Question

For water hardness experiment using EDTA titrant:

1. Suppose water hardness was 600mg CaCO3/L, how much sample should be used to ensure 10-50mL of titrant will be used (assuming titer of 1.00mg CaCO3/ml EDTA)

2. How can EDTA be used to analyze other multivalent cations? If not, why?

Answer 1

You want to use about 40 mL of the titrant which is 1 mg/mL. That means
1 mg/mL x 40 mL = about 40 mg sample.
To get 40 mg of the sample, which is 600 mg/L (600 mg/1000 mL = 0.600 mg/mL) means
0.600 mg/mL x ?mL = 40 mg and solve for mL. I get about 66.7 mL. That isn't conveniently measured so I would take a 50 mL aliquot. Work that through to make sure you use between 10 and 50 mL but I think that will be 30 mL of the titrant. Check that out.

2. Yes, EDTA can be used to analyze other cations so I don't understand the if not, why part.