Lecture Notes: Mole Ratios and Applications

Introduction to Mole Ratios

• Definition: A mole ratio indicates the number of moles of one substance in relation to another.
• Sources of Mole Ratios:
  • Chemical Formulas: Derived from subscripts in formulas.
  • Balanced Chemical Equations: Derived from coefficients in reactions.

Mole Ratios in Chemical Formulas

• Example: Magnesium Nitrate (Mg(NO₃)₂)
  • Contains 1 Magnesium ion and 2 Nitrate ions.
  • For every 1 mole of magnesium nitrate, there are 3 moles of ions.
  • Specific Mole Ratios:
    • 2 moles of nitrate to 1 mole of magnesium.
    • 6 moles of oxygen to 1 mole of magnesium nitrate.

Mole Ratios in Balanced Equations

• Example: Reaction of C₂H₆ with O₂
  • Reaction: 2 C₂H₆ + 7 O₂ → 4 CO₂ + 6 H₂O
  • Mole Ratios:
    • 2 moles C₂H₆ : 7 moles O₂
    • 4 moles CO₂ : 6 moles H₂O
    • Ratios can be used across the equation:
      • 7 moles O₂ : 4 moles CO₂
      • 6 moles H₂O : 2 moles C₂H₆

Calculating Atoms and Ions Using Mole Ratios

1. Calculating Hydrogen Atoms in 59.3 g of Water:

   • Water Formula: H₂O
   • Molar Mass of Water: 18.02 g/mol
   • Convert grams to moles, then moles to atoms using Avogadro's number.
   • Result: 3.96 x 10²⁴ hydrogen atoms.

2. Calculating Nitrate Ions in 3.99 g of Aluminum Nitrate:

   • Formula: Al(NO₃)₃
   • Molar Mass: 213.0 g/mol
   • Convert to moles, calculate moles of nitrate ions, then use Avogadro's number.
   • Result: 3.38 x 10²² nitrate ions.

3. Calculating Ions in 15 g of Ammonium Carbonate:

   • Formula: (NH₄)₂CO₃
   • Molar Mass: 96.09 g/mol
   • Recognize that 1 mole of ammonium carbonate contains 3 moles of ions.
   • Result: 2.82 x 10²³ ions.

Conclusion and Study Tips

• Review objectives and chapter focus.
• Additional practice problems and solutions are available online.
• Textbook and video resources are available for further study.