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Hardness of water determination using a titration Watch

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    I have been asked to work out the hardness of water in German degrees and this is what I did:

    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

    Now my issue

    So 0.0067188g of Ca in the 10ml therefore in the 100ml there will be 10 times that, as it was a dilution. So 0.067188g which is 67.118mg

    So there is 67.118mg of Ca in my 8.5ml sample/ 100ml volumetric flask
    Now a 1 German degree is 10mg of Ca per 1000ml So is there 7896.2mg in 1000ml of sample Therefore having 789.6 German degree of hardness?

    I think this is wrong though
 
 
 
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