ICE

[Ariana Murillo 2O]

While doing practice problems, when do you take the x out of the denominator?

[Jennifer_Lam_1A]

I think you're referring to when approximating x. You omit the x in the denominator just to approximate x. Once you find the x, divide it by the molarity given. If it is smaller than 5%, it is a good approximation. I hope that answers your question!

[EmmaSaid3C]

You can generally take out the x when the k value is less than 10^-5.

[Jeannie_Kim_1I]

If the k value is equal to 10^-5, would we keep the x in the denominator and use the quadratic equation?

[904779609]

You're in the clear to approximate without using x if it is 10^-5, 10^-6 and so on. If it is 10^-3 you leave x and use the quadratic equation. But if it is 10^-4 you can take out x and to be sure you would then check if you're in the 5% range.

[Skolli20]

I also just want to mention what another student told me today at a review session. You can't just blindly approximate if you see the Ka or Kb value is 10^-5. Take the extra 2 minutes and make sure that it is actually 5% because if the initial value is smaller than 10^-5 it will mess up your calculations.