# Where are my Chemistry people at?

by RavenPearl 8 Replies latest jw friends

• ##### 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 °C

A 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 / (z-x)

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).