# What sort of acid is phosphoric acid in aqueous solution?

Because the parent acid is potentially triprotic.............and phosphate salts, i.e. salts of $P {O}_{4}^{3 -}$ are possible.
I write $\text{potentially}$ because in aqueous solution, phosphoric acid is to all intents and purposes, a diacid:
${H}_{3} P {O}_{4} \left(a q\right) + 2 K O H \left(a q\right) \rightarrow {K}_{2} H P {O}_{4} \left(a q\right) + 2 {H}_{2} O \left(l\right)$,
i.e. the salt is potassium biphosphate, ${K}_{2}^{+} {\left[H P {O}_{4}\right]}^{2 -}$