Question

What is the pH at the equivalence point of the titration of a strong acid with a strong base?

Answer 1

Strong acids and bases ionizes completely in aqueous medium.

In the titration of strong acid and strong base at equivalence point exactly equal numbers of H⁺ and OH^- ions are ionized and they combine to form H₂O molecules and no H⁺ or OH^- ions present in the solution and hence the solution neither acid nor basic i.e. neutral i.e.pH = 7.

Hence at equivalence point pH of the titration of strong acid with strong base is 7.

[Note : Befor equivalence H+ ion concentration is more than of OH- ion and solution will be acidic with pH<7.

And after equivalence OH- ion concentration is more than of H+ ions and soltion thus basic with pH>7.]

For example titration of HCl (strong acid) and NaOH (strong base)

We have, HCl(aq.) ---------------> Cl^- (aq.) + H⁺(aq.)

NaOH(aq.) ----------------> Na⁺(aq.)+ OH^-(aq.)

At equivalence point, HCl(aq.) + NaOH (aq.) ------------------> Na⁺Cl^- + H₂O.

We can see neither H+ nor OH- present in solution hence the solution is neutral with pH = 7.