These are questions that go with a \"UV Spectroscopy determination of caffeine u

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These are questions that go with a "UV Spectroscopy determination of caffeine using standard addition." Caffeine and HCl are being mixed. Please help, thank you

1. Calculate* the mass or volume you will need to prepare the following solutions 0.010 M HC 200 ppm caffeine stock solution Prepare 100 mL of this solution by dissolving 20 ppm caffeine standard solution Prepare 50 mL of this solution by diluting l Prepare 1.00 L of this solution by diluting mL of 12.0 M HC gof caffein mL of the 200 ppm caffeine stock solution in 0.010 M HCI Soft drink solution Warm about 80 mL of soft drink solution on a hot plate to expel CO2 (do not boil), then filter the warm liquid through filter paper to remove particulates and allow it to cool to room temperature. 2, Calculate* the volumes required to prepare a set of caffeine test solutions (#1-6) each containing 5 mL of soft drink, and either 0, 0.4,0.8, 1.2, 1.6, or 2.0 ppm of caffeine when diluted to 50 mL with 0.010 M HCl (this will require 6 50-mL volumetric flasks). mL of caffeine standard solution will make 0.4 ppm caffeine ppm caffeine ppm caffeine mL of caffeine standard solution will make 1.6 ppm caffeine mL of caffeine standard solution will make 2.0 ppm caffeine mL of caffeine standard solution will make 0.8 mL of caffeine standard solution will make 1.2

Explanation / Answer

Ans. #1a. Using C1V1 (stock HCl) = C2V2 (diluted HCl)

            Or, (12.0 M x V1) = 0.010 M x 1000.0 mL

            Or, V1 = (0.010 M x 1000.0 mL) / 12.0 M = 0.833 mL

Hence, required volume of 12.0 M HCl = 0.833 mL

#1b. To prepare 100.0 mL of 200 ppm caffeine

Now,

            200 ppm = 200 mg caffeine per liter of solution

                             = 200.0 mg caffeine / 1000.0 mL solution

                             = 20.0 mg caffeine / 100.0 mL solution

                             = 0.020 g caffeine/ 100.0 mL solution.

Preparation: Transfer 0.020 g caffeine in a 100-mL standard volumetric flask. Make the final volume upto the mark with 0.10.M HCl, Mix well for uniform concertation.

It is the desired 200 ppm stock solution of caffeine.

#1c. Using C1V1 (stock caffeine) = C2V2 (diluted caffeine)

            Or, (200 ppm x V1) = 20 ppm x 50.0 mL

            Or, V1 = (20 ppm x 50.0 mL) / 200 ppm = 5.0 mL

Hence, required volume of 200 ppm stock caffeine = 5.0 mL

#2. Given, Final volume to be made upto in all aliquots = 50.0 mL

#2a. Preparation of 0.4 ppm caffeine aliquot:    

Using C1V1 (standard caffeine) = C2V2 (diluted caffeine aliquot)

            Or, (20 ppm x V1) = 0.40 ppm x 50.0 mL

            Or, V1 = (0.40 ppm x 50.0 mL) / 20 ppm = 1.0 mL

Hence, required volume of 20 ppm standard caffeine solution = 1.0 mL

#2b. Calculate all other volumes as #2a.

            V1 = (0.80 ppm x 50.0 mL) / 20 ppm = 2.0 mL

#2c. Calculate all other volumes as #2a.

            V1 = (1.20 ppm x 50.0 mL) / 20 ppm = 3.0 mL

#2d. Calculate all other volumes as #2a.

            V1 = (1.60 ppm x 50.0 mL) / 20 ppm = 4.0 mL

#2e. Calculate all other volumes as #2a.

            V1 = (2.0 ppm x 50.0 mL) / 20 ppm = 5.0 mL

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