EDTA: Dry Na2H2EDTA • 2H2O (FW 372.25) at 80 oC for 1 h and coolin the desiccator. Accurately weigh out 0.6045g and dissolve itwith heating in 400 ml of DI in a 500-ml volumetric flask. Cool toroom temperature, dilute to the mark, and mix well.
Pipet a 25.00 ml sample of the unknown into a 250-ml flask.Dilute with an additional 25 ml of DI H2O (you can use a graduatedcylinder for the water addition, it is added to help clarify thecolor change). To each sample add 3 ml of pH 10 buffer and a 2drops of Eriochrome black T indicator. Titrate with EDTA from your50-ml buret and note when the color changes from wine red toblue.
Volume | sample [1] | sample [2] | sample [3] |
initial | 1.290 mL | 2.400 mL | 3.150 mL |
final | 12.810 mL | 13.850 mL | 14.420 mL |
total | 11.520 mL | 11.450 mL | 11.270 mL |
Using these results,
[1] calculate the molarity of EDTA.
[2] calculate [Ca2+] ion and [Mg2+] ion for each?
[3] calculate the average concentration of Ca2+ and Mg2+ foreach.
[4] calculate the water hardness in terms of CaCO3
Please show work!
