ideal gas

[cathliccat]

I have the question, "Heat is added to an ideal gas at 20 degrees C. If the internal energy of the gas increases by a factor of three - what is the final temperature (in degrees C) round off to the nearest whole number?"

I know U=3/2NkT or U= 3/2nRT
I see I have 3U and I need to convert 20 degrees C to 293.15K, all the other units are the same. I know k = 1.38 X 10^-23 and somewhere it says what R is. I thought if I set the same equation = to each other I could get the answer, 3(3/2 * k * T)= 3/2 * k * T, but I'm not getting anything feasible. What am I doing wrong? Any help is appreciated!

Thanks,
Carissa

[Norman]

In U=3/2nKT, only T is a variable, all other quantities are constant. So if U~T, is you triple the internal energy what happens to T? Well if 3/2nK is a constant, the number of molecules doesn't change so this should be true, what happens to T? That is the question you should be asking yourself.
Cheers,
Ryan