How to write solubility equilibrium and solubility-product constant expression?

Equilibrium problem help?

• For each of the following substances, write the solubility product expression and calculate the Ksp in pure water: A. 1.04 g MgC2O4 in 1.00 L pure water B. 55.0 mg Ag2CrO4 in 2.50 L pure I know the solubility product equations, I just don't know how to calculate the Ksp. Thanks for the help!!

• Answer:

  Inorder to calculate Ksp, you need to calculate the molar concentration of the ions formed from the compound. 1.04 g MgC2O4 / 112.4 g/mol = 9.25X10^-3 mol /L So, Ksp = [Mg2+][C2O42-] = (9.25X10^-3)(9.25X10^-3) = 8.36X10^-5 B. 0.055 g/2.5L = 0.022 g/L / 331.7 g/mol = 6.63X10^-5 M. Now, when this dissolves, it produces 2 Ag+ ions, so, [Ag+] = 1.33X10X10^-4 M, and [CrO42-] = 6.63X10^-5 M So, Ksp = [Ag+]^2]CrO42-] = (1.33X10^-4)^2(6.63X10^-5 = 1.17X10^-12