posted by Lena on .
0.500 mol of SO2, 0.100 mol of O2 and 0.700 mol of SO3 re intorduced simutaneously into a 1.00 L vessel at 1000 K. For the equillibirum, 2SO2 (g) + O2(g) <---> 2SO3(g), the value of Kc at 1000K is 280. Show mathemtically that the mixture is NOT at equillibrium.
This is what I did:
Kc = [0.700]^2/[0.500]^2[0.100]
Therefore the mixture is not a equillibrium because in order to be at equallibrium, the mixture must have a Kc value of 280.
Did I do this correctly?
Looks good to me. Can you look at the 19.6 versus 280 and say that the reaction will proceed to the left or to the right?
that is the second part of the question; figuring out whether the reaction will move to the left or right. Im not too sure how to figure that out.
is the 1000 k, 1000 kelvin? :S
Yes, 1000 K is 1000 Kelvin.
For part b, look at the Kc expression you wrote first.
Kc = (SO3)^2/(SO2)^2(O2) = 280
Now look at the expression and ask yourself this. To get a smaller number than 280 (in this case 19.6), will the numerator get larger or smaller and will the denominator get larger or smaller. Well, the ONLY way to get a smaller number than Kc is for the numerator to become smaller and/or the denominator to become larger (or both). That tells you which direction the reaction must go.
I want to turn the 19.6 into 280 and in order to do that I must make the numerator larger and the numerator is the SO3 so therefore the reaction will move to the left?
Your reasoning is superb but the answer is not. Here is the reaction.
2SO2 + O2 ==> 2SO3
So you want 19.6 to become larger (to 280). You are correct on that point. To turn the number into a larger number you want the numerator (SO3) to get larger (you are correct) and you want the denominator to get smaller (you are correct there). So now look at the equation. You want SO3 to get larger, you want SO2 and O2 to get smaller, the ONLY way it can do that is to shift the reaction to the right for that is the only way SO2 and O2 are used up(making them smaller) and SO3 is formed (making it larger).
Ohh. I understand now. Thank you so much :)