Type reactants, get the balanced products. Exact rules and exact math. When a reaction is outside its rulebook, it tells you instead of guessing.
Tip: to balance a known equation exactly, include an arrow, e.g. Fe + O2 -> Fe2O3. States like (aq) are optional.
Synthesis: element + oxygen, halogens, sulfur or nitrogen; oxides + water; basic oxide + acidic oxide.
Decomposition (heated): carbonates, bicarbonates, hydroxides, chlorates, nitrates, peroxide, ammonium salts, HgO, Ag2O, water electrolysis.
Combustion: any C, H (and O) fuel in excess oxygen, plus H2, C, S, P and metals.
Single replacement: metal + acid, metal + salt, metal + water, halogen + halide, using the standard activity series.
Double replacement: precipitation by full solubility rules, gas formation, and acid + base, carbonate, sulfite, sulfide or oxide.
Named classics: thermite, blast furnace, copper + nitric acid, Haber process, and more.
Plus: an exact balancer for any equation you type with an arrow, and about 200 recognized compound names.