Net Ionic Equation Example- Chemistry Solution Demonstrations

What Is a Net Ionic Equation?

A net ionic equation shows only the particles that actually participate in a chemical reaction. Everything else gets cut out. That's the whole point.

When you dissolve two salts in water and they react, you're usually watching ions interact. The complete ionic equation shows every single ion floating around. The net ionic equation strips away the spectators—the ions that don't change—and leaves you with what actually happened.

This matters because it tells you the real chemistry. Different reactions can produce the same net ionic equation. That's useful information.

The Vocabulary You Need First

Before you write a single net ionic equation, you need these terms locked down:

• Spectator ions — ions present in the solution but don't take part in the reaction. They just watch.
• Complete ionic equation — shows every ion in the solution, both reacting and spectator
• Strong electrolyte — a substance that completely dissociates into ions in water (soluble salts, strong acids, strong bases)
• Weak electrolyte — only partially dissociates (weak acids, weak bases, slightly soluble salts)
• Precipitate — an insoluble solid that forms when two solutions mix

Solubility Rules: Your Non-Negotiable Reference

You cannot write net ionic equations without knowing solubility. Period. Here are the basics:

• Soluble: All nitrates, acetates, ammonium salts, alkali metal compounds
• Soluble: Most chlorides, bromides, iodides (except Ag, Pb, Hg)
• Soluble: Most sulfates (except Ba, Pb, Ca, Sr)
• Insoluble: Carbonates, phosphates, chromates (except alkali metals and ammonium)
• Insoluble: Hydroxides (except alkali metals, Ca, Ba, Sr)
• Insoluble: Sulfides (except alkali metals, alkaline earth metals, ammonium)

If you don't know these, memorize them. Keep a reference card handy until they're automatic.

Strong vs Weak Electrolytes: Don't Mix These Up

This trips people up constantly.

Strong electrolytes dissociate completely. Write them as separate ions in the complete ionic equation. This includes:

• Strong acids: HCl, HBr, HI, HNO₃, H₂SO₄, HClO₄
• Strong bases: NaOH, KOH, LiOH, Ca(OH)₂, Ba(OH)₂
• Soluble salts: NaCl, KNO₃, MgSO₄, NH₄Cl

Weak electrolytes don't fully dissociate. You write them as intact molecules. This includes:

• Weak acids: CH₃COOH (acetic acid), HF, H₂CO₃
• Weak bases: NH₃ (ammonia), most hydroxides
• Insoluble salts: AgCl, PbI₂, BaSO₄

The Step-by-Step Process

Here's how to actually do this:

Step 1: Write the Balanced Molecular Equation

Start with what you know. Two reactants, one product that precipitates (or a gas, or water).

Step 2: Break Soluble Compounds into Ions

Identify which compounds are strong electrolytes. Dissociate them completely. Leave weak electrolytes as whole units.

Step 3: Write the Complete Ionic Equation

Show every ion. Include state symbols—(aq) for dissolved, (s) for solid, (g) for gas, (l) for liquid.

Step 4: Cancel the Spectator Ions

Find ions that appear on both sides unchanged. Cross them out. What's left is your net ionic equation.

Step 5: Verify

Check that charges balance. Check that atoms balance. If they don't, something went wrong.

Example 1: Silver Nitrate + Sodium Chloride

This is the classic example. Simple, straightforward, and you'll see it in every textbook.

Reactants: AgNO₃(aq) + NaCl(aq)

Step 1 — Molecular equation:

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

Step 2 — Complete ionic equation:

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

Step 3 — Cancel spectators:

Na⁺ and NO₃⁻ appear on both sides. They're doing nothing. Remove them.

Step 4 — Net ionic equation:

Ag⁺(aq) + Cl⁻(aq) → AgCl(s)

That's it. Silver ions and chloride ions form solid silver chloride. Everything else is window dressing.

Example 2: Lead(II) Nitrate + Potassium Iodide

Yellow lead(II) iodide is satisfying to watch precipitate. Here's how you get there.

Step 1 — Molecular equation:

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

Step 2 — Complete ionic equation:

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

Step 3 — Cancel spectators:

K⁺ and NO₃⁻ cancel out again. They never participate.

Step 4 — Net ionic equation:

Pb²⁺(aq) + 2I⁻(aq) → PbI₂(s)

Notice the coefficients. Lead needs two iodides. You can't cancel unless the stoichiometry is correct.

Example 3: Sodium Hydroxide + Hydrochloric Acid

This is a neutralization reaction. It produces water.

Step 1 — Molecular equation:

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

Step 2 — Complete ionic equation:

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

Step 3 — Cancel spectators:

Na⁺ and Cl⁻ cancel. They're watching.

Step 4 — Net ionic equation:

H⁺(aq) + OH⁻(aq) → H₂O(l)

This is the net ionic equation for any strong acid reacting with any strong base. Same result. That's the power of this—you can predict reactions.

Example 4: Barium Chloride + Sodium Sulfate

This one gives you barium sulfate, which is insoluble and used in medical imaging.

Step 1 — Molecular equation:

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

Step 2 — Complete ionic equation:

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

Step 3 — Cancel spectators:

Na⁺ and Cl⁻ cancel.

Step 4 — Net ionic equation:

Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

Common Mistakes That Ruin Your Answers

These errors show up constantly:

• Forgetting to balance charges. The net ionic equation must have equal total charge on both sides. Check this every time.
• Dissociating weak electrolytes. Acetic acid stays CH₃COOH. Ammonia stays NH₃. Don't break them apart.
• Not knowing solubility rules. If you can't predict the precipitate, you can't write the equation.
• Canceling incorrectly. You can only cancel ions that appear in identical form on both sides. Pb²⁺ on one side and Pb²⁺ on the other? Cancel. Different coefficients? Adjust first.
• Leaving state symbols out. (aq) vs (s) matters. It tells you what's dissolved and what's solid.
• Forgetting coefficients in the net equation. If you need 2Cl⁻ to balance, you write 2Cl⁻.

Writing Net Ionic Equations for Gas-Forming Reactions

Some reactions don't produce precipitates—they produce gases. The process is identical.

Example: Sodium Carbonate + Hydrochloric Acid

Na₂CO₃(aq) + 2HCl(aq) → 2NaCl(aq) + H₂O(l) + CO₂(g)

Complete ionic:

2Na⁺(aq) + CO₃²⁻(aq) + 2H⁺(aq) + 2Cl⁻(aq) → 2Na⁺(aq) + 2Cl⁻(aq) + H₂O(l) + CO₂(g)

Net ionic:

CO₃²⁻(aq) + 2H⁺(aq) → H₂O(l) + CO₂(g)

Same process. Cancel what doesn't change. Done.

Weak Acid + Strong Base: Watch the Electrolytes

When a weak acid reacts, you can't write it as ions. Here's acetic acid + sodium hydroxide:

CH₃COOH(aq) + NaOH(aq) → CH₃COONa(aq) + H₂O(l)

Complete ionic:

CH₃COOH(aq) + Na⁺(aq) + OH⁻(aq) → Na⁺(aq) + CH₃COO⁻(aq) + H₂O(l)

Net ionic:

CH₃COOH(aq) + OH⁻(aq) → CH₃COO⁻(aq) + H₂O(l)

Notice: acetic acid stays whole. Only the strong base dissociates. This is where people fail—they write H⁺ + OH⁻ → H₂O for weak acids. That's wrong.

Comparison: Molecular, Complete Ionic, and Net Ionic

Practice Problems to Work Through

Try these before checking answers:

1. Mixing iron(III) chloride with sodium hydroxide produces Fe(OH)₃. Write the net ionic equation.
2. Sulfuric acid reacts with barium hydroxide. Write the net ionic equation.
3. ammonium sulfide mixed with copper(II) sulfate. Write the net ionic equation.

Answers:

1. Fe³⁺(aq) + 3OH⁻(aq) → Fe(OH)₃(s)

2. Ba²⁺(aq) + 2OH⁻(aq) + 2H⁺(aq) + SO₄²⁻(aq) → BaSO₄(s) + 2H₂O(l)

Net: Ba²⁺(aq) + SO₄²⁻(aq) → BaSO₄(s)

3. Cu²⁺(aq) + S²⁻(aq) → CuS(s)

How to Get Faster at This

Speed comes from two things: knowing your solubility rules cold and practicing until the cancellation step is automatic.

Start with soluble + soluble reactions that form an insoluble product. Write the molecular equation, dissociate everything that's strong, cancel, verify. Do 20 of these and you'll have it down.

Don't try to skip steps in your head. Write it out. Every time. Until the process is mechanical.

The net ionic equation isn't complicated. It's systematic. Follow the steps, check your work, and the correct answer appears every time.