### internal energy

Posted:

**Wed Jan 29, 2020 10:26 am**When a question asks what is the change in the internal energy of a reaction, what are they asking you to find? Are they asking for the work?

Created by Dr. Laurence Lavelle

https://lavelle.chem.ucla.edu/forum/

https://lavelle.chem.ucla.edu/forum/viewtopic.php?f=76&t=57622

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Posted: **Wed Jan 29, 2020 10:26 am**

When a question asks what is the change in the internal energy of a reaction, what are they asking you to find? Are they asking for the work?

Posted: **Wed Jan 29, 2020 3:00 pm**

Internal energy is represented as so depending on the question and what values are given, you would use the equation (or its variants) = q + w.

Posted: **Wed Jan 29, 2020 3:10 pm**

Also another derivation of the formula we learned in class today was DeltaU=DeltaH-P(DeltaV) if the pressure is constant.

Posted: **Wed Jan 29, 2020 4:45 pm**

Veronica_Lubera_2A wrote:Also another derivation of the formula we learned in class today was DeltaU=DeltaH-P(DeltaV) if the pressure is constant.

And if the volume is constant, work is equal to 0 because the DeltaV in the work term is 0. So, in that case, DeltaU = q

When a question asks you to find change in internal energy, they are asking you to find DeltaU, and depending on the conditions given in the questions, the calculation of it will be different. In general, it is given by DeltaU = q +w

Posted: **Wed Jan 29, 2020 8:52 pm**

Internal energy, U, is a state property and functions from its final and initial states. For example, if a closed system is changed by heating (+q) and compression (+w) then the equation for internal energy is: delta U = q + w. If volume is constant, delta U = q(v).