Homework Help: Chemistry equilibrium Question

1. Feb 5, 2008

erjkism

[SOLVED] Chemistry equilibrium Question

1. The problem statement, all variables and given/known data

K=64. at 25 degrees celsius

N2(g) + 3H2(g) <--> 2NH3(g)

Molarity N2= .5M H2= 1.5M. what are the equilibrium concentrations?

i got the equilibrium table set up, and the K expression is
(2x)(2x)
k= ------------------------------
(.5-x)(1.5-3x)(1.5-3x)(1.5-3x)

how can i solve for x???

2. Feb 6, 2008

Gannon

I'm not sure if you raise the equilibrium concentrations to powers; if not, I have:

K = 2x / (0.5 - x)(1.5 - 3x)
K = 2x / (3x^2 - 3x + 0.75)
(3x^2 - 3x + 0.75)K = 2x
(3x^2 - 3x + 0.75)K -2x = 0
K3x^2 - K3x + K0.75 - 2x = 0
K = 64, so:

192x^2 - 190x + 48 = 0

Plug this into the quadratic equation, then substitute the answer for x for each concentration. For example, since the equilibrium concentration for NH2 is 2x, if x = 4, the equilibrium concentration would be 8M.

Just keep in mind that I'm not sure about raising the terms to stoichiometric powers in this kind of problem...

3. Feb 6, 2008

chemisttree

For equilibrium of a reaction of the type,

$$aA + bB +cC + .... \leftrightharpoons\ dD + eE + ....$$

the equilibrium expression is:

$$\frac{[D]^d[E]^e...}{[A]^a^b[C]^c...}$$

I'm not sure why you are using 'x' in your problem since it really isn't necessary.

Last edited: Feb 6, 2008
4. Feb 6, 2008

erjkism

forget it i found out what to do