Use Table 6H.2 to suggest suitable indicators for the titrations described in Exercises 6H.9 and 6H.14.

Exercises 6H.9

Benzoic acid, C₆H₅COOH, is used as a preservative in food and cosmetics because it is considered to be relatively safe.

Suppose you are studying benzoic acid and need to predict the pH of a benzoic acid solution during a titration. Calculate the pH at the stoichiometric point of the titration of 25.00 mL of 0.120 m C₆H₅COOH(aq) with 0.0230 m NaOH(aq).

Exercises 6H.14

Suppose that 30.0 mL of 0.12 m C₆H₅COOH(aq) is titrated with 0.20 m KOH(aq).

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TABLE 6H.2 Indicator Color Changes* pH range of color change Indicator thymol blue methyl orange bromophenol blue bromocresol green methyl red litmus bromothymol blue phenol red thymol blue phenolphthalein alizarin yellow R alizarin pKin 1.7 3.4 3.9 4.7 5.0 6.5 7.1 7.9 8.9 9.4 11.2 11.7 1.2 to 2.8 3.2 to 4.4 3.0 to 4.6 3.8 to 5.4 4.8 to 6.0 5.0 to 8.0 6.0 to 7.6 6.6 to 8.0 8.0 to 9.6 8.2 to 10.0 10.1 to 12.0 11.0 to 12.4 Color of acid form red red yellow yellow red red yellow yellow yellow colorless yellow red Color of base form yellow yellow blue blue yellow blue blue red blue pink red purple