CO3^2- + H2O <---> H2CO3 + OH-
the equilibrium constant expression for this reaction
Kb =(HCO3-)(OH-)/CO3^-2
kb=2 .0 x 10^-4
the concentration of both HCO3- and OH- can be presented by X
therefore KB= (x)(x)/(CO3^-2)
2.0 x 10 ^-4 =(x)(x)/0.125
multiply both side by 0.125
=2.5 x10^-5=(x^2)
find square root
x=5 x 10^-3
