Question

Molybdenum (Mo) is a heavy metal that can have severe health effects on humans and animals. Tailings from a mining operation in Colorado have polluted surface waters used by grazing animals with Mo. Based on the following information determine the concentration of the three Mo species in the stream. [Mo]T = 5.1x10^-4 M pH = 4.20

H2MoO4 (aq) = HMoO4^1- (aq) + H+ (aq) pKa1 = 4.0

HMoO4^1- (aq) = MoO4^2- (aq) + H+ (aq) pKa2=4.24

Answer 1

Are you in to mole fractons or alpha zero, alpha 1 and alpha 2?

Answer 2

Mole fractions

Answer 3

X(H2MoO4) = (H^+)^2/D
X(HMoO4^-) = k1(H^+)/D
X(MoO4^2-) = k1k2/D
where D is denominator and that =
(H^+)^2 + k1(H^+) + k1k2

when you finish calculating each mole fraction, then X*5.1E-4 = (that specie)

There is another way to do this without mole fractions. It's about as long to do it that way but it has the advantage of not using those formula I have above. If you've seen those derived you know where they come from.