In the third question, why do you talk about NaHSO4 when the question asks about Na3PO4?
The other answers look right, but the computer may be fussy about format. I wonder about sig figs. Are you meant to assume there is an exact integer number of moles, because there is a whole number of balls? Or are you meant to take it as "to the nearest integer", i.e. (e.g.) 9±0.5 moles? And it gets problematic when you take logs. And be careful with words - the answer to part e, for example, is the word "strong", not the phrase "strong acid".