Quinine in a 1.664-g antimalarial tablet was dissolved in sufficient 0.10 M HCl to give 500 mL of solution. A 15.00-mL aliquot was then diluted to 100.0 mL with the acid. The fluorescence intensity for the diluted sample at 347.5 nm provided a reading of 288 on an arbitrary scale. A standard 100 ppm quinine solution registered 180 when measured under conditions identical to those for the diluted sample. Calculate the mass of quinine in milligrams in the tablet.

Question

Chemistry

Mike Baxter

29 September, 01:16

Quinine in a 1.664-g antimalarial tablet was dissolved in sufficient 0.10 M HCl to give 500 mL of solution. A 15.00-mL aliquot was then diluted to 100.0 mL with the acid. The fluorescence intensity for the diluted sample at 347.5 nm provided a reading of 288 on an arbitrary scale. A standard 100 ppm quinine solution registered 180 when measured under conditions identical to those for the diluted sample. Calculate the mass of quinine in milligrams in the tablet.

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Braden Holmes · Answer 1

533.33 mg quinine

Explanation:

First we calculate the concentration of the diluted sample, using the values obtained by the standard:

288 * 100 ppm / 180 = 160 ppm

Now we use the dilution factors to calculate the concentration of quinine in the original sample:

160 ppm * 100mL/15mL = 1066.67 ppm

ppm can be defined as mg of quinine/L solvent:

500 mL solution ⇒ 500/1000 = 0.5 L

1066.67 ppm * 0.5L = 533.33 mg quinine