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Chemistry Forums for Students => Analytical Chemistry Forum => Topic started by: Wienerbroed on July 07, 2021, 12:11:32 PM

Title: Is it reasonable to derive this formula?
Post by: Wienerbroed on July 07, 2021, 12:11:32 PM

I need to calculate the change in internal energy of a reaction.

Is it reasonable to derive the formula ΔU = ΔH - P * ΔV to ΔU = ΔH - nRT?

In this case the pressure is constant, meaning ΔH = q. All terms should then have the unit joules.
I don't have a measurement for the volume.

Title: Re: Is it reasonable to derive this formula?
Post by: Orcio_87 on July 07, 2021, 01:27:53 PM

True, as pΔV = Δn RT.

Title: Re: Is it reasonable to derive this formula?
Post by: Borek on July 08, 2021, 02:49:22 AM

Quote from: Orcio_Dojek on July 07, 2021, 01:27:53 PM

True, as pΔV = Δn RT.

n and Δn are not synonyms.

Title: Re: Is it reasonable to derive this formula?
Post by: Orcio_87 on July 08, 2021, 03:41:20 AM

Right, I hope that Wienebroed sees the difference in his equation.