Chapter 24 Lesson 3 Classifying Chemical Reactions

Types of Reactions Chemists have defined five main categories combustion synthesis decomposition single displacement double displacement

Combustion Reactions Combustion reaction. occurs when a substance reacts with oxygen to produce energy in the form of heat and light. also produce one or more products that contain the elements in the reactants

C x H y +O 2  CO 2 +H 2 O Combustion CH 4 + 2O 2  CO 2 + 2H 2 O The burning of a substance in O 2 to produce heat Hydrocarbons (C x H y ) always form CO 2 and H 2 O

Synthesis the combination of 2 or more substances to form a compound only one product forms A + B  AB 2P + 3Br 2  2PBr 3

Decomposition Reactions A decomposition reaction reverse of a synthesis decomposition reaction occurs when one substance breaks down, or decomposes, into two or more substances most require the use of heat, light, or electricity.

Decomposition a compound breaks down into 2 or more simpler substances only one reactant AB  A + BAB  A + B 2H 2 O 2  2H 2 O + O 2

Single Replacement one element replaces another in a compound metal replaces metal (+) nonmetal replaces nonmetal (-) A + BC  AC + B Zn + 2HCl  ZnCl 2 + H 2

The Activity Series Predict which metal will replace another using the diagram lists metals according to how reactive they are A metal replace any less active metal.

Double Replacement ions in two compounds “change partners” cation(+) of one compound combines with anion(-) of the other AB + CD  AD + CB 2KOH + CuSO 4  K 2 SO 4 + Cu(OH) 2

Double Displacement Double displacement reaction takes place if a precipitate, water, or a gas forms when two ionic compounds in solution are combined. Precipitate insoluble compound that comes out of solution during this type of reaction.

Oxidation-Reduction Reactions Gain or loss of electrons characteristic that is common to many chemical reactions Oxidation describes the loss of electrons and the term reduction to describe the gain of electrons.

Oxidation-Reduction Reactions Chemical reactions involving electron transfer often involve oxygen, which is very reactive, pulling electrons from metallic elements. Corrosion of metal is a visible result.

Oxidation-Reduction Reactions Reduced gains an electron or electrons obviously becomes more negative Oxidized the substance that loses an electron or electrons then becomes more positive

Oxidation-Reduction Reactions Reduction electrons that were pulled from one atom were gained by another atom in a chemical reaction Redox Reduction is the partner to oxidation; the two always work as a pair