The net ionic equation calculator above takes two reactants dissolved in water, predicts what they form, balances the molecular equation, splits every strong electrolyte into its ions, cancels the ions that appear unchanged on both sides, and shows you what is left. It does this by applying an explicit set of solubility rules rather than by pattern-matching against a list of memorised reactions, and it names which rule decided each species so you can check the reasoning instead of trusting the output.
Arb Digital builds free calculators that show their working. This one matters more than most, because a net ionic equation is easy to produce and easy to produce wrongly: dissociate something that should stay whole, or keep something whole that should have split, and the answer looks perfectly respectable while being completely incorrect. Where this tool cannot reach a defensible answer — an unrecognised formula, a reaction outside its scope, or a combination where nothing actually happens — it says so plainly instead of inventing a plausible equation.
What This Net Ionic Equation Calculator Does
It works in five steps. First it parses each reactant into a cation and an anion, deriving the metal's charge from the formula itself rather than assuming one, so both iron(II) and iron(III) salts are read correctly. Second it swaps the partners to predict the two products, building each formula from the charges so that the result is electrically neutral. Third it balances the molecular equation by searching for the smallest whole-number coefficients that conserve every ion. Fourth it applies the solubility rules to decide which species exist as free ions in solution and which do not. Fifth it cancels the spectators.
The results panel shows all three equations at once. The molecular equation is what you would write on a stock bottle. The complete ionic equation is the honest picture of what is in the beaker. The net ionic equation is the chemistry, with everything that did not participate removed. Underneath, the tool lists the specific solubility rules it applied to reach its conclusion.
A boundary worth stating: our chemical equation balancer balances an equation you supply, of any type, and never asks what dissolves. This page does the opposite — it restricts itself to aqueous double-displacement chemistry so that it can reason about dissociation and precipitation, which balancing alone cannot do.
How to Use It
- Type two reactants separated by a plus sign. Use ordinary formulas with brackets where they belong, such as Pb(NO3)2 or (NH4)2SO4.
- Read the reaction type first. Precipitation, neutralisation, gas-forming and no-reaction are all distinct outcomes with different net ionic equations.
- Check the rules line. It names which solubility rule classified each product, which is the part a marker will want to see.
- Compare the complete ionic and net ionic forms to see exactly which ions were cancelled and why.
- Treat "no reaction" as a real answer. If both products are soluble and nothing molecular forms, there is genuinely no net ionic equation to write.
How the Net Ionic Equation Is Derived
Start with the default example. Silver nitrate and sodium chloride are both soluble, so both exist in water as free ions. Swapping partners gives silver chloride and sodium nitrate. Sodium nitrate is soluble, but silver chloride is not, so it drops out as a solid. The balanced molecular equation is AgNO3 + NaCl → AgCl + NaNO3.
Writing every strong electrolyte as ions gives the complete ionic equation: Ag⁺ + NO₃⁻ + Na⁺ + Cl⁻ → AgCl(s) + Na⁺ + NO₃⁻. The silver chloride stays whole because it is not dissolved and therefore is not present as free ions. Sodium and nitrate appear identically on both sides, unchanged in charge and in count, so they cancel. What remains is Ag⁺(aq) + Cl⁻(aq) → AgCl(s), and that single line is the entire chemistry of the reaction.
The cancellation is not cosmetic tidying. It is a statement that the sodium and nitrate ions were bystanders: they were dissolved before, they are dissolved after, and nothing about them changed. The same net ionic equation would result from potassium chloride and silver nitrate, or from calcium chloride and silver acetate, which is exactly the point — the net ionic equation identifies the reaction rather than the reagents you happened to buy. The Chemistry LibreTexts section on precipitation reactions works through the same three-equation sequence with further examples.
The Solubility Rules This Tool Applies
The rules are applied in order, and an earlier rule takes precedence over a later one where they conflict. This is the same ordering and the same set used in the Chemistry LibreTexts module on solubility rules.
- Rule 1. Salts of lithium, sodium, potassium, rubidium, caesium and ammonium are soluble, without exception.
- Rule 2. Nitrates, acetates, chlorates and perchlorates are soluble.
- Rule 3. Chlorides, bromides and iodides are soluble, except those of silver, lead and mercury(I).
- Rule 4. Silver salts are insoluble, apart from the nitrate and acetate already covered by rule 2.
- Rule 5. Sulfates are soluble, except those of silver, lead, barium, strontium and calcium.
- Rule 6. Hydroxides are insoluble, except those of the group 1 metals and ammonium, with barium and strontium hydroxide soluble and calcium hydroxide only slightly so.
- Rule 7. Sulfides are insoluble, except those of the group 1 and group 2 metals and ammonium.
- Rule 8. Carbonates, chromates, phosphates, oxalates, sulfites and fluorides are insoluble, except those of the group 1 metals and ammonium.
Precedence is what makes rules 1 and 4 compatible. Silver nitrate is soluble because rule 2 fires before rule 4 reaches it. Sodium sulfide is soluble because rule 1 fires before rule 7. Working the rules in the wrong order produces contradictions, which is why a list of memorised exceptions is a much less reliable method than an ordered procedure.
Why "No Reaction" Is a Real Answer
Mix sodium chloride with potassium nitrate in water and nothing happens. The predicted products, sodium nitrate and potassium chloride, are both soluble. All four ions were free before and all four are free afterwards. There is no precipitate, no water formed, no gas released, and consequently no net ionic equation — every species cancels, and an equation with nothing on either side is not an equation.
This tool returns that verdict explicitly rather than producing something that looks like an answer. That matters because a driving force is required: for these reactions it is the removal of ions from solution, whether as an insoluble solid, as a molecular liquid such as water, or as a gas that leaves the beaker. If none of those happens, the mixture is simply a solution of four ions and the reaction has no reason to proceed.
Being told "no reaction" is also the correct answer to a large fraction of exam questions on this topic, and students routinely lose marks by manufacturing an equation instead. The water hardness calculator deals with a practical consequence of the opposite case, where calcium and magnesium ions do precipitate with carbonate.
Strong and Weak Electrolytes, and Why It Decides Everything
Whether a species is written as ions or as a molecule depends entirely on whether it is a strong electrolyte in water. Soluble ionic salts are strong electrolytes and are always split. The six common strong acids — hydrochloric, hydrobromic, hydroiodic, nitric, sulfuric and perchloric — are also split, because they ionise essentially completely. Soluble hydroxides are split for the same reason.
Everything else stays whole. Acetic acid is written as CH3COOH, not as ions, because only a small percentage of it ionises at any moment; writing it as ions would misrepresent what is in the flask by a factor of a hundred or more. Hydrofluoric acid, carbonic acid, hydrogen sulfide and phosphoric acid are all weak and stay molecular. Water itself is written as H2O, since its self-ionisation is negligible on this scale. Our pH calculator and pKa and Ka calculator deal with the extent of that partial ionisation directly.
This single distinction changes the answer completely. Hydrochloric acid with sodium hydroxide gives the net ionic equation H⁺ + OH⁻ → H2O, because both reactants are strong. Acetic acid with sodium hydroxide gives CH3COOH + OH⁻ → CH3COO⁻ + H2O, because the acid does not split. Those are different reactions with different enthalpies, and a tool that treated all acids alike would get one of them wrong every time.
Gas-Forming Reactions and Unstable Products
Some predicted products do not survive being made. An acid with a carbonate gives carbonic acid, which decomposes immediately into water and carbon dioxide, so hydrochloric acid with sodium carbonate has the net ionic equation 2H⁺ + CO₃²⁻ → H2O(l) + CO2(g), and the fizzing is the reaction leaving the beaker. Sulfites behave the same way and release sulfur dioxide. Ammonium salts with a strong base give ammonium hydroxide, which is better written as ammonia plus water.
The calculator handles these three cases explicitly, replacing the unstable intermediate with what actually forms. Escaping gas is a driving force in exactly the same way a precipitate is: it removes product from the solution, so the reaction runs to completion rather than settling at an equilibrium. Our ideal gas law calculator is the tool for working out how much gas that is, and the molar ratio calculator handles the stoichiometry once you have the balanced equation.
What This Tool Will Not Do
Being explicit about limits is more useful than pretending to generality. It does not handle redox reactions, including single displacement of one metal by another, because deciding those requires standard potentials rather than solubility rules — our Nernst equation calculator covers that side. It does not handle complex-ion formation, so it will not tell you that excess ammonia redissolves a silver chloride precipitate. It does not handle organic reactions, oxides, or anything where the cation and anion cannot be identified.
It also treats solubility as a yes-or-no property, which is an approximation. Solubility is a continuum described properly by a solubility product, and the rules are a summary of where that continuum crosses a practical threshold. Calcium hydroxide and calcium sulfate genuinely sit near the boundary, which is why the tool offers a dilute setting that keeps borderline species in solution. Anything at very high concentration, or in a non-aqueous solvent, is outside these rules entirely.
Finally, if a formula cannot be parsed into a recognised cation and anion, the tool names the piece it could not identify and stops. An unrecognised formula produces an error message, never a guess.
Arb Digital publishes hundreds of free calculators across chemistry, maths, finance and marketing — no sign-up, no limits. If something you need is missing, tell us and we will look at building it.
Browse All Free Tools Suggest a ToolCommon Mistakes to Avoid
- Splitting the precipitate into ions — an insoluble solid is not dissolved, so it has no free ions and must be written as a formula with the solid state.
- Splitting a weak acid — acetic, hydrofluoric, carbonic and phosphoric acids stay molecular, and only the six strong acids are written as ions.
- Cancelling before balancing — spectator ions cancel only when their counts match on both sides, and the counts are not known until the equation is balanced.
- Dropping the charges — a net ionic equation must balance in charge as well as in atoms, and the charge balance is the quickest check that it is right.
- Inventing a reaction — if both products are soluble and nothing molecular or gaseous forms, "no reaction" is the correct and complete answer.
Related Free Tools From Arb Digital
Balance equations of any type with the chemical equation balancer, work out the amounts involved with the molar ratio calculator and the molar mass calculator, prepare the solutions with the molarity calculator, and handle the analysis with the titration calculator or the percent yield calculator. For acid strength, the pH calculator is the right page. Everything else is in the free online tools hub.
Frequently Asked Questions
It is the equation left after every ion that appears unchanged on both sides has been cancelled. It shows only the species that actually take part, which is why two different pairs of reagents can share the same net ionic equation.
Only strong electrolytes that are dissolved: soluble ionic salts, the six strong acids, and soluble hydroxides. Precipitates, weak acids, water and gases are written as whole formulas because they are not present as free ions.
Ions that are dissolved before the reaction and still dissolved afterwards, unchanged in charge and in number. They appear identically on both sides of the complete ionic equation and cancel out of the net ionic equation.
It means both predicted products are soluble and nothing molecular or gaseous forms, so every ion is a spectator. There is no driving force and no net ionic equation to write, and that is the correct answer.
An ordered set of eight rules covering group 1 and ammonium salts, nitrates and acetates, halides, silver salts, sulfates, hydroxides, sulfides, and carbonates and phosphates. Earlier rules take precedence where two rules conflict.
Because it is a weak acid and only a small fraction of it ionises at any moment. Writing it as ions would misstate what is in the solution, and it gives a different and incorrect net ionic equation.
No. Deciding a redox reaction needs standard electrode potentials rather than solubility rules, so single displacement and other electron-transfer reactions are outside its scope and it reports that rather than guessing.
Because the predicted product, carbonic acid, is unstable and decomposes immediately into water and carbon dioxide. The escaping gas removes product from solution, which drives the reaction to completion.
This calculator is provided for education and general reference. It describes how net ionic equations are derived and is not laboratory, handling or safety guidance; follow the procedures and risk assessments issued by your own institution.
