Why molecular equations can hide the real reaction
A molecular equation is compact, but it can hide which particles are actually changing. In water, many soluble ionic compounds exist as separated ions.
Unit 4: Chemical Reactions
Net Ionic Equations
How can we focus on the particles that actually react in an aqueous solution?
24 min
High School Chemistry / AP Chemistry
5 source chapters
Learning Objectives
- Distinguish molecular, complete ionic, and net ionic equations.
- Identify strong electrolytes that dissociate in water.
- Identify spectator ions.
- Write a net ionic equation by removing unchanged ions.
- Recognize precipitation reactions using solubility rules.
Ions in aqueous solution
Strong soluble ionic compounds are written as ions in complete ionic equations. Solids, liquids, gases, weak acids, and weak bases are not split into ions in this intro workflow.
Spectator ions stay unchanged
When AgNO3(aq) and NaCl(aq) mix, Ag+ and Cl- form solid AgCl. Na+ and NO3- remain dissolved and unchanged, so they are spectators.
Two ionic solutions mix; AgCl precipitates while sodium and nitrate remain dissolved.
From molecular to net ionic
Write soluble strong electrolytes as ions, keep the solid together, then cancel unchanged spectator ions.
AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNO3(aq)
Ag+(aq) + NO3-(aq) + Na+(aq) + Cl-(aq) -> AgCl(s) + Na+(aq) + NO3-(aq)
Ag+(aq) + Cl-(aq) -> AgCl(s)
- 1Start with the molecular equation.
Worked Example
Barium sulfate precipitate
Write the net ionic equation for BaCl2(aq) + Na2SO4(aq) -> BaSO4(s) + 2NaCl(aq).
Quick Check
In AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNO3(aq), which ions are spectators?
Quick Check
Which is the correct net ionic equation for Pb(NO3)2(aq) + 2KI(aq) -> PbI2(s) + 2KNO3(aq)?
Misconception Check
Misconception: Everything with ions in its formula should be split apart.
Correction: Only dissolved strong electrolytes are split in this workflow. Do not split solids, liquids, gases, weak acids, or weak bases.
Key Terms
molecular equation
分子方程式Equation written with neutral formulas for reactants and products.
complete ionic equation
完整离子方程式Equation showing dissolved strong electrolytes as separate ions.
net ionic equation
净离子方程式Equation showing only particles that change during the reaction.
spectator ion
旁观离子Ion that appears unchanged on both sides of an ionic equation.
precipitate
沉淀Insoluble solid formed from ions in solution.
electrolyte
电解质Substance that produces ions in water and conducts electricity.
Summary
- Complete ionic equations show dissolved strong electrolytes as ions.
- Spectator ions appear unchanged on both sides.
- Net ionic equations show only the reacting particles.
- Solids such as precipitates are not split apart.
Practice bridge
Write molecular, complete ionic, and net ionic equations for CaCl2(aq) + Na2CO3(aq).
Circle spectator ions before writing the final net ionic equation.
Related Resources
Marker chapters
- Chemistry 11e By Steven Zumdahl, DeCoste/Chapter 4- Types of Chemical Reactions and Solution Stoichiometry
- Chemistry 14e by Raymond Chang Jason Overby/Chapter 03 - Mass Relationships in Chemical Reactions
- Chemistry 14e by Raymond Chang Jason Overby/Chapter 04 - Reactions in Aqueous Solutions
- Chemistry The Central Science in SI Units 15th Global Edition/Chapter 3- Chemical Reactions and Stoichiometry
- Chemistry The Central Science in SI Units 15th Global Edition/Chapter 4- Reactions in Aqueous Solution
Optional downloads
- net_ionic_equations_student_handout.md
- net_ionic_equations_teacher_guide.md
- net_ionic_equations_qa_report.md
Practice Bridge
Practice this lesson
Move from reading to doing with a short question set, immediate feedback, and explanations.
Practice: not started