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Topic: Equilibrium Concentrations  (Read 4208 times)

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Offline tanner.e

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Equilibrium Concentrations
« on: March 25, 2010, 06:07:47 PM »
Ke = (14.00 + x) / (4.00 - 2x)^2 = 1.75

I understand how to get all this information,  but then I have to find x. Which x = 0.57

Im just confused on how to get x.

Thank you.

quadratic formula, cross multiplication? Any explanations would be very helpful.

Offline Matias Ekstrand

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Re: Equilibrium Concentrations
« Reply #1 on: March 26, 2010, 01:20:01 AM »
You can apply many methods to solve a quadratic equation, so you may want to rearrange your equation to this form:

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Offline tanner.e

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Equilibrium Reaction
« Reply #2 on: March 27, 2010, 02:24:30 PM »
A(g)(g)   ::equil:: 2B(g) +C(g)

When 1.00 mol of A is placed in a 4.00 L container at temperature t, the concentration of C at equilibrium is 0.050 mol/L. What is the equilibrium constant for the reaction at temperature t?

I've been able to solve questions like this when I've been given Ke or the concentrations. Now I'm stuck because I'm given 1 mol and the amount of the container.  How do I find the initial concentration of A and B.  I've been using the I.C.E method so once from there I can calculate this problem its just getting to that point I'm confused.

I've been looking online also and I've found this info.
 C = 0.050 mol/L x 4.00L = 0.2L /4.00L = 0.05 (+x)     and this I understand its from there finding B and A?
 
Next I would guess to solve B. B being two parts of A does this mean I would just multiple 0.05 by 2. which then I would get 0.10(+2x)
So really I guess I just need help solving for A.

Thank you

Offline Matias Ekstrand

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Re: Equilibrium Reaction
« Reply #3 on: March 27, 2010, 02:43:23 PM »
A(g)(g)   ::equil:: 2B(g) +C(g)

When 1.00 mol of A is placed in a 4.00 L container at temperature t, the concentration of C at equilibrium is 0.050 mol/L. What is the equilibrium constant for the reaction at temperature t?

I've been able to solve questions like this when I've been given Ke or the concentrations. Now I'm stuck because I'm given 1 mol and the amount of the container.  How do I find the initial concentration of A and B.  I've been using the I.C.E method so once from there I can calculate this problem its just getting to that point I'm confused.

You have an amount of substance and a volume. This means you can calculate the initial concentration of A. During the reaction you describe, the concentration of A will drop with x. The concentration of B will increase with 2x and the concentration of C will increase with x.

You may calculate x by comparing the initial concentration of C and the equilibrium concentration of C. Read the question once more and you will see that the initial concentration of B and C is zero. To calculate K-values, you need to know equilibrium concentrations, not initial concentrations.
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