In: Chemistry
What is the pH at the equivalence point of the titration of a strong acid with a strong base?
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.