Answer:
2.546 * 10^23 atoms of P2O5
Explanation:
Number of moles in 120.0 g of P2O5 =mass/ molar mass = 120.0 g/283.886 g/mol= 0.423 moles
1 mole of P2O5 contains 6.02 * 10^23 atoms
hence 0.423 moles of P2O5 will contain 0.423 * Â 6.02 * 10^23 /1 = 2.546 * 10^23 atoms of P2O5