Lecture: Balancing Chemical Equations

Introduction

• Practice problems for balancing chemical equations.
• Start with basic examples and progress to more challenging problems.

Example 1: Xenon and Fluorine

• Equation: ( \text{Xe} + \text{F}_2 \rightarrow \text{XeF}_6 )
• Atoms Count:
  • Left: 1 Xenon, 2 Fluorine
  • Right: 1 Xenon, 6 Fluorine
• Balancing:
  • Add a coefficient of 3 to ( \text{F}_2 ) to have 6 Fluorine on the left.
  • Balanced: 1 Xenon, 6 Fluorine.
• Note: Cannot change subscripts, only coefficients._

Example 2: Silver, Hydrogen, and Sulfur

• Equation: ( \text{Ag} + \text{H}_2\text{S} \rightarrow \text{Ag}_2\text{S} + \text{H}_2 )
• Atoms Count:
  • Left: 1 Silver, 2 Hydrogen, 1 Sulfur
  • Right: 2 Silver, 2 Hydrogen, 1 Sulfur
• Balancing:
  • Add a coefficient of 2 to ( \text{Ag} ) on the left.
  • Balanced: 2 Silver, 2 Hydrogen, 1 Sulfur._

Example 3: Potassium, Oxygen, Hydrogen, and Carbon

• Equation: ( \text{KOH} + \text{CO}_2 \rightarrow \text{K}_2\text{CO}_3 + \text{H}_2\text{O} )
• Atoms Count:
  • Left: 1 Potassium, 3 Oxygen, 1 Hydrogen, 1 Carbon
  • Right: 2 Potassium, 4 Oxygen, 2 Hydrogen, 1 Carbon
• Balancing:
  • Add a coefficient of 2 to ( \text{KOH} ) on the left.
  • Balanced: 2 Potassium, 4 Oxygen, 2 Hydrogen, 1 Carbon.

Multi-step Balancing Examples

Example 4: Sodium and Chlorine

• Equation: ( \text{Na} + \text{Cl}_2 \rightarrow \text{NaCl} )
• Atoms Count:
  • Left: 1 Sodium, 2 Chlorine
  • Right: 1 Sodium, 1 Chlorine
• Balancing:
  • Add a coefficient of 2 to ( \text{NaCl} ) on the right.
  • Add a coefficient of 2 to ( \text{Na} ) on the left.
  • Balanced: 2 Sodium, 2 Chlorine._

Example 5: Iron, Oxygen, and Carbon

• Equation: ( \text{FeO} + \text{C} \rightarrow \text{Fe} + \text{CO}_2 )
• Atoms Count:
  • Left: 1 Iron, 1 Oxygen, 1 Carbon
  • Right: 1 Iron, 2 Oxygen, 1 Carbon
• Balancing:
  • Add a coefficient of 2 to ( \text{FeO} ) on the left and ( \text{Fe} ) on the right.
  • Balanced: 2 Iron, 2 Oxygen, 1 Carbon._

Example 6: Silicon, Oxygen, and Carbon

• Equation: ( \text{SiO}_2 + \text{C} \rightarrow \text{Si} + \text{CO} )
• Atoms Count:
  • Left: 1 Silicon, 2 Oxygen, 1 Carbon
  • Right: 1 Silicon, 1 Oxygen, 2 Carbon
• Balancing:
  • Add a coefficient of 2 to ( \text{CO} ) on the right.
  • Add a coefficient of 3 to ( \text{C} ) on the left.
  • Balanced: 1 Silicon, 2 Oxygen, 3 Carbon._

Example 7: Complex Equation with Parentheses

• Equation: ( \text{FeCl}_3 + \text{NaOH} \rightarrow \text{Fe(OH)}_3 + \text{NaCl} )
• Atoms Count:
  • Left: 1 Iron, 3 Chlorine, 1 Sodium, 1 Oxygen, 1 Hydrogen
  • Right: 1 Iron, 3 Oxygen, 3 Hydrogen, 1 Sodium, 1 Chlorine
• Balancing:
  • Balance Oxygen and Hydrogen by changing coefficients of ( \text{NaOH} ) and ( \text{NaCl} ).
  • Adjust coefficients as needed to ensure all sides balance.

Conclusion

• As equations get more complex, balancing requires multiple steps and careful manipulation of coefficients.
• Always leave elements that appear alone until the end for easier adjustments.