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Understanding and Balancing Chemical Equations

Apr 14, 2025

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Lecture on Understanding Chemical Equations

Introduction to Chemical Equations

  • Chemical Equations: Used to show what happens in a chemical reaction.
  • Word Equation Example: Methane burns in oxygen producing carbon dioxide and water.
    • Reactants: Methane and oxygen (left side of the equation).
    • Products: Carbon dioxide and water (right side of the equation).
    • Arrow: Indicates the direction of the reaction (reactants to products).

Symbol Equations

  • Instead of word equations, symbol equations use chemical symbols.
    • Example: CH₄ (methane) + O₂ → CO₂ + H₂O.
    • Molecular Representation: Use O₂ (not O) for oxygen as it exists as a diatomic molecule.
    • Similar rule for other diatomic molecules like Cl₂ (chlorine) and N₂ (nitrogen).

Balancing Chemical Equations

  • Requirement: Same number of each type of atom on both sides of the equation.
  • Example:
    • Left: 1 carbon, 4 hydrogens, 2 oxygens.
    • Right: 1 carbon, 2 hydrogens, 3 oxygens.
    • Goal: Balance oxygens and hydrogens.

Balancing Rules

  1. Do Not Change Subscripts: Changing the small numbers alters the substance itself (e.g., O₂ to O₃).
  2. Adjust Coefficients: Change the big numbers in front of molecules.
    • Increase O₂ to 2 molecules (4 oxygen atoms on left).
    • Increase H₂O to 2 molecules (4 hydrogens, 2 oxygens on right).

Example 2: Balancing Sulfuric Acid and Sodium Hydroxide

  • Reaction: Sulfuric acid + sodium hydroxide → sodium sulfate + water.
  • Initial Count:
    • Left: 3 hydrogens, 1 sulfur, 5 oxygens, 1 sodium.
    • Right: 2 hydrogens, 1 sulfur, 5 oxygens, 2 sodiums.
  • Steps to Balance:
    1. Focus on least common elements first (Sulfur and Sodium).
    2. Balance Sodium by adding a 2 before sodium hydroxide.
    3. Adjust hydrogens and oxygens by adding one more water molecule on the right.
  • Final Check: 4 hydrogens, 1 sulfur, 6 oxygens, 2 sodiums on each side.

Conclusion

  • Ensure all equations are balanced by verifying atom counts on both sides.
  • Always double-check your final equation.
  • Practice balancing with different examples for better understanding.

Enjoyed this session on chemical equations! See you in the next lecture.

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