Calculate the molarity of the EDTA:

	blank	Ca sample	tap water
final vol (mL)	8.62	28.5	48.6
initial vol (mL)	3.40	8.64	28.5
volume used	5.22	19.9	20.1

A blank is run where 15 drops of 0.03 M MgCl2 is titrated with EDTA using Erichrome Black T indicator in a buffer 10 solution.

Next a Calcium sample is titrated where 0.21 g of CaCO3 is dissolved in HCl and then excess HCl removed through boiling and then diluted to 500 mL with distilled water. The 15 drops of MgCl2 are used as well in this titration. 10 mL of the standard Ca solution is used.

Last tap water is titrated where 15 drops of 0.03 M MgCl2 and 22.0 mL of tap water.

Calculate the molarity of the EDTA