[winterfrostx]

I have a couple of questions about K_sp problems...
1. What is the equilibrum concentration of silver ions at 25 degrees Cel. in a 1.0-L saturated solution of silver carbonate to which 0.20 mol of Na₂CO₃ has been added? The K_sp of Ag₂Co₃ is 8.1*10^-12 at 25 degrees Cel.

Are we trying to find the concentration of Ag₂ as a whole? or just one of the ions?

This is what I did so far:

Ag₂Co₃<--->2Ag²+ + CO₃^2-
K_sp = 8.1 x 10^-12 = [Ag⁺]² * [CO₃^-] = [Ag⁺]² * (0.20)
---
4.05 x 10^-11 = [Ag]²
I just don't know if this is where I should end it. Should I square root both sides to find the concentration of a single silver ion?

2. Is there a way to rank salts from most soluble to least soluble without knowing their K_sp values? (such as only using the solubility rules? or are the rules only there to tell you simply if the salt is soluble or not?)
ex) List these from most soluble to least soluble:
CuS, BaSO₄, SrCO₃, AgI

Thanks!!

[Jorriss]

For two, I don't know any hard fast rules, I only know the answers through experience in labs.

For one, it is not that easy. It's a molar solubility problem if I am thinking correctly.

[AWK]

1.
http://www.cartage.org.lb/en/themes/sciences/chemistry/miscellenous/helpfile/PrecipitationEquilibrium/CommonIonEffect.htm