Acid Strength

[Victoria Luu - 1C]

How can you determine the strength of an acid through the ka and pka?

[armintaheri]

Ka is the dissociation constant for the acid. The higher the Ka the more completely the acid dissociates. Therefore high Ka corresponds to stronger acid. pKa is the negative log of Ka. So the smaller the pKa the stronger the acid.

[Joanna Pham - 2D]

Strong Acid: Large Ka, small pKa; also means the conjugate base will be weak
Weak Acid: Small Ka, large pKa; also means the conjugate base will be strong

Strong Base: Large Kb, small pKb; also means the conjugate acid will be weak
Weak: Small Kb, large pKb; also means the conjugate acid will be strong

[Jennifer Su 2L]

To add on to the post above, the concept that the stronger the acid, the weaker its conjugate base, and the stronger the base, the weaker the conjugate acid is known as conjugate seesaw. It's also helpful to remember that Ka x Kb = Kw and pKa + pKb = 14.