Chem
posted by Josh .
How many oxygen atoms do you have in 2.00 grams of calcium phosphate?
Do you use avogadro's number and how?
How many Ca^2+ ions do you have in 2.00 grams of calcium phosphate?
Any help would be greatly appreciated.

The formula for calcium phoshpate is
Ca3(PO4)2. First calculate the molar mass of that molecule. It is about 3x40 + 2x31 + 8x16 = 310 g/mol. You can get a more accurate value using more significant figures for ate atomic weights.
2 grams of the compound is only 2/31 mole. Multiply that by Avogadro's number for the number of molecules. There are 3 Ca2+ ions per molecule and 8 O atoms per molecule.