Academic Integrity: tutoring, explanations, and feedback — we don’t complete graded work or submit on a student’s behalf.

(A) Calculate the solubility in moles/liter (M) for Ba3(PO4)2 in pure water (Ksp

ID: 1810720 • Letter: #

Question

(A) Calculate the solubility in moles/liter (M) for Ba3(PO4)2 in pure water (Ksp = 6.0 x 10^-39.) (Ignore any acid/base behavior)
(B) Determine the equilibrium expression that enables calculation of the solubility (S) in
moles/liter (M) for Ba3(PO4)2 in 1.0 x 10^-3 M BaCl2 and calculate the solubility.
(Ignore any acid/base behavior).
(C)Determine the equilibrium expression that enables calculation of the solubility (S) in moles/liter (M) for Ba3(PO4)2 in 2.5 x 10^-2 M Na3PO4. Also, calculate the solubility.

Explanation / Answer

Step 1. Write out the Ksp reaction and expression for Ksp, i.e.

Ba3(PO4)2 (s) --> 3Ba2+ (aq) + 2(PO4)3- (aq)
Ksp = [Ba]^3 * [PO4]^2

Remember that Ksp is just an equilibrium constant just like any other. Products over reactants, with each entity raised to the power of its coefficient. In this case the reactant is a solid, and thus entered as 1, so we ignore it.

Step 2. Let x = concentration of Ba3(PO4)2 that will dissolve in water. Now go back to your balanced equation. For every x mol of the solid that dissolve, you get 3x mol barium and 2x mol PO4. Substitute into your Ksp equation, i.e.

Ksp (given in problem) = (3x)^3 * (2x)^2

Solve this equation for x and you have your molar solubility of barium phosphate