Calculations

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kc85
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Calculations

 Hi Everyone,

I wonder if anybody could offer some help on a basic calculation which is causing us some difficulty. I'm sure it is a simple calculation.

We need to work out what theoretical volume of 0.015M EDTA corresponds to 1mg/L Calcium Carbonate in 100mL of sample. We have come up with the following, could somebody verify this or correct the calculation?

For 100ml of 1mg/L CaCO3 (100.0869)  = 0.00000999mol/L
Mole = (volume x concentration) / 1000
            = 100 x 0.00000999 / 1000
            = 0.000000999 mol
Equivalent EDTA
0.000000999 = v x 0.015 / 1000
                      V = 0.0666ml
                          = 66.6uL

Similarly we need to calculate what volume of 0.035M EDTA corresponds to 20mg/L of calcium carbonate in 5.5ml of sample:
 
For 100ml of 20mg/L CaCO3 = 0.0001998 mol/L
Mole = (volume x concentration)/ 1000
            = 100 x 0.0001998 / 1000
            = 0.00001998
Equivalent EDTA
0.00001998 = v x 0.035 / 1000
                    v = 0.5709ml
                       = 570.9uL
For 5.5ml (tube is approx. 5.5 ml)=31.3995µL
Thanks for any help