Types of Chemical Reactions: Combustion & Corrosion

Combustion• when a fuel reacts quickly with oxygen• produces oxides and energy• important source of fuel is hydrocarbons

Complete Combustion of Hydrocarbons• if lots of oxygen is available, complete combustion

• produces carbon dioxide and water

hydrocarbon + oxygen carbon dioxide + water + energy

CxHy + O2 CO2 + H2O + energy

ExampleComplete combustion of butane (C4H10):

2 C4H10(g) + 13 O2(g) 8 CO2(g) + 10 H2O(g) + energy

Incomplete Combustion of Hydrocarbons• if oxygen supply is limited

• produces carbon monoxide gas, carbon (soot), plus carbon dioxide and water

• orange flames are often present

Example

C4H10(g) + 5 O2(g) 2 CO2(g) + 5 H2O(g) + CO(g) + C(s) + energy

Other Types of Combustion

• other substance react with oxygen • forms oxides

General word equation: element + oxygen oxide + energy

General chemical equation: A + O2 AO + energy

Example: 2Mg(s) + O2(g) 2MgO(s) + energy

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Corrosion• breakdown of a metal, due to a reaction with

chemicals in the environment• common example?

Rust• corrosion of iron• reaction with oxygen and water• electrolytes act as a catalyst• can prevent with paint or plastic coating

Beneficial Corrosion

• Sometimes corrosion of some metals forms a tough protective layer that prevents further corrosion

For example, Aluminum: 4 Al(s) + 3 O2(g) 2 Al2O3(s) + energy