Here's how to calculate the number of molecules of sulfur tetrafluoride (SF₄) in 2.13 moles:

1. Avogadro's Number

* Avogadro's number tells us the number of particles (atoms, molecules, etc.) in one mole of a substance. It's approximately 6.022 x 10²³ particles/mole.

2. Calculation

* Step 1: Multiply the number of moles of SF₄ by Avogadro's number:

2.13 moles SF₄ * (6.022 x 10²³ molecules SF₄ / 1 mole SF₄)

* Step 2: The "moles SF₄" units cancel out, leaving you with:

1.28 x 10²⁴ molecules SF₄

Answer: There are approximately 1.28 x 10²⁴ molecules of sulfur tetrafluoride in 2.13 moles of the compound.