What would the titration of a polyprotic acid with a strong base look like?
The titration of a polyprotic acid with a strong base would involve the neutralization of each acidic proton one by one.
For example, let's consider the titration of phosphoric acid (H3PO4) with sodium hydroxide (NaOH). Phosphoric acid is a triprotic acid, meaning it can donate three protons (H+ ions).
Initially, as the strong base is added to the acid, the first proton will be neutralized. The pH of the solution increases gradually as the base reacts with the acid. At this point, we have partially neutralized phosphoric acid, resulting in the formation of dihydrogen phosphate (H2PO4-) ions.
The reaction would be:
H3PO4 + NaOH -> H2PO4- + Na+ + H2O
As more sodium hydroxide is added, the second acidic proton of dihydrogen phosphate is neutralized, forming hydrogen phosphate (HPO42-) ions.
The reaction would be:
H2PO4- + NaOH -> HPO42- + Na+ + H2O
Finally, with the addition of more sodium hydroxide, the last acidic proton of hydrogen phosphate is neutralized, forming phosphate (PO43-) ions.
The reaction would be:
HPO42- + NaOH -> PO43- + Na+ + H2O
During the titration, the pH of the solution would gradually increase as each acidic proton is neutralized. The pH curve would show a characteristic "step-wise" shape, with distinct pH jumps corresponding to the neutralization of each proton.