Answer:
Formic acid titrated with ammonia (NH3) as a titrant
Explanation:
We have to look at something very critical here and that is, considering whether the acid/ base is strong or weak.
For a weak acid weak base titration, there is no suitable indicator neither is there any sharp pH range because no sharp change occurs. So, for a weak acid-weak base titration, there is only a very small change in pH at the equivalence point. This makes it impractical to carry out a weak acid- weak base titration.
Formic acid is a weak acid and ammonia is a weak base. Hence, Formic acid titrated with ammonia (NH3) as a titrant is a bad titration