pH = -log[H+] = 7
[H+] = 1 x 10^-7 M
pKa = -log[Ka]
So for EDTA,
Ka1 = 6.92 x 10^-3 ; Ka2 = 7.58 x 10^-4 ; Ka3 = 5.37 x 10^-7 ; Ka4 = 1.12 x 10^-11
[A] = [H+]^4 + Ka1[H+]^3 + Ka1Ka2[H+]^2 + Ka1Ka2Ka3[H+] + Ka1Ka2Ka3Ka4
= 1 x 10^-28 + 6.92 x 10^-24 + 5.24 x 10^-20 + 2.81 x 10^-19 + 3.15 x 10^-23
= 3.33 x 10^-19
alpha0 = [H+]^4/[A] = 1 x 10^-28/3.33 x 10^-19 = 3.00 x 10^-10
alpha1 = Ka1[H+]^3/[A] = 6.92 x 10^-24/3.33 x 10^-19 = 2.08 x 10^-5
alpha2 = Ka1Ka2[H+]^2/[A] = 5.24 x 10^-20/3.33 x 10^-19 = 0.157
alpha3 = Ka1Ka2Ka3[H+]/[A] = 2.81 x 10^-19/3.33 x 10^-19 = 0.844
alpha4 = Ka1Ka2Ka3Ka4/[A] = 3.15 x 10^-23/3.33 x 10^-19 = 9.46 x 10^-5
EDTA (ethylenediaminetetraacetic acid), a widely used complexing agent, is a tetraprotic acid with the following pK_a...
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Ethylenediaminetetraacetic acid (EDTA) is used for a range of applications because of its ability to strongly bind metal ions via its six ligating groups. EDTA is used in the paper industry to bind Mn2+ (and other metal) ions from catalyzing the decomposition of hydrogen peroxide (H2O2), which is an important chemical for bleaching the pulp. In this example, we are going to focus on the chelation of free Mn2+ ions in a solution at pH = 7. (a) If there...
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