Types of Chemical Reactions PDF
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James Madison High School
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This document provides a detailed explanation of different types of chemical reactions, including combination, decomposition, single-replacement, double-replacement, and combustion reactions.
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# What Are Chemical Reactions? Chemical reactions are both destructive and creative processes: the bonds among the atoms of the reactants are destroyed in order to create new products. To chemically react, molecules must collide with one another and overcome certain energy barriers. Some types of r...
# What Are Chemical Reactions? Chemical reactions are both destructive and creative processes: the bonds among the atoms of the reactants are destroyed in order to create new products. To chemically react, molecules must collide with one another and overcome certain energy barriers. Some types of reactions are faster than others. Chemical reactions can be classified into five basic types of reaction: ## 1. Combination Reactions Also known as synthesis reactions, these happen when two or more reactants form a single product: A + B → AB Typically, reactions between elements are combination reactions, such as when sodium reacts with chlorine: 2Na(s) + Cl<sub>2</sub>(g) → 2NaCl(s) ## 2. Decomposition Reactions These are the reverse of combination reactions. Put simply, a compound breaks down into its simpler constituent elements or simpler compounds under certain conditions. The simplest type is a binary compound that decomposes into its elements: AB → A + B A good example of this reaction is the decomposition of sodium hydroxide, under heat, into sodium oxide and water: 2NaOH(s) → Na<sub>2</sub>O(s) + H<sub>2</sub>O(g) ## 3. Single-Replacement Reactions These are also known as single-displacement reactions, wherein one element displaces a similar element in a compound. If the element is metallic, it's replaced by a metallic element with a higher reactivity: A + BC → AC + B An example of this type of reaction is the reaction between magnesium and an aqueous solution of copper (II) nitrate: Mg(s) + Cu(NO<sub>3</sub>)<sub>2</sub>(aq) → Mg(NO<sub>3</sub>)<sub>2</sub> + Cu(s) ## 4. Double-Replacement Reactions These reactions only occur between ionic compounds. The positive and negative ions in two compounds exchange places to form new compounds: AB + CD → AD + CB ## 5. Combustion Reactions Combustion reactions can be considered a special form of chemical reaction, which can be either a combination or replacement reaction. The main distinction is that it always involves oxygen. Combustion reactions produce energy in the form of light and heat. In other words, it's the process of **burning**. It could also be explosive in nature, such as in the case of burning the gunpowder inside dynamite: Substance + O<sub>2</sub> → Oxide remains + Other byproducts One of the simplest examples of combustion is the reaction between hydrogen and oxygen in the presence of a spark: 2H<sub>2</sub>(g) + O<sub>2</sub>(g) → 2H<sub>2</sub>O(g) Most combustion reactions occur with hydrocarbons or organic compounds. One simple example of this is the combustion of propane. The complete combustion of hydrocarbons always produces water and carbon dioxide: C<sub>3</sub>H<sub>8</sub>(g) + 5O<sub>2</sub>(g) → 3CO<sub>2</sub>(g) + 4H<sub>2</sub>O(g)
