#K_(sp)# values are another set of equilibrium constants....specifically, in the given context, they refer to the following equilibrium...
#Ba(OH)_2(s) rightleftharpoonsBa^(2+) + 2HO^-#
Where...#K_(sp)=[Ba^(2+)][HO^-]^2#..
But we have been given #pH# for a saturated solution... And since #pH# is ALSO another equilibrium measurement, we can address #[HO^-]#...
If #pH+pOH=14#..then here #pOH=2#...and #[HO^-]=10^-2*mol*L^-1#. And so we can fill in the numbers for the solubility expression...
#K_(sp)=underbrace((1xx10^-2)/2)_("concentration of barium ion")xx(2xx10^-2)^2=2.0xx10^-6#
Please review the 'rithmetic, I have already made one mistake...
