1) A 0.1967 g sample of pure ascorbic acid is weighed out and dissolved in 50 mL of distilled water in an Erlenmeyer flask. One week later, when one third of the water in the flask has evaporated, this solution is titrated against 0.01735 M KI03 solution and requires 18.75 mL of it to reach the end point.
a. What mass of ascorbic acid has been oxidized by one of the components of air over the weeklong waiting period?
b. What has happened to the concentration of ascorbic acid in the solution in the flask over this waiting period (before the titration.)? Show your calculations.
2) An old container of KOH has been found in the chemistry lab. A 4.00 g sample of this impure KOH is dissolved in 30.0 mL of 2.500 M HCI, transferred to a 250 0 mL volumetric flask and diluted to the mark with distilled water. A 15.00 mL sample of the resulting solution is pipetted into an Erlenmeyer flask and titrated with 4.32 mL of standardized 0.120 MNaOH. Determine the percent purity of the sample of KOH found in the lab (Molar mass of KOH = 56.1 g/mol).
3) An unknown mass of MgCl2 was dissolved in sufficient water to fill a 250.0 mL volumetric flask to the mark. A 10.00 mL aliquot was taken from the flask and titrated with 3.64 x 10-2MAgNO3 solution resulting in the formation of 82.4 mg of solid AgC1 (Molar mass = 143.3 g/mol). Determine the mass of MgC12 (Molar mass = 95.2 g/mol) that was added to the original 250 0 mL volumetric flask as well as the volume of AgNO3 solution used in the titration.