[zeshkani]

hi there

i got a question on how to calculate the Kf value of this equation, the question asks "what is the formation constant for teh reaction between Mg and EDTA ?

Mg(+2) + EDTA(-4) <---> Mg . EDTA(-2)

i have the concentrations on the following

Mg(+2) = 2.20 (+-.03) x10 ^-6
[Mg . EDTA(-2)] = 2.97(+-.05) x 10^-3
EDTA(-4) = 2.22(+-.05) x10^-6

any help is welcome
thanks alot

[Albert]

Check this out: http://www.rit.edu/~uphysics/uncertainties/Uncertaintiespart2.html#muldiv

[kemometrik]

Kf = [MgEDTA]/[M].[EDTA]

so for propagation error, first you calculate  uncertainity for denominator sd/Rd = square root ((unc Mg/Conc Mg)^2 + (unc. EDTA/Conc EDTA)), Rd = [M].[EDTA], then the result for denominator is Rd+-Sd.

Next, Kf is calculated from [MgEDTA]/Rd, the uncertainity calculated by su/Kf= square root ((sd/Rd)^2 + (unc. MgEDTA/Conc MgEDTA))

And the final result is Kf+-su

Hope this help (ref. Modern Analytical Chemisty by David Harvey)

Thanks

Kemometrik

[zeshkani]

thanks that helped alot