25, 2019 12:17 am

Re: U vs H

Postby Leyna Dang 2H » Sun Feb 23, 2020 11:37 pm

Delta U represents the change in internal energy while delta H represents the change in enthalpy.

Leonardo Le Merle 1D
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Joined: Wed Feb 27, 2019 12:16 am

Re: U vs H

Postby Leonardo Le Merle 1D » Thu Mar 12, 2020 11:29 am

A note on delta U being expressed the change in internal energy; (U=w+q); w is often expressed interchangeably as work done on the system and work done BY the system. For the former, it is w+q; for the latter, it is actually -w+q because the work done by the system is still positive but it results in a decrease in U.

Tanmay Singhal 1H
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Re: U vs H

Postby Tanmay Singhal 1H » Thu Mar 12, 2020 11:38 am

delta u is change in energy delta h is change in enthalpy

Charlene Datu 2E
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Re: U vs H

Postby Charlene Datu 2E » Thu Mar 12, 2020 5:14 pm

Chris Tai 1B wrote:Moreover, we can find that deltaU = qv, which makes sense because the volume is constant (no expansion work is being done), so the change in internal energy must solely be a result of the increase of energy inputted into the system qv at a constant volume.
On the other hand, deltaH = qp, which can be derived from the equation relating both deltaU and deltaH. DeltaH = deltaU + PdeltaV, which means deltaH = q+w + PdeltaV. Since w = -PdeltaV, deltaH = q + -PdeltaV +PdeltaV, and since we're assuming that the pressure is constant from qp, we can cancel the last two terms to get deltaH = qp.


Is this something we are supposed to memorize, or can this be derived from the equations given to us?

aishwarya_atmakuri
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Joined: Sat Jul 20, 2019 12:15 am

Re: U vs H

Postby aishwarya_atmakuri » Thu Mar 12, 2020 6:01 pm

Delta U is change in internal energy, while delta H is change in enthalpy. Under certain conditions, they can be equal to each other.

Naneeta Desar 1K
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Joined: Fri Aug 09, 2019 12:15 am

Re: U vs H

Postby Naneeta Desar 1K » Thu Mar 12, 2020 6:09 pm

Delta U is the change in internal energy whereas delta H is change in enthalpy.

kevinolvera1j
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Joined: Fri Aug 02, 2019 12:15 am

Re: U vs H

Postby kevinolvera1j » Fri Mar 13, 2020 3:06 pm

delta U is change in internal energy whereas delta H is change in enthalpy.

Chris Tai 1B
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Joined: Sat Aug 24, 2019 12:16 am

Re: U vs H

Postby Chris Tai 1B » Fri Mar 13, 2020 8:54 pm

805317518 wrote:
Chris Tai 1B wrote:Moreover, we can find that deltaU = qv, which makes sense because the volume is constant (no expansion work is being done), so the change in internal energy must solely be a result of the increase of energy inputted into the system qv at a constant volume.
On the other hand, deltaH = qp, which can be derived from the equation relating both deltaU and deltaH. DeltaH = deltaU + PdeltaV, which means deltaH = q+w + PdeltaV. Since w = -PdeltaV, deltaH = q + -PdeltaV +PdeltaV, and since we're assuming that the pressure is constant from qp, we can cancel the last two terms to get deltaH = qp.


Is this something we are supposed to memorize, or can this be derived from the equations given to us?


We don't necessarily have to memorize this, but it would be ideal if we understand how to derive it or explain why it is what it is. If we know how to derive the equation, then we'll naturally be able to memorize it over time.

Alfred Barrion 2H
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Joined: Sat Jul 20, 2019 12:16 am

Re: U vs H

Postby Alfred Barrion 2H » Fri Mar 13, 2020 9:06 pm

Delta U is change in internal energy while delta H is a change in enthalpy.


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