Delta U equations

Fayola Obasi 1F · Postby **Fayola Obasi 1F** » Mon Feb 06, 2023 3:38 pm

A few classes ago professor gave us the two equations: delta U = qp - P deltaV and delta U = delta H - deltanRT. Can someone explain how these both equal delta U. And how we know which one to use.

Chem_Mod · Postby **Chem_Mod** » Wed Feb 08, 2023 3:43 pm

Please use the equation editor - this was confusing to read... :0

We know:

$\Delta H = \Delta U +P\Delta V$

At constant pressure, $\Delta H_{sys} = Q_{p}$ , so:

$Q_{p} = \Delta U +P\Delta V$
$\Delta U = Q_{p} -P\Delta V$

If ideal gas is assumed, $P\Delta V = \Delta nRT$ , so:

$\Delta U = Q_{p} -P\Delta V$
$\Delta U = Q_{p} -\Delta nRT$

Depending on what your known and unknown variables are, you need to choose which version is appropriate.

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Delta U equations

Delta U equations

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