Final answer:
To calculate the number of moles of Sr3P2 from 5.53 × 10^25 atoms, divide the number of atoms by the number of atoms per formula unit, and then by Avogadro's number, resulting in 18.36 moles.
Step-by-step explanation:
To determine the number of moles of Sr3P2 in 5.53 × 1025 atoms, you need to use Avogadro's number, which is 6.022 × 1023 atoms per mole. First, divide the total number of atoms by the number of atoms per formula unit of Sr3P2, which is 3 Sr atoms + 2 P atoms = 5 atoms per formula unit. Then, divide that result by Avogadro's number to find the number of moles.
Number of formula units in the sample = 5.53 × 1025 atoms / 5 atoms per formula unit = 1.106 × 1025 formula units.
Number of moles of Sr3P2 = 1.106 × 1025 formula units / 6.022 × 1023 formula units per mole = 18.36 moles.