Lecture Notes: Conversion Factors and Mole Ratios

Key Concepts

• Conversion Factors: Tools for converting units by canceling out unwanted units.

  • Example: Converting lenses per spider or hands per person to total lenses or hands.
  • Use the correct fraction of the conversion factor to ensure units cancel out properly.

• Chemical Formulas and Mole Ratios:

  • Mole ratios are derived from chemical formulas and help determine the amount of elements in a compound.
  • Example: Calcium carbonate (CaCO) consists of calcium, carbon, and oxygen.
  • Mole ratio from formula: 1 mole of CaCO contains 1 mole of calcium, 1 mole of carbon, and 3 moles of oxygen.

Example Problems

Problem 1: Moles of Oxygen in Calcium Carbonate

• Objective: Determine moles of oxygen in 1.7 moles of calcium carbonate.
• Mole Ratio: 1 mole of CaCO = 1 mole of Ca = 1 mole of C = 3 moles of O
• Solution: Use the mole ratio to find oxygen moles.

Problem 2: Mass of Sodium in Sodium Chloride

• Objective: Convert grams of sodium to grams of sodium chloride.
• Steps:
  1. Begin with the given mass of sodium (e.g., 2.4 grams).
  2. Convert grams to moles using the conversion factor: 1 mole Na = 22.99 grams Na.
  3. Use mole ratio: 1 mole NaCl = 1 mole Na.
  4. Convert moles of sodium chloride back to grams using the conversion factor: 1 mole NaCl = 58.44 grams NaCl.
• Result: Calculate the mass in grams of sodium chloride.

Important Notes

• Converting between grams of two substances requires an intermediate conversion to moles.
• Key Conversion Factors:
  • Grams to Moles: Use molar mass for conversion.
  • Moles to Grams: Utilize the molar mass for the specific compound.

Study Tips

• Practice problems to master conversion processes.
• Review chapters 2 and 6 for better understanding of conversions and mole calculations.
• Seek help if you encounter difficulties in applying concepts or solving problems.