​Previously

​3.1 Formula Mass and the Mole Concept

3.2 Determining Empirical and Molecular Formulas

3.3 Molarity

3.4 Other Units for Solution Concentrations

​Checking Comprehension

​Chapter Outline

4.1 Writing and Balancing Chemical Equations

4.2 Classifying Chemical Reactions

4.3 Reaction Stoichiometry

4.4 Reaction Yields

4.5 Quantitative Chemical Analysis

​Classifying Chemical Reactions

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• Define three common types of chemical reactions precipitation,

• acid-base, and

• oxidation-reduction

​A precipitation reaction is one in which dissolved substances react to form one (or more) solid products. Many reactions of this type involve the exchange of ions between ionic compounds in aqueous solution and are sometimes referred to as double displacement, double replacement, or metathesis reactions. These

​Acid-Base Reactions

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An acid-base reaction is one in which a hydrogen ion, H⁺, is transferred from one chemical species to another.

​Oxidation-reduction (redox) reactions are those in which one or more elements involved undergo a change in oxidation number.

​Balancing Redox Reactions via the Half-Reaction Method

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1. Write the two half-reactions representing the redox process.

2. Balance all elements except oxygen and hydrogen.

3. Balance oxygen atoms by adding H₂O molecules.

4. Balance hydrogen atoms by adding H⁺ ions.

5. Balance charge by adding electrons.

6. If necessary, multiply each half-reaction’s coefficients by the smallest possible integers to yield equal numbers of electrons in each.

7. Add the balanced half-reactions together and simplify by removing species that appear on both sides of the equation.

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​Balancing Redox Reactions in Acidic Solution

​8. For reactions occurring in basic media (excess hydroxide ions), carry out these additional steps:

1. Add OH⁻ ions to both sides of the equation in numbers equal to the number of H⁺ ions.

2. On the side of the equation containing both H⁺ and OH⁻ ions, combine these ions to yield water molecules.

3. Simplify the equation by removing any redundant water molecules.

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9. Finally, check to see that both the number of atoms and the total charges¹ are balanced.

​Balancing in a basic media (excess hydroxide ions)

​Reaction Stoichiometry

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relationships between the amounts of reactants and products of a chemical reaction

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​Limiting Reactant

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reactant present in an amount lower than required by the reaction stoichiometry, thus limiting the amount of product generated

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​Percent Yield

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​

measure of the efficiency of a reaction, expressed as a percentage of the theoretical yield

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​Titration

​​Gravimetric Analysis:

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quantitative chemical analysis method involving the separation of an analyte from a sample by a physical or chemical process and subsequent mass measurements of the analyte, reaction product, and/or sample