EDTA Dry Na2H2EDTA 2H2O (FW 372 25) at 80 oC for 1 h and coolin the ...

EDTA: Dry Na2H2EDTA â€¢ 2H2O (FW 372.25) at 80 oC for 1 h and cool in...

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Chemistry

EDTA: Dry Na2H2EDTA â€¢ 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!

Answer & Explanation Solved by verified expert

3.7 Ratings (489 Votes)

1 Drying process will remove two water molecules from each EDTA2H2O molecule So molecular weight of dry EDTA 3722536 33625 Molarity of EDTA weight in g molecular weight volume in liters 0604533625 05 000359 M 2 The See Answer

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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