When titrating a 30ml mixture formed by hypochlorous, benzoic and dichloroacetic acids, with 0.5M potassium hydroxide, the following titration curve was obtained: *Curve was added as picture a) Determine the concentrations of the acids in the initial mixture b) Explain the shape of the curve, using the reaction prediction scale c) Calculate the pH in the initial mixture and at the equivalence points
When titrating a 30ml mixture formed by hypochlorous, benzoic and dichloroacetic acids, with 0.5M potassium hydroxide, the following titration curve was obtained:
*Curve was added as picture
a) Determine the concentrations of the acids in the initial mixture
b) Explain the shape of the curve, using the reaction prediction scale
c) Calculate the pH in the initial mixture and at the equivalence points
d) Estimate the error maximum that would be committed if we used erythrosine disodium as indicator to detect the first equivalence point
e) Estimate the maximum error that would be committed if we used bromocresol purple as indicator to detect the first equivalence point
f) Can phenolphthalein be used to detect the third equivalence point within 3% error?
g) Write the table of the reaction scheme.
h) Write the table of variation of quantities
i) Obtain the expressions of pH = f (V) for each stage of the titration.
j) Calculate the quantivity at each equivalence point.
Data:
Hypochlorous acid: pKA = 7.1
Benzoic acid: pKA = 4.2
Dichloroacetic acid: pKA = 1.3
| Indicator | Turning interval |
| Erythrosine disodium | 2.2 ≤ pH ≤ 3.6 |
| Bromocresol purple | 5.2 ≤ pH ≤ 6.8 |
| Phenolphthalein | 8.0 ≤ pH ≤ 9.6 |
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