A popular lecture demonstration involves the sequential precipitation and dissolution of several slightly soluble silver compounds beginning with a
[Ag+] = 0.0050 M. Use the information below to answer the following questions about this demonstration.
Ag2SO4 = 1.4×10^(-5)
What must the [SO4^(2-)] be in order to start precipitation in a solution in which [Ag+] = 0.005 M?
`Ag_2SO_4 rarr 2Ag^++SO_4^(2-)`
By the `K_(sp)` notation we can write;
`K_(sp) = [Ag^+]^2[SO_4^(2-)]`
`1.4xx10^(-5) = (0.005)^2[SO_4^(2-)]`
`[SO_4^(2-)] = (1.4xx10^(-5))/(25xx10^(-6))`
`[SO_4^(2-)] = 0.56M`
So we need 0.56M of sulphate ion concentration in order to precipitate `Ag_2SO_4`