0.25 mL of lemon juice is probably too much already.
She’s doing the maths for the concentration of citric acid in lemon juice through the formula C(acid) = 10^(-pH). That works fine for a strong acid, because you can be pretty sure all that acid in the solution is dissociated, and thus lowering its pH… but citric acid is weak - and weak acids don’t dissociate properly in already acidic conditions.
This means there’s probably way more acid in that solution than the pH makes you believe, but that acid will react once you raise the pH, by mixing the lemon juice into the water.
(I don’t blame her for using the strong acid maths. It’s already enough to convey her point, plus the maths for weak acids is a bloody pain.)
0.25 mL of lemon juice is probably too much already.
She’s doing the maths for the concentration of citric acid in lemon juice through the formula C(acid) = 10^(-pH). That works fine for a strong acid, because you can be pretty sure all that acid in the solution is dissociated, and thus lowering its pH… but citric acid is weak - and weak acids don’t dissociate properly in already acidic conditions.
This means there’s probably way more acid in that solution than the pH makes you believe, but that acid will react once you raise the pH, by mixing the lemon juice into the water.
(I don’t blame her for using the strong acid maths. It’s already enough to convey her point, plus the maths for weak acids is a bloody pain.)