To determine the number of atoms in a given mass of a compound, you need to use the concept of moles and Avogadro's number. Avogadro's number (symbolized as Nₐ) is approximately 6.022 × 10^23, and it represents the number of atoms or molecules in one mole of a substance.
First, we need to find the number of moles of CaCO₃ in 20 g. To do this, we divide the given mass by the molar mass of CaCO₃.
The molar mass of CaCO₃ is: (1 × atomic mass of Ca) + (1 × atomic mass of C) + (3 × atomic mass of O) = (1 × 40.08 g/mol) + (1 × 12.01 g/mol) + (3 × 16.00 g/mol) ≈ 100.09 g/mol
Number of moles = Mass (g) / Molar mass (g/mol) Number of moles = 20 g / 100.09 g/mol ≈ 0.1999 moles
Now, to find the number of atoms, we multiply the number of moles by Avogadro's number: Number of atoms = Number of moles × Avogadro's number Number of atoms = 0.1999 moles × (6.022 × 10^23 atoms/mol) ≈ 1.204 × 10^23 atoms
Therefore, there are approximately 1.204 × 10^23 atoms in 20 g of CaCO₃.