Chapter 9 Classifying Chemical Reactions

Vocabulary Definitions:

• Reactant: A substance that undergoes change during a chemical reaction.

• Coefficient: A numerical value placed in front of a chemical formula in an equation to indicate the number of molecules or moles of that substance involved in the reaction.

• Product: A substance that is formed as a result of a chemical reaction.

• Chemical Equation: A symbolic representation of a chemical reaction in which the reactants are shown on the left side and the products on the right side, separated by an arrow.

• Synthesis Reaction: A type of chemical reaction in which two or more reactants combine to form a single product.

• Precipitate: A solid that forms and settles out of a liquid mixture during a chemical reaction.

• Replacement Reaction: A chemical reaction in which one element replaces another in a compound, or in which two elements in different compounds trade places.

• Decomposition Reaction: A reaction in which one compound breaks down into two or more simpler substances.

• Solute: A substance that is dissolved in a solution.

• Solvent: The component of a solution that is present in the largest amount and dissolves the solute.

• Spectator Ion: An ion that exists in the same form on both the reactant and product sides of a chemical equation and does not participate in the reaction.

• Complete Ionic Equation: An equation that shows all of the ions present in a reaction as they are in solution.

• Aqueous Solution: A solution in which water is the solvent.

• Combustion Reaction: A chemical reaction that occurs when a substance combines with oxygen, producing heat and light, typically involving the reaction of a hydrocarbon with oxygen.

Questions and Answers:

1. What are the types of chemical equations?

   • The main types of chemical equations include synthesis reactions, decomposition reactions, single replacement reactions, double replacement reactions, and combustion reactions.

2. What is the difference between a skeleton equation and a chemical equation?

   • A skeleton equation is a representation of the compounds involved in a reaction using their chemical formulas, without coefficients to indicate the relative amounts. A chemical equation includes coefficients that balance the number of atoms on both sides of the equation, indicating the actual quantities involved in the reaction.

3. Why do we use symbols in chemical equations?

   • Symbols in chemical equations represent the elements and compounds involved in a reaction. They provide a concise and universal way to convey information about chemical reactions and help in understanding the stoichiometry and conservation of mass.

4. What results are attributable to each type of chemical reaction?

   • Synthesis reactions result in a single product, decomposition reactions yield simpler substances, single replacement reactions produce one new compound and one element, double replacement reactions result in the exchange of ions between compounds, and combustion reactions typically produce carbon dioxide and water from hydrocarbons.

5. How do dissolved substances exist in aqueous solutions?

   • In aqueous solutions, dissolved substances break apart into ions or molecules and disperse uniformly throughout the water, allowing them to interact with other ions or molecules in the solution.

6. What kinds of byproducts can chemical reactions produce?

   • Chemical reactions can produce a variety of byproducts including gases (e.g., carbon dioxide, oxygen), solids (e.g., precipitates), and other compounds depending on the reactants and conditions of the reaction.

Types of Chemical Equations:

1. Synthesis Reaction: A chemical reaction where two or more reactants combine to form a single product. Example: A + B → AB.

2. Decomposition Reaction: A type of reaction in which a single compound breaks down into two or more simpler substances. Example: AB → A + B.

3. Single Replacement Reaction: A chemical reaction where one element replaces another element in a compound. Example: A + BC → AC + B.

4. Double Replacement Reaction: A reaction where the ions of two compounds exchange places in an aqueous solution to form two new compounds. Example: AB + CD → AD + CB.

5. Combustion Reaction: A reaction that occurs when a substance combines with oxygen, producing heat and light, typically involving a hydrocarbon reacting with oxygen to yield carbon dioxide and water. Example: C_xH_y + O₂ → CO₂ + H₂O.