GCSE Combined Science (AQA)

622 videos | 38 hours

Balanced Chemical Equations

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Atomic structure and the periodic table A simple model of the atom, symbols, relative atomic mass, electronic charge and isotopes

Balanced Chemical Equations

6:31 Chemical Reactions and Equations
Spec 4.1.1.1 4.3.1.1
Previous Chemical Equations Next Advanced Chemical Equations
  • Importance of balancing chemical equations
  • Conservation of mass principle: no atoms lost or created
  • Balanced equation: equal number of atoms of each element on both sides
  • Example: sodium and chlorine reaction
  • Initial unbalanced equation: loss of chlorine atom
  • Balancing by adding multipliers in front of reactants/products
  • Example: adding "2" in front of sodium and sodium chloride
  • Multipliers indicate the number of molecules, not individual atoms
  • Subscripts in equations must not be changed
  • Changing subscripts alters the type of molecule
  • Structured method for balancing equations
  • Example: balancing hydrogen and oxygen to form water
  • Step 1: Count atoms of each element on both sides
  • Step 2: Identify unbalanced elements
  • Step 3: Identify side with fewer atoms
  • Step 4: Use subscripts as multipliers
  • Step 5: Recount atoms after adding multipliers
  • Step 6: Repeat process if still unbalanced
  • Example: balancing hydrogen and oxygen using trial and error
  • Final balanced equation: equal number of hydrogen and oxygen atoms on both sides
  • Practice is essential for mastering balancing equations
  • Other faster methods may exist

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