Achieve W2 Problems 9&10

[Nataly Antonova 1B]

I was having trouble understanding the concept of charged and uncharged species in problems 9 and 10 of this week's Achieve. While the solution only suggests a more mechanical approach (aka memorization), I was wondering if anyone could explain to me what exactly is going on. Is there a more intuitive way to derive the right answer without having to memorize the relationships?
Thank you!

[Caitlin_Tang_Dis3H]

So for problems 9&10, look at the pH and pKa.

For a base
If the pH < pKa then the charged species (HB+) will be dominant in the solution. If the pH>pKa then the neutral species (B) will be dominant in the solution. If the pH = pKa then the charged and neutral species are of the same amount.

For an acid
If pH < pKa then the neutral species (HA) will be dominant. If pH > pKa then the charged species (A-) will be dominant. If pH = pKA then charged and neutral species are of the same amount.