Charged vs neutral acids and bases

[Elise Whitlinger 2I]

In questions 9 and 10 on the Achieve, it asks about weak acids and bases being charged or neutral based on the pKAs given. How do you determine this?

[Ava Tam 2A]

Hi, one can determine this by comparing the pKa to the pH. When the pH is equal to the pKa of the conjugate acid (BH+ in the case of Question 10), there would be equal amounts of the weak base (B) and the conjugate acid. However, since the pH is below the kPa, the charged protonated species of BH+ become predominant in the solution. The opposite happens when pKa is above the pH, in which the neutral species of B become predominant. Similar principles are applied to question 9.