Molar Solubility?

Question

Calculate the molar solubility of SrCO3 (Ksp = 5.4 10-10) in each of the following.
0.14 M Sr(NO3)2

Answer 1

Let X (M) be the molar solubility of SrCO3 (Ksp = 5.4 10-10) in 0.14 M Sr(NO3)2.
SrCO3(s) <==> Sr(2+) + CO3(2-)
---------------------(0.14+X)------X
X(0.14+X) = Ksp = 5.4x10^-10
or X^2 + 0.14X - 5.4x10^-10 = 0
Solve this quadratic equation or simply let 0.14+X ≈ 0.14 since X is very small, we get the molar solubility of SrCO3 in 0.14 M Sr(NO3)2 as X = 3.9x10^-9M.