Kb =8.0 x 10^-7
Ph =10.00
POH =14-10.00=4
(OH-) = 10^POh
(OH-) is therefore=10^-4=1 x10^-4
let the base be represented by letter B
therefore the equation for reaction is therefore=
B + H2O ----->HB+ + OH-
Kb=( HB+) (OH)/b
8.0 x 10^-7 = { ( 1 x10^-4)(1 x10^-4)}/ b
8.0 x10^-7= 1 x10^-8 /b
multiply both side by b
=8.0 x 10^-7b =1 x 10^-8
divide both side by 8.0 x 10^7
concentration of b is therefore=0.01225M