The pH of a 1.00 10-3 M solution of pyrrolidine is 10.82. Calculate Kb.

Question

i keep getting anumber that is ^ (positive)

and that's way to big....

Answer 1

pH = 10.82
pOH = 3.18
(OH^-) = 6.61 x 10^-4
If we let pyrollidine be B, then
B + HOH ==> BH+ + OH^-

Then Kb = (BH^+)(OH^-)/(B-OH^-)
My guess is that you haven't used the denominator this way but with (B) = 0.001 AND Kb is small, too, that is necessary.
If you plug in 6.61 x 10^-4 for (BH^+) and for (OH^-) and for the denominator you plug in 0.001-0.000661 or 3.39 x 10^-4, I believe it will work. Check my work carefully. I get something like 0.0013 or close to that for Kb. Again, check my work.