Approximating

[shaya_smith1F]

In lecture, we went over how we approximate when Kc is small and how we assume that it is just the initial value, would we assume the same for a big Kc?

[Erika Patel 3I]

We can only approximate that the initial and final molar concentrations for the reactants will be the same when Kc is less than or equal to 10^-4. When Kc is larger than this, the change in x will be significant enough that the molar concentration of the reactants at equilibrium will vary from the initial amount. We also only used this approximation in class for a problem with a cubic equation, though I am assuming it would apply for quadratics as well.

[Aisha Randhawa 2G]

When Kc is small, we know that very few products are produced, meaning that the relative decrease in the amount of reactants is a negligible change (which is why we can disregard the x). If Kc is very large, this would mean that a lot of products are produced, meaning that the change in the amount of reactants is quite large, since the reactants are used up quite a bit. Because the change is quite large, I don't think we would disregard x (change) in this case, since it is not negligible.