Balancing Chemical Equations Lecture Notes

Introduction

• Balancing chemical equations is a challenging concept in chemistry.
• It requires careful and methodical approach.

What is a Chemical Equation?

• A chemical equation describes a chemical reaction.
• Example: Reaction of aluminum with dioxygen to form aluminum oxide:
  • Reactants: Aluminum (Al), Dioxygen (O₂)
  • Product: Aluminum oxide (Al₂O₃)

Balancing Equations

• Objective: Ensure the number of atoms of each element is the same on both sides of the equation.
• Example problem:
  • Left side: 1 Aluminum, 2 Oxygens
  • Right side: 2 Aluminums, 3 Oxygens

Steps to Balance

1. Aluminum Balance:
   • Left: 1 Al → Right: 2 Al
   • Solution: Place a '2' in front of Aluminum on the left.
   • Adjusted Aluminum balance:
     • Left: 2 Al
     • Right: 2 Al
2. Oxygen Balance:
   • Left: 2 O (as O₂) → Right: 3 O
   • Solution: Multiply Oxygens by 1.5 on the left to match the right.
   • We prefer whole numbers, so avoid fractional molecules.

Avoiding Fractions

• Multiplying both sides of the equation by 2 helps in eliminating fractions:
  • Adjust factors:
    • Aluminum: 2 × 2 = 4
    • Dioxygen: 1.5 × 2 = 3
    • Aluminum Oxide: 1 × 2 = 2

Final Balanced Equation

• Chemical Equation: (4Al + 3O_2 → 2Al_2O_3)
• Verify:
  • Aluminums:
    • Left: 4
    • Right: 4
  • Oxygens:
    • Left: 6 (3 O₂ molecules)
    • Right: 6 (2 Al₂O₃ molecules)

Conclusion

• Balanced chemical equations ensure conservation of mass.
• This requires an equal number of each type of atom on both sides of the equation.
• Balancing chemical equations is like solving algebraic equations by ensuring balance across the equation.