Acid and Base Strength

[Chels Zh 1D]

What is the relationship between pKa and the acid strength, and the relationship between pKb and the basic strength?

I have trouble understanding this explanation in the answer-key book.

Thanks, someone who can help me explain it!! :))

[Sarah_Wilen]

A strong acid means an acid that is able to 100% ionize into its ions. Ka is the acidity constant, which is the ratio of the concentration of the reactants to the concentration of the products to the power of their stoichiometric coefficient. If the Ka constant is on the higher size, we know that the acid strength is great. We know this because a higher Ka constant means that there was a lot of product. If the concentration of product is high, we can tell that the acid ionized a lot, therefore, the acid is strong. If the Ka constant is lower, then the acid is not as strong.

Same goes for the base and its Kb. A strong base is a base that is able to 100% ionize in water. If the Kb is high, then the base is strong. If the Kb is low, then the base is not as strong.

As of their relationship together, Ka and Kb are inverse of each other. As Ka increases, Kb decreases, so as acid strength increases, base strength decreases and vice versa. You can tell this by the relationship: Ka x Kb = Kw (where Kw is the water constant of 1.0 x 10^-14.