Question #885cc

1 Answer
Apr 27, 2015

[OH^-][OH] =10^-5105

From KspKsp of Cu(OH)_2Cu(OH)2, it starts precipitating at:
2.2*10^-202.21020 = [Cu^(2+)][Cu2+]*[OH^-]^2[OH]2
[OH^-][OH]=sqrt (0.22*10^-20)0.221020=0.46*10^(-10)0.461010

and from KspKsp of Mg(OH)_2Mg(OH)2, it starts precipitating at
6.3*10^-106.31010 =[Mg^(2+)][Mg2+]*[OH^-]^2[OH]2
[OH^-][OH]=sqrt (1.26*10^-10)1.261010 =1.12*10^(-5)1.12105

therefore at [OH^-][OH]=10^(-5)105 all Cu(OH)_2Cu(OH)2 is precipitated and all Mg(OH)_2Mg(OH)2 is in solution