How many total atoms are in 0.400 g of P2O5?

To find the total number of atoms in 0.400 g of P₂O₅, first calculate the molar mass of P₂O₅, which is approximately 283.88 g/mol (with phosphorus (P) at about 30.97 g/mol and oxygen (O) at about 16.00 g/mol). Then, determine the number of moles in 0.400 g by dividing the mass by the molar mass: (0.400 , \text{g} \div 283.88 , \text{g/mol} \approx 0.00141 , \text{mol}). Since each molecule of P₂O₅ contains 7 atoms (2 phosphorus + 5 oxygen), multiply the moles by Avogadro's number (approximately (6.022 \times 10^{23}) atoms/mol) and then by 7, resulting in approximately (5.89 \times 10^{21}) total atoms.