General Chemistry Exam 3 Study Notes

Review of Previous Exam Material

Understanding foundational concepts is essential for success in general chemistry. The following topics from earlier chapters are still required knowledge:

• SI Prefixes and Units: Know the metric prefixes from mega (106) to nano (10-9). Remember that 1 mL = 1 cm3.

• Significant Figures: Be able to determine and use significant figures correctly in calculations.

• Diatomic Elements: The seven elements that exist as diatomic molecules are H2, N2, O2, F2, Cl2, Br2, and I2.

• Ionic vs. Molecular Compounds: Distinguish between compounds formed from ions (ionic) and those formed from molecules (molecular).

• Empirical Formulas and Naming: Determine empirical formulas and names for ionic compounds, including those with polyatomic ions and transition metals.

• Binary Molecular Compounds: Name and write formulas for binary molecular compounds using prefixes (mono- to deca-).

• Chemical Equations: Write and balance chemical equations to represent reactions.

• Molar Mass Calculations: Calculate molar mass for elements, ions, and compounds. Use molar mass to convert between moles and grams.

Stoichiometry

Stoichiometry involves relating quantities of reactants and products in chemical reactions using balanced equations.

• Mass-Mole Interconversions: Use molar mass to convert between mass and moles for reactants and products.

• Limiting Reagent: Identify the reactant that limits the amount of product formed.

• Excess Reagent: Calculate the amount of reactant left over after the reaction.

• Percent Yield: Calculate the efficiency of a reaction using the formula:

Example: If 10 g of reactant A produces 8 g of product B, but the theoretical yield is 10 g, then percent yield is .

Solutions and Molarity

Solutions are homogeneous mixtures of solute and solvent. Molarity is a key measure of concentration.

• Molarity (M): Defined as moles of solute per liter of solution.

• Preparation of Solutions: To prepare a solution, dissolve the solute in a portion of solvent, then dilute to the desired final volume.

• Calculating Moles and Mass: Use molarity and volume to find moles or grams of solute:

• Dilution: To dilute a solution, use: where and are the initial concentration and volume, and and are the final concentration and volume.

• Concentration of Ions: Calculate concentrations of formula units, specific ions, and total ions in a solution.

Example: To prepare 250 mL of 0.1 M NaCl, dissolve 0.025 mol NaCl (1.46 g) in water and dilute to 250 mL.

Stoichiometry in Solution Reactions

Stoichiometric calculations can be applied to reactions in solution, such as precipitation and neutralization.

• Precipitation Reactions: Use molarity and volume to determine moles of reactants and products.

• Neutralization Reactions: Calculate the amount of acid or base required for complete reaction.

Example: Mixing 0.1 M AgNO3 and 0.1 M NaCl produces AgCl precipitate. Use stoichiometry to determine the amount formed.

Electrolytes and Dissolution Processes

Electrolytes are substances that produce ions in solution. Their behavior depends on their chemical nature.

• Strong Electrolytes: Completely dissociate in water (e.g., NaCl, strong acids).

• Weak Electrolytes: Partially ionize (e.g., acetic acid).

• Nonelectrolytes: Do not produce ions (e.g., sugar).

• Dissolution Processes:

  • Strong Acids: Complete ionization:

  • Weak Acids/Bases: Partial ionization:

  • Soluble Ionic Compounds: Dissociation:

  • Nonelectrolytes: Simple dissolution, no ions produced.

• Writing Dissolution Equations: Write complete and balanced equations for dissolution of ionic compounds, acids, bases, and nonelectrolytes.

Precipitation Reactions (Metathesis/Double Displacement)

Precipitation reactions involve the formation of an insoluble product from soluble reactants.

• Solubility Rules: Use solubility rules to predict if a compound will precipitate.

• Double Displacement (Metathesis): Two compounds exchange ions to form new products.

• Writing Equations: Represent reactions as molecular, complete ionic, and net ionic equations.

• Spectator Ions: Ions that do not participate in the reaction remain unchanged.

Example: Mixing Na2SO4 and BaCl2 forms BaSO4 precipitate.

Acids and Bases

Acids and bases are classified by their strength and their behavior in water.

• Strong Acids: Know the names and formulas for the seven strong acids:

  • Hydrochloric acid (HCl)

  • Hydrobromic acid (HBr)

  • Hydroiodic acid (HI)

  • Nitric acid (HNO3)

  • Perchloric acid (HClO4)

  • Sulfuric acid (H2SO4)

  • Chloric acid (HClO3)

• Strong Bases: Typically group 1 and 2 hydroxides (e.g., NaOH, KOH, Ca(OH)2).

• Acid Identification: Acids usually have H at the front of the formula.

• Dissolution Representation:

  • Strong acids: Complete dissociation ()

  • Weak acids: Partial dissociation ()

Neutralization Reactions

Neutralization is a type of double displacement reaction between an acid and a base, producing water and a salt.

• Predicting Products: Combine H+ from acid and OH- from base to form H2O; remaining ions form the salt.

• Writing Equations: Write molecular, complete ionic, and net ionic equations for neutralization reactions.

Example: Neutralization of HCl and NaOH:

Additional info: You will be provided with a periodic table and solubility rules during the exam. Use these resources to assist with identifying elements, compounds, and solubility predictions.