acheive week 10 question 14

[Daljit Takher 1B]

How can we tell that in the reaction the predominant species present at pH 7.10 is charged? Also, what would be the answer if the pH was for instance 1 or 10?

My question is about how A weak base, B ,is ionized forming its conjugate acid ( BH+ )

[Allison Peng 1D]

I think an easier way to think about it is using the henderson-hasselbach equation, where pH = pKa + log [base]/[acid]. Therefore, if pH>pKa, that means there must be more of the base species present in the solution.

[Allison Peng 1D]

Additionally, I think you can also think of it as the half equivalence point of a titration (pH = pKa), where exactly half of the acid reacted to turn into the weak base, and thus their concentrations are equal. Thus, if pH>pKa, that means there is a greater [H3O+] than at the half equilibrium, meaning the reaction from WA to WB proceeds further forward (and thus the concentration of base is higher than that of the acid).