Notes on Balancing Chemical Equations

Definition of a Balanced Equation

• A balanced equation has the same number of each type of atom on both sides of the equation.
  • This means that the mass and charge are conserved in a chemical reaction.

Balancing Chemical Equations

• To balance a chemical equation, you must ensure that the number of reactant atoms equals the number of product atoms.
• You can adjust coefficients, but not subscripts, to achieve balance.

Example of Balancing

• Review the original equation given:
  • Unbalanced Equation: aA + bB \rightarrow cC + dD
  • Balance by adjusting coefficients (a, b, c, d) without changing the subscripts of compounds.

Reactants and Products

• Reactants: The starting substances in a chemical reaction.
• Products: The substances formed as a result of the chemical reaction.
• Example: In the reaction C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O
  • Reactants: Glucose (C6H{12}O6) and oxygen (O2)
  • Products: Carbon dioxide (CO2) and water (H2O)

Importance of Subscripts

• Subscripts: Represent the number of atoms in a molecule.
  • Example: In H_2O, the subscript 2 indicates there are two hydrogen atoms for every one oxygen atom.
• Changing subscripts alters the substance completely and is NOT allowed in balancing equations.
• You can only change coefficients to balance equations, maintaining the integrity of the chemical identities.

Drawing Molecular Structures

• To visualize molecules when balancing, draw them out:
  • Carbon (C)
  • 3 Carbon atoms: C_3
  • Water molecules represented as 3 H_2O
  • Result of the reaction should also show as: 2H_2O.

Checking Balance

• After balancing, always check that both sides of the equation reflect the same number of each atom.
• For instance, in the equation:
  • Original reaction: C6H{12}O6 + 6O2 \rightarrow 6CO2 + 6H2O
  • Check:
  • Left: 6 Carbon, 12 Hydrogen, 12 Oxygen
  • Right: 6 Carbon, 12 Oxygen + 6 Hydrogen from 6H_2O = 12 Hydrogen
• Thus, it is balanced after confirming that all elements are equal on both sides.