Use Table 6H.2 to suggest suitable indicators for the titrations described in Exercises 6H.10 and 6H.12.

Exercises 6H.10

Morphine, C₁₇H₁₉O₃N, is a potent painkiller. Suppose you are studying morphine and need to predict the pH of a morphine solution during a titration. Calculate the pH at the stoichiometric point of the titration of 30.00 mL of 0.0172 m C₁₇H₁₉O₃N(aq) with 0.0160 m HCl(aq).

Exercises 6H.12

Suppose that 0.483 g of an unknown weak acid, HA, is dissolved in water. Titration of the solution with 0.250 m NaOH(aq) required 42.0 mL to reach the stoichiometric point. After the addition of 21.0 mL, the pH of the solution was found to be 3.75.

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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