Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): Phenolphthalein is not a suitable indicator for the titration of aqueous ammonia against hydrochloric acid. Reason (R): The pH at the equivalence point of this titration is less than 7, and the sharp change in pH does not overlap with the working range of phenolphthalein. In the light of the above

Step-by-step solution

Aqueous ammonia ( NH₄OH ) is a weak base and hydrochloric acid ( HCl ) is a strong acid. Their titration results in the formation of the salt NH₄Cl , which undergoes cationic hydrolysis, making the solution acidic at the equivalence point (pH The sharp change in pH near the equivalence point for a strong acid-weak base titration occurs roughly between pH 7 and 3. Phenolphthalein has a working pH range of 8.0 to 9.8, which does not overlap with this sharp change. Therefore, phenolphthalein fails to indicate the end