Chemistry
posted by Justin on .
What is initial concentration of a sodium acetate if the pH (at epuilibrium) is measured to be 9.30?

............Ac^ + HOH ==> HAc + OH^
initial.....y........0.......0.....0
change.....x...............x......x
equil......yx...............x......x
y = initial concn Ac^ which is our unknown.
pH = 9.30; convert to H^+ which is 5.01E10
Therefore OH^ = Kw/(H^+) = 1E14/5E10 = 2E5 but you should be more accurate.
Kb for acetate = (Kw/Ka for acetic acid) = (HAc)(OH^)/(Ac^)
(Kw/Ka) = (x)(x)/(yx)
For x you insert 2E5; solve for y.