Ionic Equations

• Ionic Equations


  Equations that show the reactions of ions in water
• Why do we learn ionic equations?

  • Essential for the topic on Electrolysis
  • Helps to identify precipitation reactions
• Ionic equation


  1. Shows the reactions of ions in water

  2. Written in terms of ions
• What happens when an ionic compound dissolves in water?

  1. The ionic compound dissociates

  2. The ions of the compound separate from each other and enter the water
• Dissociation of ionic compounds

  • NaCl (aq) → Na+ (aq) + Cl- (aq)

  CaO (aq) → Ca2+ (aq) + O2- (aq)

  K2SO4 (aq) → 2K+ (aq) + SO42- (aq)

  BaSO4 (s) → No dissociation occurs
• Covalent compounds


  Can dissolve in water to form ions, e.g. acids dissociate to produce hydrogen ions
• Chemical Equation to Ionic Equation

  Rewrite the chemical equation in terms of ions for substances that dissolve in water

  2. Cancel out the spectator ions

  3. Write the ionic equation
• Converting Chemical Equation to Ionic Equation

  • HCl (aq) + NaOH (aq) → NaCl (aq) + H2O (l)

  Pb(NO3)2 (aq) + 2KI (aq) → PbI2 (s) + 2KNO3 (aq)
• Spectator ions


  Ions that appear on both sides of the ionic equation and do not take part in the reaction
• Steps to write ionic equation

  Rewrite the balanced chemical equation in terms of ions for substances that dissolve in water

  2. Cancel out the spectator ions

  3. Write the ionic equation
• Converting Chemical Equation to Ionic Equation

  • Fe (s) + CuSO4 (aq) → FeSO4 (aq) + Cu (s)
• In order to write an ionic equation, a balanced chemical equation is needed