Part 1: Precipitation of Sulfate
Obtain an unknown water sample from the prep-room and be sure to record the unknown number in the lab notebook. Obtain four glass bottles and clean them thoroughly. Pipet 50 mL of the unknown water sample from the bottle using a 25 mL volumetric pipet into each of the four bottles. To each of these bottles, add 10 drops of concentrated HCl (be sure to do this under the hood). Pipet 10 mL of BaCl2 into each of the bottles using a 10 mL volumetric pipet. Wash a stir bar and add one to each bottle. In order to prevent any evaporation of the liquid, aluminum foil should be placed over each bottle. Place the bottles on a hotplate and heat to boiling for one hour. Be sure to rotate the bottles to ensure even heating.
Part 2: Preparation and Standardization of the EDTA Solution
Clean a 600 mL beaker and add 500 mL of nanopure water. Clean another stir bar, add it to the beaker and begin to stir. Weigh out approximately 0.925 g of Na2C10H14N2O8 x 2 H2O. This does not need to be weighed out by difference. Add this slowly to the stirring 500 mL of water. Allow up to 20 minutes for complete dissolution. In the meantime, the roughly 0.005 M ZnSO4 solution will need to be made. This is done by pipeting 25 mL of standardized zinc sulfate into a 250 mL volumetric flask and diluting to the mark. The buret should be filled with this solution, but be sure to rinse it through first. Once the EDTA has completely dissolved, transfer it to a 1L bottle. Shake it for several minutes to ensure that everything is dissolved and properly mixed. Pipet 15 mL of this solution into four Erlenmeyer flasks and add an additional 5 mL of pH 10 buffer solution to each flask. Prepare the Eriochrome Black T indicator by dissolving a spatula tip amount in roughly 20 mL of nanopure water. Add 13-15 drops of this indicator into each flask right before titrating. The solution will turn a pale blue. Titrate all four samples until the pink endpoint has been met....