1. Use the following data to calculate the K sp value for each solid.
(a) The solubility of FeCO 3 is 5.6???10 ?4
g/L.
(b) The solubility of Al(OH) 3 is 5.5???10 ?9
mol/L.
Solution
a)
FeCO3 <--> Fe+2 + CO3-2
s s
molar mass of FeCO3 = 115.9 g/mol
s = (5.6*10^-4)/(molar mass of FeCO3)
= (5.6*10^-4)/115.9
= (4.83*10^-6)
Ksp = [Fe+2]*[CO3-2]
= s*s
= s^2
= (4.83*10^-6)^2
= 2.33*10^-11
b)
Al(OH)3 <--> Al+3 + 3OH-
s 3s
Ksp = [Al+3]*[OH-]^3
= s*(3s)^3
= 27*s^4
= 27*(5.5*10^-9)^4
= (2.47*10^-32)