Referring to Table 17.3, specify which indicator or...

Referring to Table $17.3,$ specify which indicator or indicators you would use for the following titrations: (a) HCOOH versus NaOH, (b) HCl versus KOH, (c) HNO $_{3}$ versus $\mathrm{CH}_{3} \mathrm{NH}_{2}.$

Key Concepts

Acid-Base Titration

Acid-base titration is an analytical technique used to determine the concentration of an acid or a base in a solution by gradually adding a titrant of known concentration. The process is monitored by the change in pH, which signals when the reacting species have exactly neutralized each other.

Equivalence Point

The equivalence point is the stage in a titration at which the amount of titrant added is chemically equivalent to the amount of substance present in the sample. Its pH depends on the strength of the acids and bases involved; for instance, titrations involving weak acids or bases will have equivalence points that are not neutral.

pH Indicator

A pH indicator is a substance that exhibits different colors at different pH levels and is used to visually signal the occurrence of the equivalence point in a titration. The selection of an appropriate indicator relies on matching its pH transition range with the rapid pH change at the equivalence point.

Weak Acid-Strong Base Titration

In titrations where a weak acid is titrated with a strong base, the equivalence point is typically above 7 due to the formation of a weakly basic conjugate base. This requires the use of an indicator that changes color in the alkaline range to accurately detect the endpoint.

Strong Acid-Strong Base Titration

When a strong acid is titrated with a strong base, the equivalence point is usually around pH 7 because both the acid and base completely dissociate. An indicator with a transition range near neutral pH is optimal for identifying the endpoint in this type of titration.

Strong Acid-Weak Base Titration

For titrations involving a strong acid and a weak base, the equivalence point tends to fall in the acidic range since the conjugate acid formed is relatively strong. Therefore, an indicator that operates within an acidic pH range is ideal to ensure accurate determination of the titration endpoint.

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