Question

Calcium oxalate (CaC2O4) has a Ksp value of 2.3 × 10–9 at 25°C. Calculate the molar solubility of Ca2+ and C2O42– in one liter of aqueous solution.

Ksp = [X] × [X]

What is the molar solubility of Ca2+?

2.3 x 10-9 M

4.8 x 10–5 M

4.60 x 10-9 M

5.29 x 10-18 M

Answer 1

the KSP gives you the ratio of the ions, where your X values are the concentrations of the ions that are dissolved. Since the two ions are in a 1:1 ratio in the compound, their individual concentrations will be equal to each other. The KSP equation set up properly looks like this:
\[K_{SP} = [Ca^{+2}][C_2O_4^{-2}] = 2.3*10^{-9}\]take the square root of the KSP and you'll have the concentration of calcium ions

Answer 2

Okay thank you! Could you help me with this one too?

In each of the following reactions, Ksp = 1.00. Which reaction would have the highest molar solubility?
W <->X + 2Y + 3Z

W<->2X + 2Y + 2Z

W <->3X + 3Y

W<->6X