Given the acid-base indicators in Question 37, select a...

Given the acid-base indicators in Question $37,$ select a suitable indicator for the following titrations. (a) sodium formate $\left(\mathrm{NaCHO}_{2}\right)$ with $\mathrm{HNO}_{3}$ (b) hypochlorous acid with barium hydroxide (c) nitric acid with $\mathrm{HI}$ (d) hydrochloric acid with ammonia

Given the acid-base indicators in Question $37,$ select a suitable indicator for the following titrations.
(a) sodium formate $\left(\mathrm{NaCHO}_{2}\right)$ with $\mathrm{HNO}_{3}$
(b) hypochlorous acid with barium hydroxide
(c) nitric acid with $\mathrm{HI}$
(d) hydrochloric acid with ammonia

Key Concepts

Acid?Base Titration

Acid–base titrations are analytical procedures used to determine the concentration of an acid or base by reacting it with a titrant of known concentration. The reaction typically proceeds until the equivalence point is reached, where stoichiometrically equivalent amounts of acid and base have been mixed. Understanding the nature of the acid and base involved (strong vs weak) is vital for predicting the pH changes during the titration.

Equivalence Point

The equivalence point in a titration is the stage at which the amount of titrant added exactly neutralizes the analyte. Its pH value depends on the strengths of the reacting acid and base. For example, titrations involving a weak acid and a strong base or vice versa will have an equivalence point that deviates from neutral pH, influencing the choice of indicator.

Acid–Base Indicators

Acid–base indicators are substances that change color at a particular pH range. They are essential in titrations to signal the endpoint of the reaction. An ideal indicator has a transition range that straddles the pH of the equivalence point, ensuring that the color change coincides with the completion of the neutralization reaction.

Indicator Selection Criteria

Selecting a suitable indicator depends on matching the pH transition range of the indicator with the expected pH at the equivalence point of the titration. This involves analyzing the titration curve and considering the acid-base strengths of the substances involved, ensuring that the indicator’s color change occurs sharply and at the proper stage of the titration.

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