Reaction Types

Chapter 6.2

Synthesis reactions combine substances

Example C + O2 CO2

OO C + O O C

OO COO C OO C OO C OO

C OO

C OO

CO

O

C OO

C O

O C O

O C OO C

OO C OO C

General: A + B AB

SynthesisExample: NaCl Na + Cl

General: A + B AB

Decomposition reactions break substances apartExample 2HgO 2 Hg + O2

O Hg

O Hg

Hg

O O Hg

+

General: AB A + B

Decomposition Examples• Digestion (breaking down food

molecules into simpler substances) • Electrolysis of water

– Electrolysis—the process by which an electric current is used to produce a chemical reaction

– 2H20 (with electricity) 2H2 + O2

Electrolysis of Water

In single displacement reactions, elements trade place!

Example: CuCl2 + Zn ZnCl2 + Cu

ZnClCl Cu +

General: AX + B BX + A

ClCl Zn Cu+

In double displacement reactions, ions are exchanged between compounds

Example: MgO + CaS MgS + CaO

General: AX + BY AY + BX

SOMg Ca+

O S

Mg Ca+

Combustion is a reaction involving oxygen, where heat is releasedExample: 2CH4 + 4O2 CO2 + 4H2O

Combustion products depend on the amount of

oxygen present• If not enough oxygen is present, a

combustion reaction may produce the toxic carbon monoxide as a product

• Example: 2CH4 + 3O2 CO + 4H2O

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• It’s good to hear it again though…