chemistry
posted by Anonymous on .
A certain weak base has a Kb of 8.40 × 107. What concentration of this base will produce a pH of 10.34?

pH = 10.34
pOH = 1410.34 = 3.66
Then (OH^) = about 2E4 but that's only an estimate.
........BOH ==> B+ + OH^
I........x.......0.....0
C.......y.......y.....y
E.......xy .....y.....y
Kb = 8.4E7 = (B^+)(OH^)/(HB)
You know y and Kb, substitute into Kb expression and solve for x. 
I don't understand what Y and X are supposed to be