Homework 3 pharmaceutical measurement density key.pdf - Homework 3 – Pharmaceutical measurement and density KEY[Please do not forget to add units

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1 Homework 3 – Pharmaceutical measurement and density - KEY [Please do not forget to add units, including the % symbol when asked about percentage of error] 1. How would a pharmacist measure 60 mg of propylparabene using ethanol as a diluent, if the minimum weighable quantity for the balance is 110 mg? A. Dissolve 60 mg propylparabene in 10 mL ethanol and take 2 mL from the solution, which will contain 60 mg propylparabene. B. Dissolve 90 mg propylparabene in 12 mL ethanol and take 9 mL from the solution, which will contain 60 mg propylparabene. C. Dissolve 120 mg propylparabene in 5 mL ethanol and take 6 mL from the solution which will contain 60 mg propylparabene. D. Dissolve 0.3 g propylparabene in 50 mL ethanol and take 10 mL from the solution, which will contain 60 mg propylparabene. Answer is D. Option A and B can be eliminated instantly because we cannot weigh 60 and 90 mg in a balance that has a MWQ of 110 mg. Then, calculate the remaining options as below by ratio-proportion method (in whatever arrangement you feel more comfortable) to find the correct answer. The instructions in option D yields 60 mg, which is what the pharmacist is supposed to weigh. So D is the correct answer. Drug for Rx = Total drug weighed Drug-diluent for Rx (Aliquot) Total drug-diluent c. X mg = 120 mg X = 144 mg 6 mL 5 mL d. X mg = 300 mg X = 60 mg 10 mL 50 mL 2. Using the aliquot method, how would a pharmacist measure 30 mg of atropine sulfate if the minimum weighable quantity for the balance he or she is using is 50 mg and the diluent is lactose?
2 A. Weigh 60 mg atropine sulfate and dilute to 200 mg with lactose. From this mixture, remove 120 mg that will contain the necessary 30 mg atropine sulfate. B. Weigh 80 mg of atropine sulfate and dilute to 240 mg with lactose. From this mixture, remove 90 mg that will contain the necessary 30 mg atropine sulfate. C. Weigh 40 mg atropine sulfate and dilute to 250 mg with lactose. From this dilution, remove 50 mg that will contain the necessary 30 mg atropine sulfate. D. Both b and c are correct.

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