Here's the question from my homework:
At 850K, the value of the equilibrium constant Kp for the ammonia synthesis reaction:
N2(g) + H2(g) N2H2(g)
is 0.2250. If a vessel contains an initial reaction mixture in which [N2]=0.0200M, [H2]=0.0200M, and [N2H2]=.000200M, what will the [N2H2] be when equilibrium is reached?
I know that to find K
c from K
p, we use this equation:
K
p=K
c(RT)
Δn, which becomes .2250=K
c(.08206×850)
-1Solving for K
c, I get K
c=15.694.
Here is the ICE table:
| N2 | H2 | N2H2 |
I | .02M | .02M | .0002M |
C | -X | -X | +X |
E | .02-X | .02-X | .0002+X |
I know that K
c=[N
2H
2]/[N
2][H
2], so plugging in the numbers from row E, I get...
15.694=(.0002+X)/(.02-x)
2This ends up being a quadratic equation, -15.694X
2-1.62776X+.000428=0
When solved, X=2.6227×10
-4 and -0.10398
The root that makes sense is the first one, which would make the ending concentration of N
2H
2 4.6227×10
-4 M.
But...I can't the the computer to accept my answer. I've been over my calculations with a fine toothed comb, and I can't find any errors. (Well, ok, at first I found a bunch of errors, but after fixing them it still won't take it!) If anyone can tell me where I'm going wrong, I would really appreciate it!