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Our AP Chem class has been given an equilibrium problem using the ICE method. We have worked out the answer, but compared to the supplied "correct answer" are coming up doubled...Can you help us understand where we have gone wrong? PROBLEM: Find the K for the reaction: 2 CO(g) + O2(g) <-> 2 CO2(g) if initially there are 5.0 moles of CO, 10.0 moles of O2, and 1.0 mole of CO2 in a 2.0 L container and at equilibrium CO2 has a concentration of 2.5 mol/L. When working the ICE, we determine that x = 1 which when plugged back into the Kc expression gives us (2.5)squared over [(.5)squared times 4]. This gives us a Kc value of 6.25 but our answer key tells us that the answer should be 3.125. We are wondering, isn't the K value independent of the number of liters, and thus our answer should not be divided by 2? Where are we going wrong? Thanks for your chemical knowledge and willingness to share!
Question Date: 2017-04-06
Answer 1:

I do know that both O2 and CO are pretty reactive, and that CO2 is not, so I would think that the equilibrium would strongly favor the CO2 over the O2 and CO. I don't know how your numbers will work, though.



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