Using Avogadro's Constant to Calculate the Number of Molecules and Atoms

Introduction

• Target Audience: Higher students only.
• Focus: Calculate the number of molecules and atoms using Avogadro's Constant.
• Disclaimer: Material is challenging; perseverance is encouraged.

Review of Moles and Avogadro's Constant

• Moles: Previously discussed as a way to express quantities in chemistry.
• Avogadro's Constant:
  • Value: (6.02 \times 10^{23})
  • Represents the number of entities (atoms, molecules) in one mole.

Calculating Moles of Atoms in Molecules

Example 1: Water (H₂O)

• Calculation:
  • 1 molecule of H₂O = 2 hydrogen (H) + 1 oxygen (O) = 3 atoms
  • Therefore, 1 mole of H₂O = 3 moles of atoms.

Example 2: Methane (CH₄)

• Exercise for Audience:
  • 1 molecule of CH₄ = 1 carbon (C) + 4 hydrogen (H) = 5 atoms
  • Hence, 1 mole of CH₄ = 5 moles of atoms.

Example 3: Calcium Hydroxide (Ca(OH)₂)

• Solution:
  • 1 molecule of Ca(OH)₂ = 1 calcium (Ca) + 2 oxygen (O) + 2 hydrogen (H) = 5 atoms
  • Therefore, 1 mole of Ca(OH)₂ = 5 moles of atoms.

Using Avogadro's Constant to Calculate Atoms

Example 1: Hydrogen Chloride (HCl)

• Calculation:
  • 1 molecule of HCl = 1 hydrogen (H) + 1 chlorine (Cl) = 2 atoms
  • 1 mole of HCl = (6.02 \times 10^{23}) molecules = (2 \times 6.02 \times 10^{23} = 1.24 \times 10^{24}) atoms.

Example 2: Sodium Oxide (Na₂O)

• Exercise for Audience:
  • 1 molecule of Na₂O = 2 sodium (Na) + 1 oxygen (O) = 3 atoms
  • 1 mole of Na₂O = (6.02 \times 10^{23}) molecules = (3 \times 6.02 \times 10^{23} = 1.86 \times 10^{24}) atoms.

Additional Resources

• Revision Workbook: Additional questions available for practice.
• Next Steps: Upcoming video will cover more complex applications of Avogadro's Constant.

These notes summarize the key points from the lecture on Avogadro's Constant, providing formulas and example calculations for better understanding.