Explain with suitable examples and equation the titration of polyprotic acid versus strong base.
Let’s assume our analyte is acetic acid 
(weak acid) and the titrant is sodium hydroxide NaOH (strong base). If we start plotting the pH of the analyte against the volume of NaOH that we are adding from the burette, we will get a titration curve as shown below.
As NaOH is added dropwise,
slowly starts getting consumed by 
(produced by dissociation of 
But analyte is still acidic due to predominance of 
ions.
Point 2: This is the pH recorded at a time point just before complete neutralization takes place.
Point 3: This is the equivalence point (halfway up the steep curve). At this point, moles of 
added = moles of 
in the analyte. The 
ions are completely neutralized by 
ions. The solution contains only 
salt and 
Let me pause here for a second - can you spot a difference here as compared to case 1 (strong acid versus strong base titration)??? In the case of a weak acid versus a strong base, the pH is not neutral at the equivalence point. The solution is basic (pH ~ 9) at the equivalence point. Let’s reason this out.
As you can see from the above equation, at the equivalence point the solution contains 
salt. This dissociates into acetate ions 
and sodium ions 
As you will recall from the discussion of strong/ weak acids in the beginning of this tutorial, 
is the conjugate base of the weak acid 
is relatively a strong base (weak acid 
has a strong conjugate base), and will thus react with 
to
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