Question

Calculating Molar Solubility:

Part 1: Calculate the molar solubility of CaSO4 in pure water. Ksp for CaSO4 = 2.4 x 10-5 Part 2: Calculate the molar solubility of CaSO4 in a solution containing 0.100 M Na2SO4.

(Please show all work! will upvote.)

Answer 1

CaSO4 in solution dissociates as follows: CaSO4< => Ca2+ + SO4 2- and; the Ksp equation: Ksp = [Ca 2+] [SO4 2+] given that the Ksp = 2.4*10^-5 Assume tha the solubility is S Therefore 2.4*10^-5 =S*S S^2 = 2.4*10^-5 S=4.90*10^-3 M [Na2SO4) = 0.100 M , Which is equal to the [SO42-] now use the [SO4 2-1 from the Na2SO4 = 0.100M and as compare of this amount of SO42- From sodium sulfate , we can ignore the small amount of SO4 2- ions from the remaining dissociation of the CaSO4 because this is so small compared to the 0.1000M from the Na2SO4 Substitute: 2.4*10^-5 = [Ca 2+1 * 0.100 [Ca2+] = (2.4*10^-5)/0.100 [Ca2+] = 2.4*10^-4 M