Consider a solution containing Hg2 and Fe2 both at molaritie

Consider a solution containing Hg²⁺ and Fe²⁺, both at molarities of 0.011 M. It is to be saturated with H₂S (where [H₂S] = 0.1 M). Calculate the highest pH that this solution could have that would keep Fe²⁺ in solution while causing Hg²⁺ to precipitate as HgS.
pH =

Solution

ksp of HgS=2*10^-53

so ,

[0.011]*s=2*10^-53

or s=1.82*10^-51 M.so,

[H+] due to the acid be x.so,

x=2s

=3.64*10^-51 M

so [H]=10^-7+3.64*10^-52

or pH~7