This entire section will deal with Brønsted-Lowry acids and bases. In other words, the simple model of HA where the “H” is a proton and the “A” is the base.
When you here the word “conjugate”, it means the product AFTER the proton is donated. The conjugate acid is the newly protonated product; the conjugate base is the leftover “A” AFTER the proton leaves.
The “H” is either strongly bound to the base “A” or loosely bound.
Here’s how to tell:
Protons are more acidic when the conjugate base is more stable.
How can I tell if it is more stable as a conjugate base?
-Electronegativity
-Resonance
ELECTRONEGATIVITY – fancy way to say how evenly electrons are shared in a bond.
Fluorine does not like to share electrons, so HF is a strong acid since F is the most electronegative, but wait…
As the size of the conjugate base becomes larger, the stability of the conjugate base increases. Bromine is a huge atom, so the conjugate base “Br-“ is very stable when compared to “F-“. Therefore, HBr is a stronger acid. The trend continues to HI.
RESONANCE – fancy way to say how evenly electron charge is distributed on a molecule.
You may have heard the term delocalized electrons. Well, that’s electrons that aren’t localized (concentrated) at a single point.
The more you can spread that charge around, the more stable the conjugate base.
Highly recommend practicing these problems: