Thermochemistry: Understanding Delta H and Work in Constant Pressure Reactions

[ace123]

1. For a certain reaction at constant pressure, delta U= -72 KJ, and 39KJ of expansion work is done by the system. What is delta H for this process.

2. I basically have no idea what to do because it's not in my textbook and my professor has never taught this. Maybe If I knew what the delta U stood for I could understand it.

Thanks

Edit: Wild guess, answer is -111 KJ?

 

[ace123]

Anybody know what the damn delta U supposed to signify

 

[Astronuc]

Does this look familiar?

$$\Delta{H}\,=\,\Delta{U}\,+\,P\Delta{V}$$

http://hyperphysics.phy-astr.gsu.edu/hbase/thermo/firlaw.html#c2

 

[ace123]

No, It does not. In my book this is the only way this is written $$\Delta{H}\,=\,\Delta{E}\,+\,P\Delta{V}$$ My guess was that it stood for E but i wasnt sure. Does that I am right?

 

[eli64]

No, It does not. In my book this is the only way this is written $$\Delta{H}\,=\,\Delta{E}\,+\,P\Delta{V}$$ My guess was that it stood for E but i wasnt sure. Does that I am right?

yes, some places use U and some use E, they are the same

 

[ace123]

Okay, Thanks

Edit: Are you stalking my posts eli64 :rofl: