qp and qv

[Cassidy Chiong 2J]

So I understand that qp=deltaH because enthalpy is defined as the amount of heat released or absorbed at a constant pressure. Is there a value we can set equivalent to qv?

[OishiBhattacharya2K]

I know Dr. Lavelle mentioned in lecture that delta U equals qv whenever volume is constant, but I'm a little confused about the concept behind that statement

[Sophie Vikram 1L]

You can set delta U equal to qv.

[Sujin Lim 1H]

Delta U = qv if the reaction is done under constant volume. This is because in constant volume, there can be no volume change no there is no work of expansion. Therefore, w=0, so the equation deltaU = q + w just turns into deltaU=qv where qv is the heat transfer of a system under constant volume.

[505706331]

Delta U = qv if the reaction is done under constant volume. This is because in constant volume, there can be no volume change no there is no work of expansion. Therefore, w=0, so the equation deltaU = q + w just turns into deltaU=qv where qv is the heat transfer of a system under constant volume.

what does delta u mean/stand for?

[arielle_cunanan3K]

Delta U = qv if the reaction is done under constant volume. This is because in constant volume, there can be no volume change no there is no work of expansion. Therefore, w=0, so the equation deltaU = q + w just turns into deltaU=qv where qv is the heat transfer of a system under constant volume.

what does delta u mean/stand for?

delta U stands for the change in internal energy of a system, so the net release or gain of energy for a system

[QUEP 2F]

Hi!

The energy of a closed system can be changed by heating/cooling or compression/expansion, giving us ∆U=q+w. What you’re looking for is ∆U=qv, which is only if volume remains constant in the reaction. Work is defined as P∆V; if the change in volume is zero, work will equal zero, leaving us with ∆U=qv.

[Samantha Quevedo 2L]

What is the difference between qp and qv?

[Joelle Tran 1K]

We can set delta H equal to Qp as well as Qv. It just depends on the situation.

Qv: heat is absorbed/released at constant VOLUME; bomb calorimeter
Qp: heat absorbed/released at constant PRESSURE; coffee cup calorimeter

I think of it as the sub-letter indicating what is constant!

[HemangD 3K]

delta U = Qv + w. When volume is constant, there is no work. Hence, delta U is equal to Qv.

[Phoebe Ko 3E]

Hi, we can set Qv equal to ∆U if the volume of the reaction is constant. ∆U represents the change in internal energy of a system, so the entire equation should be ∆U = q + w. However, since there is no work expansion when the volume remains the same, we can disregard the "w" and derive ∆U = Qv. I hope this was helpful!

[Cynthia_L_2C]

We can set qv=delta u if you know that the volume is constant.

[Sarah Hong 2K]

Delta U is equal to qv when volume is constant because when volume is constant, there is no work being done and w=0. This leaves the delta U equation to simply just equal qv.

[Sidharth Paparaju 3B]

Delta U is equal to qv.

[Ramya_Paravastu_1H]

If the volume is constant, qv=delta u, since in delta u = qv + w, in this case, we know w is 0, since there is no work (volume is constant).

[Aya Watson 2B]

Delta U because there is no work when volume is constant!