Hey Belinda, it’s ok, ask as much as you need.
“HA” is a general term for acid. The “H” represents H+ that the acid can donate, and “A” stands for acid.
“AHA” stands for α-Hydroxy acids (or alpha hydroxy acid). AHAs are a group of acids with a similar molecular structure – they all are carboxylic acids with a hydroxyl group (OH) on the adjacent carbon. Citric acid is an AHA. You already know how to calculate the amount of citric acid you’ll need to reach a specific pH. The same calculation goes for any other acid. It won’t work though if you mixing several acids together. The calculations in this case get much complicated. So if you want to add several acids to water, I suggest testing manually their pH with a pH paper and diluting with water to make a solution less acidic.
