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Types of Reactions���

(7.2)

Classifying Reactions •  Reactions are often classified by the

type of reactant or the number of reactants and products

•  Each type of reaction describes a different way in which reactants interact to form products

Synthesis Reactions

• Two or more substances react to produce a single product

• A + B --> AB

•  Can occur between two elements: 2Na (s) + Cl2 (g) --> 2NaCl (s)

•  Can occur between two compounds: CaO (s) + H2O (l) --> Ca(OH)2 (s)

• Can occur between a compound and an element: 2SO2 (g) + O2 (g) --> 2SO3 (g)

Combustion Reactions • When oxygen combines with

another substance and releases energy in the form of heat and light

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•  Example - burning of coal: C (s) + O2 (g) --> CO2 (g)

Decomposition Reactions • When a single compound breaks

down into two or more elements or new compounds

• Often requires an energy source such as heat, light, or electricity to occur

• AB --> A + B •  Example: NH4NO3 (s) --> N2O (g) + 2H2O (g)

Decomposition Reaction Example Single Replacement Reactions

• The atoms of one element replace the atoms of another element in a compound

• A + BX --> AX + B

•  Three types of single replacement reactions

1.  Metal replacing hydrogen: 2Li (s) + 2H2O (l) --> 2LiOH (aq) + H2 (g)

2. Metal replacing another metal:

Cu(s) + 2AgNO3(aq) --> Cu(NO3)2(aq) + 2Ag(s)

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3. Non-metal replacing another non-metal:

F2 (g) + 2NaBr (aq) --> 2NaF (aq) + Br2 (l)

Double Replacement Reactions

•  Involves the exchange of ions between two compounds

• AX + BY --> AY + BX

•  Example: Ca(OH)2(aq) + 2HCl(aq) --> CaCl2(aq) + 2H2O(l)

•  Example: 2NaOH(aq) + CuCl2(aq) --> 2NaCl(aq) + Cu(OH)2(s)

•  The (+) and (-) ions of two compounds

switch places

•  Identify the cations and anions in each compound, then pair up each cation with an anion from the other compound

•  Double replacement reactions form a precipitate (solid), a gas, or water

Double Replacement Reactions