How to Use This Net Ionic Equation Calculator
- Type the molecular equation with an arrow (
->or=) and states. It does not need to be balanced; the calculator balances it first. - States matter. Whether a product is (s) or (aq) decides whether it is a precipitate, so give the state of every compound except sodium, potassium, ammonium, and nitrate compounds and strong acids and bases, which are filled in for you.
- Ions work too. You can type ions directly, such as
Ag+(aq) + Cl-(aq) -> AgCl(s), using the same charge formats as the balancing equations calculator.
How to Write a Net Ionic Equation in Four Steps
- Balance the molecular equation.
- Write the complete ionic equation by splitting every strong electrolyte that is dissolved (aq) into its ions, multiplied by its coefficient.
- Cancel the spectator ions, the ions that appear unchanged on both sides.
- Reduce the coefficients if they share a common factor, then check that atoms and total charge balance.
For lead(II) nitrate and potassium iodide: Pb(NO3)2(aq) + 2 KI(aq) → PbI2(s) + 2 KNO3(aq) becomes Pb2+ + 2 NO3− + 2 K+ + 2 I− → PbI2(s) + 2 K+ + 2 NO3−. K+ and NO3− cancel, leaving Pb2+(aq) + 2 I−(aq) → PbI2(s). The method is worked through by hand in how to write net ionic equations.
Which Substances Are Split Into Ions
| Substance in the equation | Written as | Examples |
|---|---|---|
| Soluble ionic compound (aq) | Ions | NaCl(aq), Ca(NO3)2(aq), CuSO4(aq) |
| Strong acid (aq) | Ions | HCl, HBr, HI, HClO4, HNO3, H2SO4 |
| Strong base (aq) | Ions | NaOH, KOH, Ba(OH)2 (group 1 and 2 hydroxides) |
| Solid or precipitate (s) | Whole formula | AgCl(s), Mg(OH)2(s) |
| Weak acid or weak base | Whole formula | HC2H3O2, HF, NH3 |
| Liquid, gas, or molecular compound | Whole formula | H2O(l), CO2(g), C6H12O6(aq) |
The six strong acids are the ones the AP course lists by name. A weak acid stays together because most of its molecules do not ionize, which is why acetic acid and sodium hydroxide give HC2H3O2(aq) + OH−(aq) → C2H3O2−(aq) + H2O(l) rather than H+ + OH− → H2O. More on telling them apart is in AP Chemistry strong acids and bases and weak acids.
The One Solubility Rule the AP Exam Expects
The AP Chemistry course description states that all sodium, potassium, ammonium, and nitrate salts are soluble in water, and that memorizing other solubility rules will not be assessed. On the exam, the state of any other compound is given, or there is enough information to work it out, such as a Ksp value or a description of a precipitate. That is why the calculator fills in states only for those four groups and asks you for the rest. The longer traditional list is collected in AP Chemistry solubility rules for reference.
Net Ionic Equations for the Four Main Reaction Types
- Precipitation: BaCl2(aq) + Na2SO4(aq) → Ba2+(aq) + SO42−(aq) → BaSO4(s).
- Strong acid and strong base: any combination, such as HCl(aq) + NaOH(aq), gives H+(aq) + OH−(aq) → H2O(l).
- Gas forming: Na2CO3(aq) + 2 HCl(aq) gives CO32−(aq) + 2 H+(aq) → H2O(l) + CO2(g).
- Redox (single replacement): Zn(s) + CuSO4(aq) gives Zn(s) + Cu2+(aq) → Zn2+(aq) + Cu(s), with sulfate as the spectator.
If every ion cancels, as when NaCl(aq) and KNO3(aq) are mixed, there is no net reaction. How to recognize each reaction type is covered in AP Chemistry types of chemical reactions, and longer redox equations in the half-reaction method. Net ionic equations show up in free-response questions every year; to see how your practice scores translate into a 1–5 estimate, use the AP Chem Score Calculator.
Related Resources
- AP Chem Score Calculator
- All AP Chemistry Calculators
- How to Write Net Ionic Equations
- Balancing Equations Calculator
- AP Chemistry Solubility Rules
- AP Chemistry Types of Chemical Reactions
- Unit 4 Review: Chemical Reactions
Frequently Asked Questions
How do you write a net ionic equation?
Balance the molecular equation, split every soluble ionic compound, strong acid, and strong base marked (aq) into its ions, cancel the ions that appear unchanged on both sides, and reduce the coefficients to the smallest whole numbers. What is left shows only the particles that actually react.
What are spectator ions?
Ions that are present in solution before and after the reaction without changing. In AgNO3(aq) + NaCl(aq) -> AgCl(s) + NaNO3(aq), Na+ and NO3- are spectators, so the net ionic equation is Ag+(aq) + Cl-(aq) -> AgCl(s).
Which compounds are split into ions in a net ionic equation?
Only strong electrolytes dissolved in water: soluble ionic compounds, the strong acids HCl, HBr, HI, HClO4, HNO3, and H2SO4, and strong bases such as the group 1 and group 2 hydroxides. Solids, liquids, gases, weak acids, weak bases, and molecular compounds stay as whole formulas.
Do I need to memorize solubility rules for AP Chemistry?
Only one: all sodium, potassium, ammonium, and nitrate salts are soluble in water. The AP course description says other solubility rules will not be assessed from memory, so exam questions give you the states or the information needed to decide.
What does it mean if there is no net ionic equation?
Every ion cancels as a spectator, so nothing actually reacts. Mixing NaCl(aq) and KNO3(aq), for example, just gives a solution of four kinds of ions with no precipitate, gas, or water formed.
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