Question

The pH change around the equivalence point for strong-base/weak-acid titration is usually not as great as that for strong-base/strong-acid. The statement is true or not. Explain.

Answer 1

The equivalence point is at which the tritrant added is just enough to neutralize a analyse solution.

During the strong acid and strong base tration at equivalence point pH will be neutral and upon excess base the pH increases very rapidly.

Similarly for a strong base and weak acid

Which means if the titrant is weak acid then the fall in pH upto equivalence point is fast but when at equivalence point the further fall in pH is very slow.

but if the titrant is base and analyte is weak acid the raise in pH is intially fast and slow nearing the equivalence point . However after the equivalence point the raise pH is very rapid similar to strong acid and strong base titration.

The point to be understood that the conjugate base of weak acid is a strong base.

Which if consider CH3COOH as weak acid then the conjugate base is CH3COO- is strong base

Hence at equivalence point the solution will be slightly basic.

Therefore the above statement is false. As at equivalence point if titant is strong base then the raise pH is very fast if it is vice versa that means the titrant is weak acid then fall in pH is very slow