Ion Exchange Reactions: Equations Made Easy
Ion Exchange Reactions: Equations Made Easy
Items in this lesson
Ion Exchange Reactions: Equations Made Easy
What do you already know about ion exchange reactions and writing equations?
Learning Objectives
At the end of the lesson you will: • Understand the conditions for ion exchange reactions. • Know how to write molecular, complete ionic, and net ionic equations. • Accurately determine whether a reaction will occur.
Quick Recap: Electrolytes & Dissociation
Electrolytes are substances that conduct electricity in water by forming ions. Dissociation is the process where substances break into ions when dissolved. Rule: Reactants in ion exchange reactions must be aqueous solutions.
What Are Ion Exchange Reactions?
Ion exchange reactions involve swapping ions between two compounds in solution. General scheme: AB + CD → AD + CB. Key: The total charge must be conserved.
Key Conditions for Reactions
A reaction goes to completion if at least one product is: • An insoluble precipitate (↓) • A gas (↑) • Water (H₂O) If all products are soluble—no reaction occurs.
Examples: Conditions in Action
AgNO₃ + NaCl → AgCl↓ + NaNO₃ AgCl is an insoluble white precipitate.
Na₂CO₃ + HCl → NaCl + CO₂↑ + H₂O Gas (CO₂) forms. OR HCl + NaOH → NaCl + H₂O Water forms.
Formation of Gas / Water
Formation of Precipitate
Solubility Table (Short Version)
Main soluble compounds: • All nitrates (NO₃⁻), all Na⁺, K⁺, NH₄⁺ salts Main insoluble compounds: • Most Ag⁺, Pb²⁺, BaSO₄, CaCO₃ Refer to this summary to predict precipitate formation.
Three Types of Equations: Step-by-Step
Example: CuSO₄(aq) + 2NaOH(aq) → Cu(OH)₂↓ + Na₂SO₄(aq) Step 1: Molecular equation (show all formulas, indicate states) Step 2: Complete ionic equation (strong electrolytes as ions, insoluble/weak/molecules as molecules) Step 3: Net ionic equation (remove spectator ions)
Algorithm for Writing Equations
1. Write reactants and predict products, consulting the solubility table. 2. Indicate states (aq, ↓, ↑, l). 3. Expand strong electrolytes to ions—keep insoluble or molecular products together. 4. Cancel spectator ions to get net ionic equation. 5. Double-check charge and atom balance.
Worked Example: Stepwise Solution
CuSO₄(aq) + 2NaOH(aq) → Cu(OH)₂↓ + Na₂SO₄(aq)
1. Molecular Equation
2. Complete Ionic / 3. Net Ionic
Complete ionic: Cu²⁺(aq) + SO₄²⁻(aq) + 2Na⁺(aq) + 2OH⁻(aq) → Cu(OH)₂↓ + 2Na⁺(aq) + SO₄²⁻(aq) Net ionic: Cu²⁺(aq) + 2OH⁻(aq) → Cu(OH)₂↓
Practice: Test Your Skills
1. Will a reaction occur? NaCl(aq) + AgNO₃(aq) 2. Write the molecular equation for: OH⁻(aq) + H⁺(aq) → H₂O(l) 3. For BaCl₂(aq) + Na₂SO₄(aq), write all three equations.
Self-Check: Key Questions
When a product is a precipitate, gas, or water.
An ion that does not change or participate in forming the main product. Net ionic equations show only the species involved in the actual chemical change.
2. What is a spectator ion? 3. Why use net ionic equations?
1. When does a reaction occur?
Write down 3 things you learned in this lesson.
Write down 2 things you want to know more about.
Ask 1 question about something you haven't quite understood yet.
