Determining hardness of water using EDTA ?

hello,

I got a sample of water I didn’t measure how much I put into my volumetric flask perhaps it was 8.5ml but I don’t think I need it, but I do use it which made me believe I was wrong.

The sample was made up to 100ml 10ml of this dilution was used as the anaylte along with buffer and the indicator

I Titrated 9.07ml of EDTA with a concentration of 0.0185moldm3

So the calculation i did was

Moles of edta= (9.07x0.0185)/1000= 0.000167795 Moles of Ca2+ is the same So then I find the mass of Ca = 40x0.000167795= 0.0067188g



Please help.
Thanks!

I didn't find the right solution from the Internet.


References:
www.chemicalforums.com/index.php?topic=93004.0


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