 Physics Help Forum Can't figure out whats wrong with these calculations (Thermal equilibrium)
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 General Physics General Physics Help Forum Dec 2nd 2017, 01:14 AM #1 Junior Member   Join Date: Dec 2017 Posts: 1 Can't figure out whats wrong with these calculations (Thermal equilibrium) Hi. I have the following problem and I just can't figure out whats wrong with my calculations. Problem: You have 2 gasses in a container. Gas A is 2.0g of helium at 300K tempature. Gas B is 8.0g of nitrogen at 600K tempature. 1. Calculate the thermal energies of gasses at initial position. 2. Calculate thermal energies of gasses at thermal equilibrium 3. How much heat is transfered and to what direction 4. What is the final temperature of gasses at thermal equilibrium. My calcs: $\displaystyle n_a=\frac{2.0g}{4g/mol}=0.5mol , n_b=\frac{8.0g}{14g/mol}=0.57mol$ 1. $\displaystyle E_{th(a)}=\frac{3}{2}*n*R*T=\frac{3}{2}*(0.5mol)*( 8.31J/mol*K)*(300K)=1869.75J$ $\displaystyle E_{th(b)}=\frac{5}{2}*n*R*T=\frac{5}{2}*(0.57mol)* (8.31J/mol*K)*(600K)=7105.05J$ 2. $\displaystyle E_{f(a)}= \frac{n_a}{n_a+n_b}*E_{tot} = \frac{0.5}{0.5+0.57}*8974.8J=4193.83J$ $\displaystyle E_{f(b)}= \frac{n_b}{b_a+n_b}*E_{tot} = \frac{0.57}{0.5+0.57}*8974.8J=4780.97J$ 3. $\displaystyle Q_1=E_{f(a)}-E_{th(a)}=4193.83J-1869.75J=2324.08J$ $\displaystyle Q_2=E_{f(b)}-E_{th(b)}=4780.97-7105.05J=-2424.08J$ 4. Now this is where I have my problem. $\displaystyle \Delta$$\displaystyle T_a$=$\displaystyle \frac{Q_1}{\frac{3}{2}*n*R}=\frac{2324.08J}{\frac{ 3}{2}*(0.5mol)*(8.31J/mol*K)}=372.897K$ Now this would indicate that Gas A has higher final temperature than Gas B which just can't be possible, so something is wrong here but I can't just figure out what.  Tags calculations, equilibrium, figure, thermal, wrong Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post Adesinapaul Physics 0 May 25th 2012 01:24 AM whmische Light and Optics 3 Dec 21st 2011 02:05 AM bradycat Energy and Work 1 Nov 29th 2010 09:14 PM rebghb Advanced Thermodynamics 1 Apr 26th 2010 04:46 PM cerberus Energy and Work 1 Jul 29th 2009 05:30 PM