Net Ionic Equation Examples With Answers

The net ionic equation is a chemical equation that shows only the species that participate in a reaction. It's a simplified way of representing reactions, especially those occurring in aqueous solutions, by eliminating spectator ions that don't undergo any change.

Understanding Ionic Equations

Before diving into net ionic equations, it's essential to understand the broader concept of ionic equations. Ionic equations represent soluble ionic compounds in their dissociated form as ions. Here’s a step-by-step breakdown:

1. Write the Balanced Molecular Equation: This is the regular chemical equation showing all reactants and products as molecules.
2. Write the Complete Ionic Equation: Dissociate all soluble ionic compounds into their respective ions. Keep insoluble compounds, gases, and solids in their molecular form.
3. Identify and Cancel Spectator Ions: Spectator ions are those that appear on both sides of the equation and do not participate in the reaction.
4. Write the Net Ionic Equation: This includes only the ions and compounds that participate in the reaction.

Steps to Write Net Ionic Equations

Here's a detailed guide on how to write net ionic equations effectively:

1. Write the Balanced Molecular Equation
   • Ensure the chemical equation is balanced to satisfy the law of conservation of mass. Each element must have the same number of atoms on both sides of the equation.
2. Write the Complete Ionic Equation
   • Dissociate all aqueous ionic compounds into their ions.
   • For example, NaCl(aq) becomes Na+(aq) + Cl-(aq).
   • Keep solids, liquids, and gases in their molecular form. Do not dissociate them.
3. Identify Spectator Ions
   • Spectator ions are ions that appear unchanged on both the reactant and product sides of the equation.
4. Cancel Spectator Ions
   • Remove the spectator ions from both sides of the complete ionic equation.
5. Write the Net Ionic Equation
   • Write the equation using only the remaining ions and compounds that participate in the reaction.
   • Ensure the equation is balanced both in terms of mass and charge.

Net Ionic Equation Examples with Answers

Let's explore several examples to illustrate the process of writing net ionic equations.

Example 1: Reaction of Silver Nitrate with Sodium Chloride

• Balanced Molecular Equation:

  AgNO3(aq) + NaCl(aq) → AgCl(s) + NaNO3(aq)
  

• Complete Ionic Equation:

  Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) → AgCl(s) + Na+(aq) + NO3-(aq)
  

• Identify Spectator Ions:
  • Na+(aq) and NO3-(aq)
• Cancel Spectator Ions:

  Ag+(aq) + Cl-(aq) → AgCl(s)
  

• Net Ionic Equation:

  Ag+(aq) + Cl-(aq) → AgCl(s)
  

  This equation shows the formation of solid silver chloride from silver and chloride ions.

Example 2: Reaction of Lead(II) Nitrate with Potassium Iodide

• Balanced Molecular Equation:

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

• Complete Ionic Equation:

  Pb2+(aq) + 2NO3-(aq) + 2K+(aq) + 2I-(aq) → PbI2(s) + 2K+(aq) + 2NO3-(aq)
  

• Identify Spectator Ions:
  • 2NO3-(aq) and 2K+(aq)
• Cancel Spectator Ions:

  Pb2+(aq) + 2I-(aq) → PbI2(s)
  

• Net Ionic Equation:

  Pb2+(aq) + 2I-(aq) → PbI2(s)
  

  This equation represents the formation of lead(II) iodide precipitate.

Example 3: Reaction of Sodium Hydroxide with Hydrochloric Acid

• Balanced Molecular Equation:

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

• Complete Ionic Equation:

  Na+(aq) + OH-(aq) + H+(aq) + Cl-(aq) → Na+(aq) + Cl-(aq) + H2O(l)
  

• Identify Spectator Ions:
  • Na+(aq) and Cl-(aq)
• Cancel Spectator Ions:

  H+(aq) + OH-(aq) → H2O(l)
  

• Net Ionic Equation:

  H+(aq) + OH-(aq) → H2O(l)
  

  This is the net ionic equation for any strong acid-strong base neutralization reaction, showing the formation of water.

Example 4: Reaction of Copper(II) Chloride with Sodium Hydroxide

• Balanced Molecular Equation:

  CuCl2(aq) + 2NaOH(aq) → Cu(OH)2(s) + 2NaCl(aq)
  

• Complete Ionic Equation:

  Cu2+(aq) + 2Cl-(aq) + 2Na+(aq) + 2OH-(aq) → Cu(OH)2(s) + 2Na+(aq) + 2Cl-(aq)
  

• Identify Spectator Ions:
  • 2Na+(aq) and 2Cl-(aq)
• Cancel Spectator Ions:

  Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)
  

• Net Ionic Equation:

  Cu2+(aq) + 2OH-(aq) → Cu(OH)2(s)
  

  The net ionic equation shows the precipitation of copper(II) hydroxide.

Example 5: Reaction of Barium Chloride with Sodium Sulfate

• Balanced Molecular Equation:

  BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)
  

• Complete Ionic Equation:

  Ba2+(aq) + 2Cl-(aq) + 2Na+(aq) + SO42-(aq) → BaSO4(s) + 2Na+(aq) + 2Cl-(aq)
  

• Identify Spectator Ions:
  • 2Na+(aq) and 2Cl-(aq)
• Cancel Spectator Ions:

  Ba2+(aq) + SO42-(aq) → BaSO4(s)
  

• Net Ionic Equation:

  Ba2+(aq) + SO42-(aq) → BaSO4(s)
  

  This reaction shows the formation of barium sulfate precipitate.

Example 6: Reaction of Zinc with Hydrochloric Acid

• Balanced Molecular Equation:

  Zn(s) + 2HCl(aq) → ZnCl2(aq) + H2(g)
  

• Complete Ionic Equation:

  Zn(s) + 2H+(aq) + 2Cl-(aq) → Zn2+(aq) + 2Cl-(aq) + H2(g)
  

• Identify Spectator Ions:
  • 2Cl-(aq)
• Cancel Spectator Ions:

  Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)
  

• Net Ionic Equation:

  Zn(s) + 2H+(aq) → Zn2+(aq) + H2(g)
  

  The net ionic equation shows the reaction of zinc metal with hydrogen ions to form zinc ions and hydrogen gas.

Example 7: Reaction of Calcium Carbonate with Hydrochloric Acid

• Balanced Molecular Equation:

  CaCO3(s) + 2HCl(aq) → CaCl2(aq) + H2O(l) + CO2(g)
  

• Complete Ionic Equation:

  CaCO3(s) + 2H+(aq) + 2Cl-(aq) → Ca2+(aq) + 2Cl-(aq) + H2O(l) + CO2(g)
  

• Identify Spectator Ions:
  • 2Cl-(aq)
• Cancel Spectator Ions:

  CaCO3(s) + 2H+(aq) → Ca2+(aq) + H2O(l) + CO2(g)
  

• Net Ionic Equation:

  CaCO3(s) + 2H+(aq) → Ca2+(aq) + H2O(l) + CO2(g)
  

  This equation represents the reaction of calcium carbonate with acid, producing calcium ions, water, and carbon dioxide gas.

Example 8: Reaction of Ammonia with Nitric Acid

• Balanced Molecular Equation:

  NH3(aq) + HNO3(aq) → NH4NO3(aq)
  

• Complete Ionic Equation:

  NH3(aq) + H+(aq) + NO3-(aq) → NH4+(aq) + NO3-(aq)
  

• Identify Spectator Ions:
  • NO3-(aq)
• Cancel Spectator Ions:

  NH3(aq) + H+(aq) → NH4+(aq)
  

• Net Ionic Equation:

  NH3(aq) + H+(aq) → NH4+(aq)
  

  The equation shows the formation of ammonium ions from ammonia and hydrogen ions.

Example 9: Reaction of Iron(III) Chloride with Sodium Hydroxide

• Balanced Molecular Equation:

  FeCl3(aq) + 3NaOH(aq) → Fe(OH)3(s) + 3NaCl(aq)
  

• Complete Ionic Equation:

  Fe3+(aq) + 3Cl-(aq) + 3Na+(aq) + 3OH-(aq) → Fe(OH)3(s) + 3Na+(aq) + 3Cl-(aq)
  

• Identify Spectator Ions:
  • 3Na+(aq) and 3Cl-(aq)
• Cancel Spectator Ions:

  Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s)
  

• Net Ionic Equation:

  Fe3+(aq) + 3OH-(aq) → Fe(OH)3(s)
  

  The net ionic equation shows the precipitation of iron(III) hydroxide.

Example 10: Reaction of Potassium Carbonate with Hydrochloric Acid

• Balanced Molecular Equation:

  K2CO3(aq) + 2HCl(aq) → 2KCl(aq) + H2O(l) + CO2(g)
  

• Complete Ionic Equation:

  2K+(aq) + CO32-(aq) + 2H+(aq) + 2Cl-(aq) → 2K+(aq) + 2Cl-(aq) + H2O(l) + CO2(g)
  

• Identify Spectator Ions:
  • 2K+(aq) and 2Cl-(aq)
• Cancel Spectator Ions:

  CO32-(aq) + 2H+(aq) → H2O(l) + CO2(g)
  

• Net Ionic Equation:

  CO32-(aq) + 2H+(aq) → H2O(l) + CO2(g)
  

  This equation shows the reaction of carbonate ions with acid to produce water and carbon dioxide gas.

Common Mistakes to Avoid

• Not Balancing the Molecular Equation: Always ensure the molecular equation is balanced before proceeding.
• Incorrectly Dissociating Compounds: Only dissociate strong electrolytes (soluble ionic compounds, strong acids, and strong bases). Weak electrolytes and non-electrolytes should not be dissociated.
• Forgetting to Check Solubility Rules: Use solubility rules to determine if a compound is soluble or insoluble. Insoluble compounds do not dissociate into ions.
• Not Balancing the Net Ionic Equation for Charge: Ensure that the total charge is the same on both sides of the equation.
• Including Spectator Ions: Double-check that all spectator ions are removed from the net ionic equation.

Importance of Net Ionic Equations

Net ionic equations are valuable for several reasons:

• Simplicity: They simplify complex chemical reactions, focusing only on the essential changes.
• Clarity: They clearly show which species are actively involved in the reaction.
• Universality: They represent reactions that occur in similar ways regardless of the specific spectator ions present.
• Predictability: They help predict the formation of precipitates, gases, or water in chemical reactions.

Advanced Concepts

• Acid-Base Neutralization Reactions: In all strong acid-strong base reactions, the net ionic equation is always:

  H+(aq) + OH-(aq) → H2O(l)
  

• Gas Formation Reactions: Reactions that produce gases often have characteristic net ionic equations showing the formation of the gas.
• Complex Ion Formation: Some reactions involve the formation of complex ions, which can be represented in net ionic equations.

Conclusion

Mastering net ionic equations is crucial for understanding and predicting chemical reactions in aqueous solutions. By following the step-by-step process and practicing with examples, you can confidently write and interpret these equations. Always remember to balance the molecular equation, correctly dissociate compounds, identify spectator ions, and balance the net ionic equation for both mass and charge. With these skills, you'll be well-equipped to tackle a wide range of chemical reactions.