Where are my Chemistry people at?
by RavenPearl

RavenPearl
Dude.......i'm like zoning on this. I can't figure it out. I got 1.79 and .11 and .11 ...but Its not working.
Consider the following equilibrium
COBr2(g) ↔ CO(g) + Br2(g) Kc = 0.190 at 73 °C
Consider the following equilibrium:
COBr2(g) ↔ CO(g) + Br2(g) Kc = 0.190 at 73 °CA 3.8 mol sample of COBr2 is transferred to a 2.0 L flask and heated until equilibrium is attained. Calculate the equilibrium concentrations of each species.
[COBr2] = M
[CO] = M
[Br2] = M
And the second part of this is instead of 2L ...it's 1L and I have to find it. Does anyone know this? I'm totally stuck. I did google and ice boxed it and everything and i'm stuck. Any help?

bohm
I know jack shit about chemistry but here goes:
Go to wikipedia:
https://en.wikipedia.org/wiki/Equilibrium_constant
Lets write it as A <> B + C
The initial concentration of A is
[A] = 3.8/2 M/L = z
Then you know that whatever happens
[A] + ([B] + [C])/2 = z and [B] = [C]
so:
[A] + [B] = z
Then looking at wikipedia I guess:
Kc = [B] [C] / [A] = [B]^2 / [A]
Plug in [A] we get
Kc = [B]^2 / [A] = [B]^2 / (z[B])
If we let x = [B] we get:
Kc = x^2 / (zx)
This gives you the 2d poly:
x^2 + Kc * x  z Kc = 0
solving for x gives:
x = [B] = 0.1741
and so
[A] = 1.726
Keep in mind this is just something I am jotting down from wikipedia...

waton
wow bohm.you are booming! make no bones about it!

RavenPearl
First off, wow, dude thank you. You went and actually 'studied' up on it. That's freaking selflessness right there.right on I gotta praise you on that
unfortunately those answers don't work. There are no coefficents for the elements so it can't be squared. ...again awesome job though!

bohm
ah yes that makes sense. So it should probably be:
[A] <> 1/2 [B] + 1/2 [C]
to keep Kc dimensionless and
Kc = [B]^.5 * [C]^.5 / [A]
and same procedure as above can be applied to solve for [B], [A]. Does that make sense?

bohm
The coefficients on wikipedia (sigma, tau, etc. on wikipedia) keeps track of the number of elements. So if you start out with A=1000 of A's in a bottle and they all get made into B's and C's you end up with 1000 of B and 1000 of C. So in general it holds that
A = 1/2 B + 1/2 C
That you divide by volume doesn't change that and so
[A] = 1/2 [B] + 1/2 [C]

LevelThePlayingField
In the JW world, remember, 2+2=5. That's my 2 cents. Oh, and don't mix ammonia and bleach :)

RavenPearl
Thank you all! I appreciate your help. I was able to figure it out. I had to use the quadratic formula in order to get it right. And unfortunately, a slight miscalculation in the 2a portion was changing everything. So Instead of dividing the whole thing by 2am, i was only doing it under the square root!...messed up everything.
Thank you so much guys...i got it =D you guys are awesome!
p.s. ......yes mustard gas sucks

sir82
In the JW world, remember, 2+2=5.
Actually, that's 1 + 1 = 1 (overlapping generation).