Stupid Chemistry

posted by .

Ok, blonde moment here, Kb is the same as Ka but just for bases and Ka is for acids correct?

right. Ka is the ionization constant for acids, Kb is the ionization constant for bases.
BUT, we can change one into the other this way.
KaKb = Kw.
So if you are given a Ka but you need the Kb for the same acid, KaKb = Kw will convert it for you.

Okay, now that is settled. Thanks. If I'm trying to figure out the pH of a solution and am given the formula for the species, the conjugate acid, and the Kb, do I use the original formula or the conjugate acid formula when I convert to mol/L?

It confusing to answer a question like that. Suppose we want the pH of a solution that is 0.1 M in acetate ion, which I will label Ac^- but you realize it is C2H3O2^- and the acid is HC2H3O2.
We write the hydrolysis equation.
Ac^- + HOH ==> HAc + OH^-
Then Kb (the Ac^- acts as a base) =
[(HAc)(OH^-)/(Ac^-)] = Kb.
Usually we are given the Ka for acetic acid and we do Kb = Kw/Ka and plug in Kb. Ka is the ionization constant for acetic acid, Kb is the base constant for the acetate ion, the conjucate base.

Okay. Thanks. Now, how do I calculate the percent ionization of a reaction. For example, if I have a 0.21 M acid with a Ka of 1.3 x 10^-5, what is the percent ionization. I don't even know where to begin. We've never even discussed a problem like that in class.

I think I went through that earlier although it may have been for another student. Anyway, do you have H^+ and P^- ion? If so then [(H^+)/(HP)] x 100 = percent ionization. It's the same as calculating precent apples in a bag of apples and oranges.
%apples = (#apples)/(total fruit)*100.
%ionization = (amount ionized)/(what we started with)*100.

Oh geez, that's easy. It might have been me and maybe I just wasn't listening. By the way, I LOVE how you are explaining to me how to do this rather than just giving me answers. It really helps, as I am "going back to school" and I am trying to do the best I can at really understanding this stuff.

Thanks. We try to explain the concept and not do the actual homework. It's the concept that you need to understand. You can memorize 100 problems and always be able to do those 100 but no others; BUT you can learn the concept and work thousands just like it.

Respond to this Question

First Name
School Subject
Your Answer

Similar Questions

  1. Chemistry - Acids and Bases

    What's a good example of a balanced neutralization reactions involving strong acids and bases?
  2. Chemistry

    A concept map was to be created on acids and bases. The concept terms that were given to use were: aqueous solution,bases,acids,ions,weak bases, strong bases, strong acids, weak acids,dissociation, weak electrolyte, strong electrolyte,reaction,salt, …
  3. Chemistry

    Your laboratory supervisor directs you to prepare 500.0 mL of a buffer with a pH of 9.40. You have available all the weak acids and bases and the salts of those weak acids and bases. Describe how you could make this buffer.
  4. Chemistry

    Calulate the degree of ionization for NH3(aq) in 1.0 M solution, Kb = 3.236E-4. I've seen degree ionization for acids and not bases. Do I need to find the Ka [H+] value of the base to determine the degree of ionization?
  5. Chemistry

    Need help with AP chemistry, specifically Acids and Bases The acid ionization constant, Ka, for propanoic acid, C2H5COOH, is 1.3  10 -5 . (a) Write the expression for the acid-dissociation constant, Ka for propanoic acid. (b) …
  6. Chemistry

    Determine the direction of the following reaction from the relative strengths of acids and bases: H2S(aq) + C2H3O2-(aq) yields Hc2H3O2(aq) + HS-(aq) The book says this will favor the reactants. I'm confused...shouldn't this be neutral …
  7. Chem

    What simplifying assumptions do we usually make in working problems involving equilibria of salts of polyprotic acids?
  8. Chemistry - Acids/Bases

    What kinds of compounds are typically strong bases?
  9. chemistry

    in our notes for strengths of acids and bases it says that you could add a strong/weak acid with a strong/weak base and it will give you a low, medium or high delta h. so wouldn't acids and bases be related to thermochemistry?
  10. Chemistry - Acid and Bases

    In aqueous solution, classify these compounds as strong acids, weak acids, strong bases, weak bases, or other. HNO3 HBr HF CH3COOH H3PO4 NaOH Ba(OH)2 (CH3)3N NH3 NaCl

More Similar Questions