Achieve Problems 9 and 10

[Maddy Barron 1L]

Hello! Can someone explain why A- is charged and HA+ is neutral? I sort of understand pH=pKA, pH>pKa, and pH<pKA, but extra clarification would help! Thank you in advance!

[Mikayla_Weinhouse_2F]

I believe that pKa is the dissociation of an acid and pH is the acidity or alkalinity of the whole experiment. When pH and pKa are equal to each other it means the concentration of the conjugate acid and conjugate base are also equivalent. I think this means that when the pH increases, so does the proportion of the conjugate base, etc.

Along with this, if you break down pH to H3O+ and pKa into the acid equilibrium expression, with H3O+ and A- on top, and HA on the bottom, you could then solve for what the relationship means. In simpler terms, if pH is greater than pKA, then it is charged because there is more A- than HA, but if pKA is larger than pH then its neutral because it is more stable if it does not dissociate, so there is more HA then A-. I hope that helps!