A generic salt AB3 has a molar mass of 263 gmol and a solubi

A generic salt, AB3, has a molar mass of 263 g/mol and a solubility of 1.70 g/L at 25 °C. What is the Ksp of this salt at 25 °C?

Solution

Molar mass of AB3= 263 g/mol
s = 1.7 g/L
To covert it to mol/L, divide it by molar mass
s = 1.7 g/L / 263 g/mol
s = 6.464*10^-3 g/mol

At equilibrium:
AB3       <---->     A3+      +         3 B-    

                     s                  3s      

Ksp = [A3+][B-]^3
Ksp = (s)*(3s)^3
Ksp = 27(s)^4
Ksp = 27(6.464*10^-3)^4
Ksp = 4.713*10^-8
Answer: 4.71*10^-8