Question

The solubility of calcium sulfate at a given temperature is 0.02005 g/L. Calculate the Ksp at this temperature. After you get your answer, take the negative log and enter that (so it's like you're taking the pKsp). (Note: sulfate ion molar mass = 96.07 g/mol)

Answer 1

If we assume a Liter of water.

Moles of CaSO4 = mass / molar mass = 2.005 * 10-2 / 136 = 1.474 * 10-4 M

The equation for dissolution is: CaSO4 $\rightleftharpoons$ Ca2+ + SO42-

From the equation: [Ca2+] = [SO42-] = 1.474 * 10-4 M

Using this in the equation for Ksp = [Ca2+] * [SO42-] = 1.474 * 10-4 * 1.474 * 10-4 = 2.173 * 10-8 M2

uisng negative log, we get: 7.663