Asked by Amber

Write a balanced equation for the proton transfer reaction between water and phosphate ion. Determine in which direction the equilibrium is favored.
Answered by DrBob222
HOH + PO4^3- ==> HPO4^2- + OH^-
Products are favored. Do you know why?
Answered by Amber
I want to say because it has more of the reactant. Am I right?
Answered by DrBob222
I think I want to change my answer. I believe the reactants are favored.

Calculate the Kb for the base.
PO4^3- + HOH ==> HPO4^2- + OH^-
Kb for PO4^3- = (Kw/k3 for H3PO4) = 1E-14/4.2E-13 = about 0.024. Even though 0.024 is a "relatively" large number in Kb terms (and PO4^3- is a strong base in terms of pH), it is less than 1 which means the numerator is small and the denominator is large. That means that the reactants predominate at equilibrium.
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