1)_ 500ml solution is prepared by dissolving 2560mg Ca3(PO4)2 in enough water. Calculate the value of pCa accordingly?

Answer 1

I don't know who made up this problem but you will have trouble trying to dissolve 2.56 g Ca3(PO4)2 in "enough" water. It will take a lot of water.
mols Ca3(PO4)2 = grams/molar mass = ?
Then M Ca3(PO4)2 = mols/0.500 L = ?
Then M Ca will be 3x the molarity of Ca3(PO4)2
Then pCa = - log(Ca^2+)