Protonation State

[Jua Ellie Ha 1K]

Hello, how do we find the protonation state of a weak acid using the pKa value?

[Leewon Koo 2K]

When the pH of the solution is equal to the pKa, half of the acid will be protonated and half is deprotonated. This means that if the pH is lower than the pKa, there are more protonated molecules. If the pH is higher that the pKa there are less protonated molecules.

[Anjana Shriram 2A]

Hi! I think you would also need to be given the pH. Then, if the pH < pKa, the solution is already super acidic so the weak acid will remain protonated. If the pH > pKa, then the solution is still alkaline enough that the weak acid will become deprotonated. So:
pH < pKa --> acid exists more in the protonated form
pH > pKA --> acid exists more in the deprotonated form
Hope that helps!