Combustion Reactions — The Chemistry of Fire

22件の反応

Combustion is a rapid, exothermic reaction between a substance (the fuel) and an oxidant, usually oxygen, producing heat and light. Complete combustion of hydrocarbons yields carbon dioxide and water; incomplete combustion produces carbon monoxide or soot (elemental carbon). Combustion has powered human civilization since the mastery of fire over a million years ago and remains the primary energy source globally, generating approximately 80 percent of the world's energy.

Reaction Mechanism

Combustion proceeds through a radical chain mechanism with three stages: initiation (heat breaks bonds to create free radicals), propagation (radicals react with fuel and oxygen to create more radicals and products), and termination (radicals combine to form stable products). The flame is a self-sustaining reaction zone where these steps occur simultaneously. The fire triangle — fuel, oxygen, and heat — must all be present; removing any one extinguishes the flame.

Everyday Examples

A gas stove burns methane: CH4 + 2O2 -> CO2 + 2H2O, releasing 890 kJ/mol. Automobile engines combust gasoline (octane: 2C8H18 + 25O2 -> 16CO2 + 18H2O). A candle's wax vaporizes and burns in the flame zone. Even our bodies perform slow combustion — cellular respiration oxidizes glucose to produce ATP energy, carbon dioxide, and water.

産業上の重要性

Fossil fuel combustion generates 36 billion tonnes of CO2 annually, making combustion chemistry central to the climate change discussion. Power plants burn coal, natural gas, or oil to generate electricity. Rocket engines use controlled combustion — the Space Shuttle main engines burned hydrogen and oxygen, producing only water vapor as exhaust. Steel production requires coke combustion in blast furnaces reaching 2,300 degrees C.

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Safety Note

Incomplete combustion produces deadly carbon monoxide (CO), an odorless gas that causes roughly 400 deaths per year in the United States alone. Ensure proper ventilation for all combustion processes. Flammable vapor/air mixtures can explode — never use open flames near volatile organic solvents.

Combustion of Benzene

2C₆H₆ + 15O₂ → 12CO₂ + 6H₂O

Benzene burns with a very smoky, sooty flame due to its high carbon-to-hydrogen ratio. The aromatic ring structure makes benzene …

発熱性 · ΔH = -6535.0 kJ

Combustion of Carbon Monoxide

2CO + O₂ → 2CO₂

Carbon monoxide burns in air with a characteristic blue flame to produce carbon dioxide. This reaction completes the oxidation of …

発熱性 · ΔH = -566.0 kJ

Combustion of Ethane

2C₂H₆ + 7O₂ → 4CO₂ + 6H₂O

Ethane burns in oxygen to produce carbon dioxide and water. Ethane is the second most abundant component of natural gas …

発熱性 · ΔH = -3120.0 kJ

Combustion of Ethylene

C₂H₄ + 3O₂ → 2CO₂ + 2H₂O

Ethylene burns in air with a luminous flame to form carbon dioxide and water. While ethylene can be burned as …

発熱性 · ΔH = -1411.0 kJ

Combustion of Glycerol

2C₃H₈O₃ + 7O₂ → 6CO₂ + 8H₂O

Glycerol (glycerin) burns in oxygen to produce carbon dioxide and water. As a byproduct of biodiesel production, excess glycerol is …

発熱性 · ΔH = -3432.0 kJ

Combustion of Methanol

2CH₃OH + 3O₂ → 2CO₂ + 4H₂O

Methanol burns in air with a nearly invisible pale blue flame, making methanol fires extremely dangerous because they are hard …

発熱性 · ΔH = -1452.0 kJ

Combustion of Propane

C₃H₈ + 5O₂ → 3CO₂ + 4H₂O

Propane combusts in oxygen to produce carbon dioxide and water. Propane is a widely used fuel gas stored as a …

発熱性 · ΔH = -2220.0 kJ

Combustion of Ethanol

C₂H₅OH + 3O₂ → 2CO₂ + 3H₂O

Ethanol burns in oxygen to produce carbon dioxide and water. Ethanol burns with a nearly invisible blue flame. As a …

発熱性 · ΔH = -1367.0 kJ

Combustion of Phenol

2C₆H₅OH + 14O₂ → 12CO₂ + 6H₂O

Phenol burns in air with a very sooty flame due to its aromatic ring structure and high carbon content. Complete …

発熱性 · ΔH = -6108.0 kJ

Combustion of Naphthalene

C₁₀H₈ + 12O₂ → 10CO₂ + 4H₂O

Naphthalene burns with a very smoky, luminous flame characteristic of polycyclic aromatic hydrocarbons. Its high carbon content results in significant …

発熱性 · ΔH = -5157.0 kJ

Combustion of Acetylene

2C₂H₂ + 5O₂ → 4CO₂ + 2H₂O

Acetylene burns in oxygen with an intensely hot flame reaching 3300 C, the hottest of any common fuel-oxygen combination. The …

発熱性 · ΔH = -2600.0 kJ

Combustion of Methane

CH₄ + 2O₂ → CO₂ + 2H₂O

Methane burns in oxygen to produce carbon dioxide and water. This is the primary reaction in natural gas combustion, releasing …

発熱性 · ΔH = -890.4 kJ

Combustion of Butane

2C₄H₁₀ + 13O₂ → 8CO₂ + 10H₂O

Butane burns in oxygen to produce carbon dioxide and water. Butane is the primary fuel in disposable cigarette lighters and …

発熱性 · ΔH = -5754.0 kJ

Combustion of Octane (Gasoline)

2C₈H₁₈ + 25O₂ → 16CO₂ + 18H₂O

Octane, a major component of gasoline, burns in oxygen to produce carbon dioxide and water. This reaction powers internal combustion …

発熱性 · ΔH = -10942.0 kJ

Combustion of Hydrogen Gas

2H₂ + O₂ → 2H₂O

Hydrogen gas burns in oxygen to produce water with no carbon-containing products. This makes hydrogen the ultimate clean fuel. The …

発熱性 · ΔH = -571.6 kJ

Combustion of Cyclohexane

C₆H₁₂ + 9O₂ → 6CO₂ + 6H₂O

Cyclohexane burns in oxygen to produce carbon dioxide and water. As a cycloalkane, cyclohexane has slightly different combustion characteristics than …

発熱性 · ΔH = -3920.0 kJ

Combustion of Hexane

2C₆H₁₄ + 19O₂ → 12CO₂ + 14H₂O

Hexane burns in oxygen to produce carbon dioxide and water. Hexane is a highly flammable alkane commonly used as a …

発熱性 · ΔH = -8386.0 kJ

Combustion of Isopropanol

2C₃H₇OH + 9O₂ → 6CO₂ + 8H₂O

Isopropanol (rubbing alcohol) burns in air with a yellow flame to produce carbon dioxide and water. Isopropanol is very flammable …

発熱性 · ΔH = -4008.0 kJ

Combustion of Sucrose

C₁₂H₂₂O₁₁ + 12O₂ → 12CO₂ + 11H₂O

Sucrose (table sugar) burns in oxygen to produce carbon dioxide and water. When ignited directly, sugar burns slowly. However, when …

発熱性 · ΔH = -5644.0 kJ

Incomplete Combustion of Methane

2CH₄ + 3O₂ → 2CO + 4H₂O

When methane burns in insufficient oxygen, carbon monoxide forms instead of carbon dioxide. This incomplete combustion is dangerous because CO …

発熱性 · ΔH = -1214.0 kJ

Combustion of Glucose (Cellular Respiration)

C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O

The overall equation for cellular respiration is chemically identical to glucose combustion. In living cells, this reaction occurs through many …

発熱性 · ΔH = -2803.0 kJ

Combustion of Xylene

C₈H₁₀ + 10.5O₂ → 8CO₂ + 5H₂O

Xylene (dimethylbenzene) burns with a smoky yellow flame. Xylene exists as three isomers (ortho, meta, para), all with similar combustion …

発熱性 · ΔH = -4553.0 kJ