17. Calcium sulfate has a soluble form in water, formed according to: Ca 2+ (aq) + SO4 2- (aq) ?CaSO 4 (aq) K = 7.7×103 CaSO 4 (s) itself, however, is poorly soluble and has the following solubility product: CaSO 4 (s) ?Ca 2+ (aq) + SO4 2- (aq) Ksp = 3×10-34 If we dissolve CaSO 4 (s) in water until CaSO 4 (s)precipitate is left in equilibrium with the solution, (a)        What is the concentration of Ca 2+ (aq)? (b)       What is the concentration of the soluble complex CaSO 4 (aq)? Solution Ksp = [M] 2 where [M] is concentration of Ca 2+ (aq) and SO4 2- (aq) . [M] = (3x10 -34 ) 0.5 = 1.73x10 -17 K = [CaSO 4 (aq) ] /([Ca 2+ (aq) ]x[SO4 2- (aq)]) 7.7x10 3 x ([M] 2 )= [CaSO 4 (aq) ] 7.7x10 3 x3x10 -34 = [CaSO 4 (aq) ] [CaSO 4 (aq) ] = 23.1 x 10 -31 .