Understanding Stoichiometry through Examples

Aug 5, 2024

Stoichiometry Lecture Notes

Introduction to Stoichiometry

  • Types of Conversion Factors:
    1. Molar Mass: Used for converting between grams and moles.
    2. Mole Ratio: Found in balanced equations for converting between different compounds.
    3. Avogadro's Number: Used for calculations involving atoms, molecules, particles, and formula units.

Example 1: Hydrogen Peroxide and Water

  • Problem Statement: What mass of hydrogen peroxide decomposes to produce 48.64 grams of water?
  • Given Information:
    • 48.64 grams of water (H2O)
    • Hydrogen peroxide (H2O2)
  • Balanced Equation Needed:
    • H2O2 decomposes to H2O.

Steps to Solve:

  1. Convert Grams of Water to Moles:
    • Use molar mass of water (18.02 g/mol).
  2. Use Mole Ratio from Balanced Equation:
    • 2 moles of H2O for every 2 moles of H2O2.
  3. Convert Moles of H2O2 to Grams:
    • Use molar mass of hydrogen peroxide to find grams.

Calculation Example:

  • Start with 48.64 g H2O.
  • Convert to moles:
    • (48.64 g H2O) * (1 mol/18.02 g) = moles H2O.
  • Mole ratio from balanced equation:
    • 2 moles H2O2 / 2 moles H2O.
  • Convert to grams of H2O2:
    • (moles H2O2) * (34.02 g/mol H2O2) = grams H2O2.
  • Final Result:
    • 91.83 grams of hydrogen peroxide.

Example 2: Carbon Dioxide and Carbon Monoxide

  • Problem Statement: How many molecules of CO2 are required to react with 174 grams of CO?
  • Given Information:
    • 174 grams of carbon monoxide (CO)
    • Carbon dioxide (CO2)
  • Balanced Equation Needed:
    • CO + O2 → CO2

Steps to Solve:

  1. Convert Grams of CO to Moles:
    • Use molar mass of carbon monoxide (28.01 g/mol).
  2. Use Mole Ratio from Balanced Equation:
    • 2 moles of CO produces 2 moles of CO2.
  3. Convert Moles of CO2 to Molecules:
    • Use Avogadro's number (6.022 x 10^23 particles/mol).

Calculation Example:

  • Start with 174 g CO.
  • Convert to moles:
    • (174 g CO) * (1 mol/28.01 g) = moles CO.
  • Mole ratio from balanced equation:
    • 2 moles CO2 / 2 moles CO.
  • Convert to molecules of CO2:
    • (moles CO2) * (6.022 x 10^23 molecules/mol) = molecules CO2.
  • Final Result:
    • 3.74 x 10^24 molecules of CO2.

Conclusion

  • Practice is important to gain a deeper understanding of stoichiometry.
  • More examples and practice problems are available in additional resources.
  • Questions can be left in the comments for further clarification.