In 12.5g of Mg3(PO4)2 : how many total atoms & how many P atoms?

Answer 1

Find number of moles from molar mass: [12.5g Mg₃(PO₄)₂] * [1 mole Mg₃(PO₄)₂ / 262.9g Mg₃(PO₄)₂] = 0.0475₅ mole Mg₃(PO₄)₂. Then (0.0475₅ mole) * (6.022 x 10²³ molecules/ 1 mole) = 2.86₄ x 10²² molecules. Total atoms in 12.5g = (2.86₄ x 10²² molecules) * (13 atoms/molecule) = 3.72 x 10²³ atoms; P atoms = (2.86₄ x 10²² molecules) * (2 P atoms/molecule) = 5.73 x 10²² P atoms.