# Chemical Equations Library - Searchable Balanced Equations with Conditions, Observations and Ionic Equations

> Free searchable library of 386 balanced chemical equations from school to general chemistry, with conditions, observations, ionic equations and flash cards.

- URL: https://qilingtools.com/en/chemistry/reaction-library
- Category: Chemistry Tools (https://qilingtools.com/en/chemistry)
- Tags: [Chemistry](https://qilingtools.com/en/tags/chemistry)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

A correct chemical equation needs the right formulas, coefficients, conditions and state marks. Iron wire burning in oxygen is 3Fe + 2O₂ → Fe₃O₄ (black magnetite, not Fe₂O₃): it burns vigorously, throws out sparks and leaves a black solid. Iron in dilute hydrochloric acid gives only iron(II): Fe + 2HCl → FeCl₂ + H₂↑, net ionic Fe + 2H⁺ → Fe²⁺ + H₂↑. This library holds 386 equations — 91 from the Chinese middle-school curriculum (oxygen and combustion, preparing O₂, H₂ and CO₂, metals with acids and salts, acid–base–salt reactions, carbon chemistry), 262 from high school (sodium, aluminium, iron, copper, chlorine, sulfur, nitrogen and silicon chemistry, electrolysis and batteries, hydrolysis, and organic substitution, addition, elimination, esterification, hydrolysis, polymerization and oxidation) and 33 general-chemistry reactions such as industrial processes, thermal decompositions, iodometry and dichromate titrations. Every entry shows the conditions above and below the arrow (ignite, Δ, high temperature, electrolysis, catalyst, light, spark, conc. H₂SO₄ at 170 °C…), the reaction types and level, and key reactions add observations, practical notes and the ionic equation. All molecular and ionic equations are automatically checked for atom and charge balance. Search by formula (Fe2O3), English or Chinese name (iron oxide) or observation, tap any substance to list every reaction it appears in, and copy an equation as plain Unicode text or LaTeX (mhchem \ce{}). Flash-card mode hides the products or the coefficients for practice.

## How to use

1. Type a formula, substance name, observation or reaction type, or filter by level, type and element
2. Read the equation, conditions, observation and ionic equation; tap a substance to see every reaction involving it
3. Copy the equation as text or LaTeX, or switch to flash cards to practise predicting products and balancing

## Features

- 386 school and general-chemistry equations, all verified for atom and charge balance
- Conditions shown above and below the arrow: ignite, heat, high temperature, electrolysis, catalyst, light, spark
- Full-text search by formula, English or Chinese name, observation or reaction type
- Filter by level, 20 reaction types (synthesis, decomposition, single and double displacement, redox, substitution, addition, elimination, esterification…) and element
- Observations, practical notes and net ionic equations for key reactions
- Tap any substance to list every reaction that involves it
- Copy as plain Unicode text or LaTeX mhchem
- Flash cards: hide the products or fill in the coefficients, with scoring

## FAQ

### What is the equation for iron burning in oxygen?

3Fe + 2O₂ → Fe₃O₄. Iron wire burns in pure oxygen with a shower of sparks, releasing a lot of heat and forming black iron(II,III) oxide (magnetite), not red Fe₂O₃. A little water or sand is placed in the gas jar so the molten droplets do not crack it. In air iron only glows; rust (Fe₂O₃·xH₂O) forms by slow oxidation in the presence of water.

### How do you write a net ionic equation?

Write the balanced molecular equation, split strong electrolytes that are dissolved (strong acids, strong bases and soluble salts) into ions, keep elements, oxides, gases, precipitates, water and weak acids or bases as formulas, then cancel the spectator ions and check that atoms and charges balance. For example CaCO₃ + 2HCl → CaCl₂ + H₂O + CO₂↑ becomes CaCO₃ + 2H⁺ → Ca²⁺ + H₂O + CO₂↑. The library gives the ionic equation for the reactions where it is usually asked.

### When do you use the ↑ and ↓ symbols?

Mark a gaseous product with ↑ when none of the reactants is a gas, and mark a precipitate with ↓ when the reaction happens in solution and none of the reactants is a solid. If a reactant is already a gas (C + O₂ → CO₂) or a solid (Fe + CuSO₄ → FeSO₄ + Cu), the product is not marked. Conditions such as ignite, heat (Δ), high temperature, electrolysis or a catalyst are written above or below the arrow.

### Is NaAlO₂ or Na[Al(OH)₄] the correct product of aluminium and sodium hydroxide?

Both describe the same solution. Older texts write 2Al + 2NaOH + 2H₂O → 2NaAlO₂ + 3H₂↑ with 'sodium aluminate', while newer texts show the hydrated complex ion actually present: 2Al + 2NaOH + 6H₂O → 2Na[Al(OH)₄] + 3H₂↑. Either is normally accepted as long as you are consistent; the library lists both forms with their ionic equations.

## Related tools

- [Significant Figures Calculator](https://qilingtools.com/en/math/significant-figures): Free online sig fig calculator: count significant figures digit by digit, round to N sig figs or decimals with six rounding modes, and compute by sig fig rules.
- [Chemical Equation Balancer](https://qilingtools.com/en/chemistry/chemical-equation): Balance chemical equations by the algebraic method: smallest whole-number coefficients, brackets, hydrates, ionic charges, electrons, atom and charge checks.
- [Molar Mass Calculator](https://qilingtools.com/en/chemistry/molar-mass): Molar mass of any formula with IUPAC atomic weights: brackets and hydrates, mass percent of each element, grams ↔ moles ↔ particles and solution molarity.
- [Interactive Periodic Table](https://qilingtools.com/en/chemistry/periodic-table): Interactive periodic table of all 118 elements: colour by category, block, electronegativity, atomic mass, phase or melting point; search and click for details.
- [pH Calculator](https://qilingtools.com/en/chemistry/ph): Free pH calculator for strong and weak acids and bases, polyprotic acids, salts and buffers, with an exact charge-balance solution and species plots.
- [Titration Curve](https://qilingtools.com/en/chemistry/titration): Free acid-base titration curve simulator: exact curves for strong, weak and polyprotic acids and bases, equivalence-point pH, the jump and indicator picks.
- [Gas Law Calculator](https://qilingtools.com/en/chemistry/gas-law): Free gas law calculator: solve PV=nRT for any variable, combined gas laws, gas density, Dalton's partial pressures, gas over water and van der Waals Z.
- [Solution & Dilution Calculator](https://qilingtools.com/en/chemistry/solution): Free dilution calculator: solve C1V1=C2V2, convert molarity, % w/w, ppm and molality, mix solutions, plan serial dilutions and dilute stock acids.