irst time we did a titration with a known concentration of Ca ions. The next time we did the titrations we used our water sample which gave us the calculation of the concentration of the Ca ions in our sample. This is what we used to compare the hardness of our sample.This titration test procedure consisted of adding a drop of EBT indicator and a drop of NH3/NH4Cl/MgEDTA buffer to a drop of the water sample. The hard water sample is then titrated with the EDTA. This experiment determines the hardness by first forming a basic solution with the buffer and having the indicator show this. Then, when the EDTA is added, it first reacts with the Ca and forms a colorless chelate, and then the Mg reacts with it forming another colorless chelate. After all of the Mg has reacted with the EDTA, the titration is complete and the indicator shows the solution as a clear blue. The amount of ions in the solution can be determined by setting up a ratio between the drops (volumes) of EDTA and the ions and equating it to the ratio of the concentrations of the two. This is the formula you should use in order to find the unknown titration:CEDTA VEDTA = CIONS VIONS-Example of calculation 1 -(2.00 x 10-4 M) x 14 drops = CIONS x 1 drop CIONS = .0028 MSince the concentration of the ions is known in Molars, it can be converted to parts CaCO3 per million, the standard hardness unit. The following example is a guidline of how to convert the units. Example of calculation 2- 3.2 x10-3 mol CaCO3 x100 g CaCO3x1000 mg CaCO3=320 mg =320 mg=320 ppm liter mol CaCO3 1 g CaCO3 L 1000 gThe last part of the experiment was to do a EDTA titration with our water sample and an added comerical agent water softener. This part of the procedure was to show the effect that water softeners have on the ions in the water. The first softener used was baking soda and the second softener was done by resin beads ...
