At  250C, the dissociation constant of a base BOH is 1.0 × 10-12. The concentration of hydroxyl ions in 0.01 x M aqueous solution of the base would be

BOH  ⇌   B++OH-So, the dissociation constant of BOH baseKb = B+ OH-BOH          At   equilibrium    B+  =  OH- ∴   Kb=OH-2BOH Given that Kb = 1.0 ×  10-12  and   BOH = 0.01 M Thus,    1.0 ×  10-12 = OH-20.01 OH-2 = 1×10-14 OH- = 1.0×10-7 molL-1