What is the concentration of Ca2+ in this solution if [OH-] is fixed at 3.00*10^-4 M?

Question

Hydroxyapatite, Ca10(PO4)6(OH)2 has a solubility constant of Ksp= 2.34*10^-59 and dissociates according to:

Ca10(PO4)6(OH)2 (s)—> 10Ca 2+ (aq) + 6PO4 3- (aq) + 2 OH- (aq). Solid hydroxyapatite is dissolved in water to form a saturated solution. What is the concentration of Ca2+ in this solution if [OH-] is fixed at 3.00*10^-4 M?

(by the way the answer is not 6.16* 10^-4 M)

Any help would be appreciated, thank you!!

Answer 1

Is the answer 7.23x10^-4 M? If so, I’’ll provide the workings. If not, no sense in showing incorrect calculations. Please comment.