How many calcium ions are in a sample of 7.36 grams of calcium phosphate?

5.72 x 10^22. There are 5.72 x 10^22 Ca^ (2+) ions in 7.36 g Ca3 (PO4) 2.

a) Moles of Ca3 (PO4) 2

MM of Ca3 (PO4) 2 = [3x40.08 + 2 (30.97 + 4x16.00) ] g/mol

= (120.24 + 2x94.97) g/mol = (120.24 + 189.94) g/mol = 310.18 g/mol

Moles of Ca3 (PO4) 2

= 7.36 g Ca3 (PO4) 2 x [1 mol Ca3 (PO4) 2]/[310.18 g Ca3 (PO4) 2]

= 0.023 73 mol Ca3 (PO4) 2

b) Formula units (FU) of Ca3 (PO4) 2

Formula units of Ca3 (PO4) 2

= 0.023 73 mol Ca3 (PO4) 2 x [6.022 x 10^23 FU Ca3 (PO4) 2]/[1 mol Ca3 (PO4) 2] = 1.429 x 10^22 FU Ca3 (PO4) 2

c) Ions of Ca

No. of Ca ions

= 1.429 x 10^22 FU Ca3 (PO4) 2 x [4 Ca^ (2+) ions]/[1 FU Ca3 (PO4) 2]

= 5.72 x 10^22 Ca^ (2+) ions