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12-15-2012, 06:20 AM
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njdevsfn95
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Quote:
Originally Posted by Rockies94 View Post
So we were doing the ICE tables in class today, and we get down to the part where you do the equilibrium coefficient. And they did it as x^2/[initial concentration] and disregarded the -x at the bottom. This is poorly written so could someone just explain ICE tables to me. Please.
Equilibrium is a pretty basic concept in the fact the forward reaction will be balanced out by the reverse reaction.

Typically, the equilibrium favors one direction so heavily it allows us to make an assumption that there is very little change in the initial concentrations of reactants.

This assumption just makes things easier to solve because if you utilize the "-x" part and continue the ice chart, you're going to have an x^2 and another x when you get down to the E (or equilibrium values).

That would mean utilization of the quadratic formula to solve for x. This can be a big pain in the ass so an assumption is made to eliminate the "x" because chances are it is SO SMALL that getting rid of it has virtually no effect on the true value of x.

Take a look at this link and example 3 to be exact. http://www.science.uwaterloo.ca/~cch.../eqlbcalc.html

I hope I helped!

I usually show my students the quadratic formula method and then show them the assumption method for the same question. It is no surprise they would rather make the assumption because it makes the calculation so much easier.

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