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How do you calculate the concentrations using the absorbance?

How do you calculate the concentrations using the absorbance?

Chemistry
Chemistry
10th Edition
ISBN:9781305957404
Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Publisher:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCoste
Chapter1: Chemical Foundations
Section: Chapter Questions
Problem 1RQ: Define and explain the differences between the following terms. a. law and theory b. theory and...
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How do you calculate the concentrations using the absorbance?

Penicillin G reacts with hydroxylamine (NO20H) according to the following reaction: P + NH20H → NH20HP to form hydroxamic acid, which produces a colored complex with Fe(III). To determine the overall reaction order, equal concentrations of penicillin (P) and hydroxylamine (NO20H) were mixed together in a 250 mL flask [J. Chem. Educ., 49, 539 (1972)]. Samples were withdrawn every 10 minutes and added to a solution containing iron (III) chloride. Absorbance measurements obtained with the aid of a colorimeter were obtained as a function of time. The absorbance shown in the table below is known to be directly proportional to the hydroxamic acid (NH20HP) concentration. Run time, min Absorbance 0 4 5 20 30 40 50 |1000 (or ∞) 0.34 0.43 0.5 0.54 0.56 1 3 7 10 0.69 Hint: Notice you can build a linear calibration between Absorbance (A) and conversion (xa); i.e. Xa, 0 → 1 (t, 0 → ∞) while A, 0 → 0.69 Using both [the value at t → ∞ is provided as a reference for calibration only, not to be used in the kinetic analysis]
Transcribed Image Text:Penicillin G reacts with hydroxylamine (NO20H) according to the following reaction: P + NH20H → NH20HP to form hydroxamic acid, which produces a colored complex with Fe(III). To determine the overall reaction order, equal concentrations of penicillin (P) and hydroxylamine (NO20H) were mixed together in a 250 mL flask [J. Chem. Educ., 49, 539 (1972)]. Samples were withdrawn every 10 minutes and added to a solution containing iron (III) chloride. Absorbance measurements obtained with the aid of a colorimeter were obtained as a function of time. The absorbance shown in the table below is known to be directly proportional to the hydroxamic acid (NH20HP) concentration. Run time, min Absorbance 0 4 5 20 30 40 50 |1000 (or ∞) 0.34 0.43 0.5 0.54 0.56 1 3 7 10 0.69 Hint: Notice you can build a linear calibration between Absorbance (A) and conversion (xa); i.e. Xa, 0 → 1 (t, 0 → ∞) while A, 0 → 0.69 Using both [the value at t → ∞ is provided as a reference for calibration only, not to be used in the kinetic analysis]
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