Answer :
To find the number of atoms in each sample, divide the mass given by the molar mass of the element to get moles, and then multiply by Avogadro's number. The calculations yield approximately 1.16 × 10²³ atoms for Sr, 2.81 × 10²³ atoms for Fe, 2.47 × 10²² atoms for Bi, and 7.40 × 10²³ atoms for P. This method applies the concept of moles and Avogadro's number to determine the count of atoms.
Here's the detailed calculation for each element:
Strontium (Sr): Molar mass = 87.62 g/mol
Number of moles = 16.9 g / 87.62 g/mol ≈ 0.193 mol
Number of atoms = 0.193 mol × 6.022 × 10²³ atoms/mol ≈ 1.16 × 10²³ atoms
Iron (Fe): Molar mass = 55.85 g/mol
Number of moles = 26.1 g / 55.85 g/mol ≈ 0.467 mol
Number of atoms = 0.467 mol × 6.022 × 10²³ atoms/mol ≈ 2.81 × 10²³ atoms
Bismuth (Bi): Molar mass = 208.98 g/mol
Number of moles = 8.55 g / 208.98 g/mol ≈ 0.041 mol
Number of atoms = 0.041 mol × 6.022 × 10²³ atoms/mol ≈ 2.47 × 10²² atoms
Phosphorus (P): Molar mass = 30.97 g/mol
Number of moles = 38.2 g / 30.97 g/mol ≈ 1.23 mol
Number of atoms = 1.23 mol × 6.022 × 10²³ atoms/mol ≈ 7.40 × 10²³ atoms
