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Questions for Ediz to bring the grade for the written quiz to 60%

1. NaF, sodium fluoride, is present in mouthwash. The concentration of fluoride in the mouthwash (so fluoride only!, not sodium) is 220 ppm. If you rinse your mouth with 25 mL of Mouthwash, how many moles of NaF did you use? (Mwt NaF = 42, Awt F = 19)

1. A copper coin of 5 grams was dissolved in 150 mL acid. The copper-acid solution was further diluted to 500 mL. When a subsample was analyzed on FAAS it was out of the calibration range. Therefore, a subsample was diluted 10 times and then the absorbance of 0.365 fit the calibration line: y = 0.346x + 0.001 in a plot of absorbance versus ppm copper. How much copper (%) was present in the coin?

1. A liter of an acidic solution has a pH of 4. It was prepared with 18.2M concentrated H2SO4. How much of the concentrated acid (mL) was used to prepare the acidic solution? Note: assume the acid completely dissociates in protons and sulfate.

1. A titration was performed where Vit C was determined in orange juice. For every three moles of Vitamin C one mole of the titrant KIO3 (potassium iodate) is used (so ratio 3:1). A sample of 20 mL of orange juice was titrated to the end-point with 50 mL of 0.4M KIO3. How many moles of Vit C were present in the 20 mL orange juice sample? How many milligrams of Vitamin C are present in 100 mL of orange juice? (Mwt Vit C = 176.12 g/mol).