Overview
This lecture introduces Avogadro's Constant and the mole as key units for counting particles in chemistry, relating them to real-world counting units and their significance for atomic and molecular mass calculations.
Units as Counting Tools
- Everyday units like "pair" (2) and "dozen" (12) are used to count objects.
- The mole is a counting unit in chemistry, representing a much larger number: 6.022 × 10²³ particles.
Avogadro's Constant and the Mole
- Avogadro's Constant (6.022 × 10²³) is the number of particles in one mole of a substance.
- The mole allows chemists to work with manageable quantities instead of individual atoms or molecules.
Mass and the Mole
- The mass of one mole of an element (in grams) equals its atomic weight from the periodic table.
- 1 mol of vanadium (V) = 6.022 × 10²³ atoms = 50.9415 grams.
- 1 mol of magnesium (Mg) = 6.022 × 10²³ atoms = 24.305 grams.
- Different elements have different molar masses, just as a dozen baseballs and a dozen softballs have different masses.
Compounds and Molecular Weight
- For compounds, 1 mole = molecular weight in grams.
- 1 mol of CO₂ = 6.022 × 10²³ molecules = 44.0 grams.
- The distinction between atoms (elements) and molecules (compounds) is essential for understanding chemical reactions.
Key Terms & Definitions
- Mole — A unit representing 6.022 × 10²³ particles (atoms, molecules, etc.).
- Avogadro's Constant — The numerical value 6.022 × 10²³, representing the number of particles in a mole.
- Atomic Weight — The mass (in grams) of one mole of an element's atoms, as listed on the periodic table.
- Molecular Weight — The mass (in grams) of one mole of a compound's molecules.
Action Items / Next Steps
- Review atomic and molecular weights on the periodic table.
- Prepare for discussion on the distinction between atoms and molecules in the next lecture.