## q=∆H clarification [ENDORSED]

Lindsay H 2B
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### q=∆H clarification

Example 8.6 in the book and question 8.31 both ask for a change in energy at (a) constant pressure and (b) constant volume. Does this mean that only part (a) is considered finding the enthalpy, since the enthalpy definition Dr. Lavelle gave us in lecture was the change in heat at a constant pressure?

Chem_Mod
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### Re: q=∆H clarification

Correct.

I will discuss this more in class when we cover: $\Delta U=q+w$

Michelle Dong 1F
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### Re: q=∆H clarification

Constant volume would mean that work (w) equals 0 because of the equation w= external pressure * change in volume. This means that the change in energy at constant volume would only equal q (delta U = q), which is the amount of heat given off or absorbed in a reaction.

Chem_Mod
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### Re: q=∆H clarification  [ENDORSED]

Correct.

To be precise: $\Delta U=q_{v}$

I will cover all of this in class next week.

You are all ahead of the game. :-)