1. Vodcast Problem Eric Liu June 10, 2007 Chemistry AP

2. The Question: 1987 B Part A Part B Part C This is a “calculations”-type problem. Remember to use your work and answers from earlier parts to help out on later ones! The percentage by weight of nitric acid, HNO 3, in a sample of concentrated nitric acid is to be determined.

3. The Question: Part A Things to keep in mind: monoprotic acid Acid-base neutralization reaction The question! Initially a NaOH solution was standardized by titration with a sample of potassium hydrogen phthalate (also known as KHP), KHC 8 H 4 O 4, a monoprotic acid often used as a primary standard. A sample of pure KHC 8 H 4 O 4 weighing 1.518 grams was dissolved in water and titrated with the NaOH solution. To reach the equivalence point, 26.90 milliliters of base was required. Calculate the molarity of the NaOH solution. (Molecular weight: KHC 8 H 4 O 4 = 204.2)

4. The How-to: Part A Acid-base neutralization reaction 1 to 1 mole ratio

5. The Question, cont.: Part B Things to keep in mind: Info, work, answers from Part A Dilution Work Backwards Titration Units A 10.00 milliliter sample of the concentrated nitric acid was diluted with water to a total volume of 500.00 milliliters. Then 25.00 milliliters of the diluted acid solution was titrated with the standardized NaOH solution prepared in Part A. The equivalence point was reached after 28.35 milliliters of the base had been added. Calculate the molarity of the concentrated nitric acid.

6. From Part A.2764M NaOH 1 to 1 mole ratio.007836molNaOH =.007836molHNO 3 The How-to: Part B The equivalence point was reached after 28.35 milliliters of the base had been added. Then 25.00 milliliters of the diluted acid solution was titrated with the standardized NaOH solution prepared in Part A. A 10.00 milliliter sample of the concentrated nitric acid was diluted with water to a total volume of 500.00 milliliters. Then 25.00 milliliters of the diluted acid solution…

7. The Question, cont.: Part C Things to keep in mind: Info, work, answers from Part B The question! The density of the concentrated nitric acid used in this experiment was determined to be 1.42 grams per milliliter. Determine the percentage by weight of HNO 3 in the original sample of concentrated nitric acid.

8. The How-to: Part C Density: 1.42 g/mL From Part B.1567mol HNO 3 in the 10.00mL sample

9. The Conclusion You’ve just finished 1987 B of an actual Chemistry AP Test! Congrats.