TYPES OF CHEMICAL REACTIONS

CLASSIFYING CHEMICAL CHANGES

§The products of a chemical reaction may often be predicted by applying known facts about common reaction types

§Five general types of reactions:§Single displacement§Double displacement§Decomposition§Synthesis§Combustion

SINGLE DISPLACEMENT

§ (aka single replacement)§ One element displaces another element in a compound

§Based on activity series of reactivity §Metal replaces metal (+)§Nonmetal replaces nonmetal (-)

§ General form: § element + compound à element + compound

A + BC ® B + AC

General Types of Single Displacement Reactions:

§Replacement of metal by more active metal§Ex: Al + Fe(NO3)2 à Fe + Al(NO3)3

§Replacement of H in water by a more reactive Group 1 metal§Ex: Na + H2O à NaOH + H2

§Replacement of H in water by more reactive Group 2 or transition metal§Ex: Mg + H2O à MgO + H2

§Replacement of H in an acid by a more reactive metal§Ex: Mg + HCl à MgCl2 + H2

§Replacement of a halogen (nonmetal) by a more reactive halogen§Ex: Cl2 + NaBr à NaCl + Br2

DOUBLE DISPLACEMENT

§ (aka double replacement)§ Ions in two compounds “change partners”§Cation of one compound combines with the anion of the other compound§General form:

§compound + compound à compound + compound

AB + CD ® AD + CB

General types of double displacement reactions:

§Formation of water (acid/base neutralization)§Ex: H2SO4 + NaOH à Na2SO4 + H2O

§Formation of a gas§Ex: CaCO3 + HCl à CaCl2 + H2O + CO2

§Formation of a precipitate (insoluble substance)§Ex: Pb(NO3)2 + NaI à PbI2 + NaNO3

DECOMPOSITION

§A compound breaks down into 2 or more simpler substances§Only one reactant§General form:

§compound à two or more substances

AB ® A + Bone reactant

General types of decomposition reactions:

§Decomposition of binary compounds§Ex: NaCl à Na + Cl2

§Decomposition of metal carbonates to form metal oxides and CO2§Ex: CaCO3 à CaO + CO2

§Decomposition of metal hydroxides to form metal oxides and H2O§Ex: Mg(OH)2 à MgO + H2O

§Decomposition of metal chlorates to form metal chlorides and O2§Ex: KClO3 à KCl + O2

SYNTHESIS

§The combination of 2 or more substances to form a compound§Only one product§General form:

§element or compound + element or compound à compound

A + B ® ABone product

General types of synthesis reactions:

§Oxygen reacts with metals to form metal oxides§Ex: O2 + Mg à MgO

§Two nonmetals react to form a covalent bond§Ex: S + O2 à SO2

§Metals react with nonmetals to form ionic “salts”§Ex: Mg + Cl2 à MgCl2

COMBUSTION

§Contains oxygen (O2)§Usually contains hydrocarbons (H and C molecules) combine with oxygen

to produce a large amount of energy, which produce CO2 + H2O§General form:

§Hydrocarbon + oxygen à carbon dioxide + water

§Ex: The burning of propaneC3H8 + 5O2 à 3CO2 + 4H2O

CxHy + O2 ® CO2 + H2Ohydrocarbon

YOU TRY!

Balance and classify the following chemical reactions:1. __ Na3PO4 + __ KOH à ___ NaOH + __ K3PO4

2. __ P4 + __ O2 à __ P2O3

3. __ NO2 à __ O2 + __ N2

4. __ AgNO3 + __ Cu à __ Cu(NO3)2 + __ Ag

5. __ C3H6O + __ O2 à __ CO2 + __ H2O

1 3 3 1

double displacement1 3 2

synthesis2 2 1

decomposition2 1 1 2

single displacement1 4 3 3

combustion