What is pH?
pH is a measurement of how much H3O+ is in an aqueous solution.
It starts with a measurement of moles per liter ( molarity, M ) of H3O+ in an aqueous solution.
If the molarity of H3O+ in a solution is 10-3M then the pH of the solution is simply 3.
If the molarity of H3O+ in a solution is 10-9 then the pH of the solution is 9.
[H3O+] x [OH-] = 10-14 So when pH is 7 there are equal amounts of H3O+ and OH-.
A high pH, like pH 10, would mean the M of H3O+ in the solution is 10-10, which is a smaller number than say 10-4.
So, a low ( lower than 7 ) pH has more H3O+ in it than HO-. So a low pH, means more H3O+ than HO-, means acidic.
High ph ( higher than 7 ) means less H3O+, more OH-, means more basic, less acidic.