Combination of two or more elements into a single new compound.
Equation recognition: multiple reactants on the left, typically one product on the right.
Example: Reaction of solid carbon and gaseous oxygen to form gaseous carbon dioxide.
Decomposition Reactions
Separation of a single compound into two or more new elements or compounds.
Reverse process of synthesis.
Example: Formation of liquid water and gaseous oxygen from liquid hydrogen peroxide.
Equation recognition: single reactant on the left, more than one product on the right.
Single Displacement Reactions
An element reacts with a compound to form a new compound and a different element.
Example: Reaction of solid zinc and aqueous hydrochloric acid.
Equation recognition: element and compound on one side of the arrow, a different element and compound on the other side.
Combustion Reactions
Burning of an element or compound in air; reaction with oxygen.
Release heat and provide energy.
Example: Reaction of solid sulfur with gaseous oxygen to form gaseous sulfur dioxide.
Hydrocarbons (molecules containing only carbon and hydrogen) often appear as reactants.
Products of hydrocarbon combustion: carbon dioxide and water.
Example: Reaction of gaseous methane with gaseous oxygen to form gaseous carbon dioxide and liquid water.
Oxidation-Reduction (Redox) Reactions
All reaction types discussed thus far (synthesis, decomposition, single displacement, combustion) are redox reactions.
Involve a change in oxidation state, with one component being oxidized and one being reduced.
Double Displacement Reactions
Reactions that do not involve changes in oxidation state.
Ions between two reacting compounds simply rearrange.
Two ionic compounds react, with the cation of the first compound combining with the anion of the second, and vice versa.
Ion charges do not change.
Ratio of ions must add up to a neutral formula unit.
Precipitation Reactions
A type of double displacement reaction.
Driving force: formation of an insoluble product (precipitate).
Two soluble ionic compounds in solution exchange ions to form an insoluble ionic compound.
Example: Aqueous barium chloride reacts with aqueous sodium sulfate to form solid barium sulfate and aqueous sodium chloride.
Acid-Base Neutralization Reactions
A type of double displacement reaction.
Driving force: formation of a water molecule.
Strong acid: soluble ionic compound with a hydrogen cation.
Strong base: soluble ionic compound with a hydroxide anion.
Hydrogen and hydroxide combine to form water.
Remaining cation and anion combine to produce another ionic compound.
Example: Aqueous hydrochloric acid reacts with aqueous sodium hydroxide to form liquid water and aqueous sodium chloride.
Reaction Examples
Gaseous hydrogen and gaseous oxygen react to produce liquid water - both synthesis and combustion.
Solid calcium carbonate is heated to produce solid calcium oxide and gaseous carbon dioxide - decomposition reaction.
Gaseous chlorine and aqueous potassium bromide react to produce liquid bromine and aqueous potassium chloride - single displacement reaction.
Aqueous hydrobromic acid and aqueous lithium hydroxide react to produce aqueous lithium bromide and liquid water - double displacement (acid-base neutralization).