Question

If the Ka of a conjugate acid is known, which other parameter can be determined?

A. Ka of the strong base
B. Ka of the strong acid
C. Kb of the weak acid
D. Kb of the weak base

Answer 1

@JoannaBlackwelder A or B?

Answer 2

What do you think? It's only one answer.

Answer 3

When an acid is deprotonated or dontates a proton, that is \(\sf -H^+ \) the remainder is called conjugate base. Typically, a strong acid's conjugate base is relatively stable, which means it is a weak one. Now, the same kind of concept applies in terms of conjugate acid.

Answer 4

D is correct becouse the conjugate acid comes from base .with base you will use Kb not Ka

Answer 5

I don't think the answer is d... Remember this that the Kw=(Ka)(Kb) given the known Ka of the conjugate weak acid we can take it and find the Kb of the strong conjugate base like this Kw/Ka=Kb

Answer 6

You are correct , but there is nothing mensioned bout Kb, in this question, of strong base .it just mensioned kb of weak base

Answer 7

Yeah kW = Ka x Kb I always get mixed up with the terminology.. "The Ka of a conjugate acid is known"

If you know Ka you can get Kb that's for sure.

If it's a strong base high Kb it will want that proton badly, I think it would produce a weak conjugate acid w Low Ka.

I guess we don't know whether the base was strong of weak to begin with..

Answer 8

Ok so why isn't it D?

Answer 9

from my understanding whether you are given a \(\sf K_a~or~K_b \) it provides you the information of the other. The a and b are just an assignment for acid and base specifically. An acid's relative strength or weakness provide an information about it's conjugate base. Similarly, a conjugate acid will provide you the relative strength strength or weakness of the base. I think this problem is more about the terminology rather than the qualitative (strong or weak) or quantitative aspect of acid-base. So, if we have to choose from the options provided only considering the assignment of an "a" and "b", then we are looking for a description of base, and the best that will fit is base with a measurement of "b." I would like to read other reasoning if what I provided isn't good to answer the problem.

Answer 10

That is to say that I agree with photon dude

Answer 11

If you have NH3 as a bas . NH4 will be it is conjugate acid .so if I know the Ka of NH4 I will apply
Kw=Ka ×Kb . Ka will be for NH4 becouse it is acid (conjugate acid) while Kb for NH3 becouse its base. NH 3 is a weak base so the answer is (Kb of the weak base)