Classifying Chemical Reactions

What is a chemical reaction? A chemical reaction is a process in which one or more substances are converted into new substances with different physical and chemical properties. There are five types of chemical reactions.

Types of chemical reactions 1.) DIRECT COMBINATION REACTIONS (or synthesis reaction) 2.) DECOMPOSITION REACTIONS (or analysis reaction) 3.) SINGLE-REPLACEMENT REACTIONS 4.) DOUBLE-REPLACEMENT REACTIONS 5.) COMBUSTION

1. DIRECT COMBINATION REACTIONS (Synthesis Reactions) In a direct combination reaction, two or more reactants come together to form single product. A + B  AB EXAMPLE: 2 Na + Cl2  2 NaCl

2. DECOMPOSITION REACTIONS (Analysis Reactions) A decomposition reaction is a reaction in which a single compound is broken down into two or more smaller compounds or elements. AB  A + B EXAMPLE: CaCO3  CaO + CO2

3. SINGLE-REPLACEMENT REACTIONS In a single-replacement reaction, an uncombined element displaces an element that is part of a compound. A + BX  AX + B EXAMPLE: Mg + CuSO4  MgSO4 + Cu

4. DOUBLE-REPLACEMENT REACTIONS In a double-replacement reaction, atoms or ions from two different compounds replace each other. AX + BY  AY + BX EXAMPLE: CaCO3 + 2 HCl  CaCl2 + H2CO3

5. CoMbustion Reactions Although the majority of chemical reactions fit into one of the four categories of chemical reactions, there are many reactions that do not. Combustion reactions are reactions in which something is burned. Oxygen gas will be a reactant in this type of reaction. EXAMPLE: 2Mg + O2  2MgO

Classify the following reactions: 1. 2KClO3  2KCl + 3O2 2. HCl + NaOH  NaCl + H2O 3. Mg + 2HCl  MgCl2 + H2 4. 2H2 + O2  2H2O