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Types of Reactions. Chapter 9 Section 3. Synthesis. In a synthesis reaction two or more simple substances combine to form a more complex substance. Decomposition. In a decomposition reaction a more complex substance breaks down into its more simple parts. Single Replacement.
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Types of Reactions Chapter 9 Section 3
Synthesis • In a synthesis reaction two or more simple substances combine to form a more complex substance.
Decomposition • In a decomposition reaction a more complex substance breaks down into its more simple parts.
Single Replacement • In a single replacement reaction a single uncombined element replaces another in a compound. • Two reactants yield two products.
Double Replacement • In a double replacement reaction parts of two compounds switch places to form two new compounds. • Two reactants yield two products.
Combustion • A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. • These reactions are exothermic, meaning they produce heat. • An example of this kind of reaction is the burning of methane:
Acid-base • A special kind of double replacement (displacement ) reactionwhen an acid and base react • H+ ion in the acid reacts with the OH- ion in the base forming water • Generally, the product of this reaction is some ionic salt and water: HA + BOH ---> H2O + BA • Example: the reaction of hydrobromic acid (HBr) with sodium hydroxide: • HBr+ NaOH ---> NaBr + H2O
Controlling Chemical Reactions Chapter 9 - Supplemental Section
Activation Energy • Activation energyis the minimum amount of energy that is required to begin all chemical reactions.
Rates of Chemical Reactions • Chemical reactions do not all occur at the same rate. • How fast a reaction happens depends on how fast the particles of the reactants make contact. • The rate of a reaction is affected by such factors as concentration, surface area, temperature, adding a catalyst, or adding an inhibitor.
Collision Theory • Reactions take place as a result of particles colliding. • Not all collisions cause reaction • particles must have sufficient kinetic energy, and the correct orientation to react.
Concentration • Increasing concentration of reactants increases the rate of reaction. • There are more collisions as there are more particles in closer proximity.
Surface Area • An increase in surface area increases the rate of reaction. • Collisions occur at the surface of particles. Increasing surface area exposes more particles of the reactants. • The larger the particle size the smaller the surface area and the fewer collisions can occur.
Temperature • Increasing the temperature increases reaction rate. • Two reasons: 1. There are more particles with sufficient energy to react (most important) - more successful collisions2. There are more collisions
Catalysts • A catalyst is a material that increases a reaction by lowering the activation energy. • Catalysts help with the reaction, but are not changed in the reaction. They usually just provide a surface for reactants to provide a greater probability of proper orientation. • Example: Enzymes
Inhibitors • Inhibitors decrease the rate of reaction. • Examples: • Wood pulp in nitroglycerine • Plants have natural inhibitors to prevent germination until the right conditions are present.
