# Temperature and internal energy question

How can I find the temperature of something if i'm give the internal energy(U), volume(V), and number of moles(N). I thought it'd just be pv = nrt but im not sure what to do with the internal energy or how to use it with pressure. Thanks.

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Andrew Mason
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How can I find the temperature of something if i'm give the internal energy(U), volume(V), and number of moles(N). I thought it'd just be pv = nrt but im not sure what to do with the internal energy or how to use it with pressure. Thanks.
I think you will need more than the internal energy, volume and number of moles even if it is an ideal gas. You will need to know an initial state (ie. P,V, n or V, T, n or P, T, n or P, V, T) and the change in internal energy and volume. This is because the heat capacity of a gas is somewhat temperature dependent so although $dU = nC_vdT$ it is not necessarily true that $U = nC_vT$.

Why not just give us the whole problem and we'll see if we can help you.

AM

It's just a ranking task that says Rank from greatest to least the temperatures of the ideal gases below that contain various amounts of internal energy and vorious number of molecules in various volumes." Each case has different internal energy, number of molecules, and volume.

You need to use the formula U=3/2nkT. It can also be useful in forms like U=3/2NRT and U=3/2PV by using the Ideal Gas Law