Chemical Equations and Balancing

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Chemical Equations and Balancing

Definition:

A chemical equation is the symbolic representation of a chemical reaction.
Reactants: Substances initiating the reaction (left side of equation)
Products: Substances formed during the reaction (right side of equation)
Arrow (→) indicates the direction of chemical change

Writing a Chemical Equation:

Step 1: Identify reactants and products, write a word equation

Step 2: Write symbols and formulae, indicate physical states

  • (s) for solid
  • (l) for liquid
  • (g) for gas
  • (aq) for aqueous

Example: Burning of Coal

Word equation: Coal + Oxygen → Carbon Dioxide

Chemical equation: C + O₂ → CO₂

Balancing a Chemical Equation:

Principle: Number of atoms remains the same, only arrangement changes

Example of Balanced Equation: C + O₂ → CO₂

Steps for Balancing:

  • Balance one element at a time using coefficients
  • Start with the lowest coefficient
  • Do not change subscripts in chemical formulas

Example of Balancing:

Unbalanced: CH₄ + O₂ → CO₂ + H₂O

Step 1: CH₄ + O₂ → CO₂ + 2H₂O (balance H atoms)

Step 2: CH₄ + 2O₂ → CO₂ + 2H₂O (balance O atoms)

Final Balanced Equation: CH₄ + 2O₂ → CO₂ + 2H₂O

Ionic Equations:

Definition: Chemical equation where substances dissolved in water are written as individual ions

Steps:

  • Write soluble substances in dissociated form
  • Remove spectator ions (common ions on both sides)

Example:

Reaction: HCl(aq) + NaOH(aq) → NaCl(aq) + H₂O(l)

Dissociated: H⁺(aq) + Cl⁻(aq) + Na⁺(aq) + OH⁻(aq) → Na⁺(aq) + Cl⁻(aq) + H₂O(l)

Net Ionic Equation: H⁺(aq) + OH⁻(aq) → H₂O(l)

Practice Exercises:

  • Writing chemical equations for given reactions
  • Balancing chemical equations
  • Transforming chemical equations into ionic equations

Note: This content covers the basics of chemical equations, balancing, and ionic equations. It provides a foundation for understanding chemical reactions and their symbolic representations.