1. Understand the Formula

* BaSO₄ represents barium sulfate. The subscript "4" after the oxygen (O) indicates that there are four oxygen atoms in each molecule of barium sulfate.

* Importantly, the subscript "1" is implied for barium (Ba) and sulfur (S), meaning there is one atom of each in every molecule.

2. Avogadro's Number

* Avogadro's number is 6.022 x 10²³ and represents the number of particles (atoms, molecules, etc.) in one mole of a substance.

3. Calculation

* Step 1: Since there is one sulfur atom per molecule of barium sulfate, we know that 0.45 mol of BaSO₄ contains 0.45 mol of sulfur atoms.

* Step 2: To find the number of sulfur atoms, multiply the moles of sulfur atoms by Avogadro's number:

0.45 mol S × (6.022 x 10²³ atoms S / 1 mol S) = 2.71 x 10²³ sulfur atoms

Therefore, there are approximately 2.71 x 10²³ sulfur atoms in 0.45 mol of BaSO₄.