Brønsted-Lowry acid base theory (article) | Khan Academy
Here's the key principle: The order of base strength is the inverse of acid strength. The weaker the acid, the stronger the conjugate base. Relative strength of an acid and its conjugate base and relative strength of a In introductory chemistry courses, this relationship is usually expressed in the. Chem 2 - Acid-Base Equilibria VII: Conjugate Acid/Base Pairs and Relationships Between Ka, Kb, and Kw.
Strength of conjugates[ edit ] The strength of a conjugate acid is directly proportional to its dissociation constant.
Strength of Conjugate Acids and Bases Chemistry Tutorial
If a conjugate acid is strong, its dissociation will have a higher equilibrium constant and the products of the reaction will be favored. The strength of a conjugate base can be seen as the tendency of the species to "pull" hydrogen protons towards itself. If a conjugate base is classified as strong, it will "hold on" to the hydrogen proton when in solution and its acid will not dissociate.
On the other hand, if a species is classified as a strong acid, its conjugate base will be weak in nature. An example of this case would be the dissociation of Hydrochloric acid HCl in water. Similarly, if an acid is weak, its conjugate base will be strong. Therefore, weak acids will have weak conjugate bases, unlike the misconception that they have strong conjugate bases. Identifying conjugate acid-base pairs[ edit ] The acid and conjugate base as well as the base and conjugate acid are known as conjugate pairs.
When finding a conjugate acid or base, it is important to look at the reactants of the chemical equation. In this case, the reactants are the acids and bases, and the acid corresponds to the conjugate base on the product side of the chemical equation; as does the base to the conjugate acid on the product side of the equation.
Conjugate acid-base pairs (video) | Khan Academy
We apply the following principle to acid-base reactions: A stronger acid will tend to react with a stronger base to produce a weaker acid and a weaker base. The question is, how do we determine base strength? Draw out the conjugate bases of the acids on your pka table by removing a proton. The order of base strength is the inverse of acid strength.
The weaker the acid, the stronger the conjugate base. Using this principle, you can also use the pKa table to give you the strengths of bases.
I call this the inverse pKa table. Find the acid on the pKa table.
Find the base on the inverse pKa table. Do the acid base reaction — that is, add a proton to the base and remove a proton from the acid. Is the new acid stronger or weaker? Is the new base stronger or weaker?
So CH4 is the acid and HO - is the base in this reaction. Doing the proposed acid base reaction, we transfer a proton from CH4 to HO.
How to Use a pKa Table
The products of this reaction would therefore be CH3 - and water. Now we ask the question — how do these compare in strength to our starting acids and bases? Our product is a stronger acid. Our product is a stronger base. We need to go to a weaker acid-base pair see 2, above.