Classifying Chemical Reactions Objectives: 1. Name 4 general types of chemical reactions. 2. Describe each of the four types of chemical reactions. Key Terms: direct combination reaction decomposition reaction single-replacement reaction double- replacement reaction

Direct combination reaction: All reactants combine into the product. – A + B  AB Also called a synthesis reaction No matter how many reactants are present there is only one product Example: C + CO2  2CO or Na + Cl  NaCl

Decomposition reaction A single reactant breaks down into multiple products. – AB  A + B Is the reverse of the direct combination reaction. – Example: 2H 2 O  2H 2 + O 2

Single-replacement reaction The reactants and products both consist of an element and a compound. – AB + C  AC + B Generally occurs in ionic compounds Most occur as a result of being dissolved in water Replacement is based on the chemical activity of the metals. – The stronger reducing agent replaces the metal with the lower reactivity – May also occur with halogens (reactivity decreases as you go down the column) Br 2 + 2NaI g 2NaBr + I 2 – Example: Fe + CuSO 4  Cu + FeSO 4

Double-replacement reaction Atoms and ions from 2 different compounds replace each other. – AB + CD  AD + CB Most occur as a result of being dissolved in water Indicators that a double replacement reaction has taken place: – precipitation - solid separates in solution – effervescence - gas bubbles form – at least one of the products is a molecular compound Example: CaBr 2 + 2AgNO 3  Ca(NO 3 ) 2 + 2AgBr

Combustion Reaction Combustion Reaction: A reaction where at least one substance combines with oxygen to produce light and heat (both forms of energy). burning of hydrocarbons (substances containing H & C) produce CO 2 & H 2 0 – 2C 8 H O 2  16CO H 2 O + light + heat Other combustion reactions – 2Mg + O 2  2MgO – S + O 2  SO 2