Over time, as their free fatty acid (FFA) content increases,edible fats and oils become rancid. To measure rancidity, the fator oil is dissolved in ethanol, and any FFA present is titrated withKOH dissolved in ethanol. In a series of tests on olive oil, a stocksolution of 0.050 Methanolic KOH was prepared at 25C, storedat 0C, and then placed in a 100-mL buret to titrate any oleic acid[CH₃(CH₂)₇CH=CH(CH₂)₇COOH] present in the oil. Each offour 10.00-g samples of oil took several minutes to titrate: thefirst required 19.60 mL, the second 19.80 mL, and the third and fourth 20.00 mL of the ethanolic KOH.(a) What is the apparent acidity of each sample, in terms of mass% of oleic acid? (Note:As the ethanolic KOH warms in the bu-ret, its volume increases by a factor of 0.00104/C.)(b) Is the variation in acidity a random or systematic error? Ex-plain.(c) What is the actual acidity? How would you demonstrate this?
Over time, as their free fatty acid (FFA) content increases,edible fats and oils become rancid. To measure rancidity, the fator oil is dissolved in ethanol, and any FFA present is titrated withKOH dissolved in ethanol. In a series of tests on olive oil, a stocksolution of 0.050 Methanolic KOH was prepared at 25C, storedat 0C, and then placed in a 100-mL buret to titrate any oleic acid[CH₃(CH₂)₇CH=CH(CH₂)₇COOH] present in the oil. Each offour 10.00-g samples of oil took several minutes to titrate: thefirst required 19.60 mL, the second 19.80 mL, and the third and fourth 20.00 mL of the ethanolic KOH.(a) What is the apparent acidity of each sample, in terms of mass% of oleic acid? (Note:As the ethanolic KOH warms in the bu-ret, its volume increases by a factor of 0.00104/C.)(b) Is the variation in acidity a random or systematic error? Ex-plain.(c) What is the actual acidity? How would you demonstrate this?
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