General Chemistry: Chemical Reactions, Stoichiometry, and Solutions Study Guide

Ch.4: Chemical Reactions and Stoichiometry

Key Terms and Concepts

• Reactants and Products: Substances consumed and formed during a chemical reaction.

• Chemical Equations: Representation of chemical reactions using symbols and formulas.

Writing and Balancing Chemical Equations

• Balancing Equations: Adjusting coefficients to ensure the same number of each atom on both sides of the equation.

• Polyatomic Ions: Treat polyatomic ions as units when balancing if they appear unchanged on both sides.

• State Labels: Indicate the physical state of each substance: (s) for solid, (l) for liquid, (g) for gas, (aq) for aqueous solution.

• Example: $2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$

Stoichiometry and Mole Calculations

• Mole-to-Mole Conversions: Use coefficients from balanced equations to relate moles of reactants and products.

• Limiting Reactant: The reactant that is completely consumed first, limiting the amount of product formed.

• Theoretical Yield: The maximum amount of product that can be formed from given reactants.

• Percent Yield: $\text{Percent Yield} = \frac{\text{Actual Yield}}{\text{Theoretical Yield}} \times 100\%$

• Example: If 5.0 g of A reacts with excess B to produce 4.0 g of C, and the theoretical yield is 5.5 g, then $\text{Percent Yield} = \frac{4.0}{5.5} \times 100\% = 72.7\%$

Mass-to-Mole and Mole-to-Mass Calculations

• Use molar mass to convert between mass and moles: $\text{Moles} = \frac{\text{Mass (g)}}{\text{Molar Mass (g/mol)}}$

• Apply stoichiometric coefficients to relate moles of different substances in a reaction.

Ch.5: Solutions and Aqueous Reactions

Solution Terminology

• Solution: Homogeneous mixture of two or more substances.

• Solvent: The substance present in the greatest amount; dissolves the solute.

• Solute: The substance dissolved in the solvent.

• Molarity (M): $\text{Molarity} = \frac{\text{Moles of Solute}}{\text{Liters of Solution}}$

Solution Preparation and Dilution

• Calculating Molarity: Use mass and volume to determine the concentration of a solution.

• Dilution: $M_1V_1 = M_2V_2$ (where $M$ is molarity and $V$ is volume before and after dilution).

• Recipe Calculation: Determine the mass of solute needed to prepare a solution of desired concentration and volume.

Solution Dilution and Stoichiometry

• Solution Dilution Calculations: Use the dilution equation to find new concentrations or volumes after adding solvent.

• Stoichiometry in Solutions: Use volume and concentration to find moles, then apply stoichiometry to solve for unknowns.

Electrolytes and Conductivity

• Electrolyte: Substance that conducts electricity when dissolved in water (produces ions).

• Nonelectrolyte: Substance that does not produce ions in solution; does not conduct electricity.

• Weak Electrolyte: Partially ionizes in solution; conducts electricity weakly.

• Examples: NaCl (strong electrolyte), sugar (nonelectrolyte), acetic acid (weak electrolyte).

Precipitation Reactions and Solubility

• Precipitation Reaction: Reaction in which an insoluble solid (precipitate) forms when two solutions are mixed.

• Solubility Rules: Guidelines to predict whether a compound will dissolve in water or form a precipitate.

• Application: Use solubility rules to determine if a reaction will produce a precipitate.

• Example: Mixing solutions of AgNO$_3$ and NaCl forms AgCl(s) as a precipitate.

Writing Ionic Equations

• Molecular Equation: Shows all reactants and products as compounds.

• Complete Ionic Equation: Shows all strong electrolytes as ions.

• Net Ionic Equation: Shows only the species that actually change during the reaction.

• Spectator Ions: Ions that do not participate in the actual chemical change.

• Example:

  • Molecular: $\text{AgNO}_3(aq) + \text{NaCl}(aq) \rightarrow \text{AgCl}(s) + \text{NaNO}_3(aq)$

  • Complete Ionic: $\text{Ag}^+(aq) + \text{NO}_3^-(aq) + \text{Na}^+(aq) + \text{Cl}^-(aq) \rightarrow \text{AgCl}(s) + \text{Na}^+(aq) + \text{NO}_3^-(aq)$

  • Net Ionic: $\text{Ag}^+(aq) + \text{Cl}^-(aq) \rightarrow \text{AgCl}(s)$

Acid-Base and Redox Reactions

• Acid-Base Reactions: Involve transfer of protons (H$^+$) between reactants.

• Redox Reactions: Involve transfer of electrons; oxidation is loss of electrons, reduction is gain of electrons.

• Oxidation Numbers: Assigned to atoms to track electron transfer; follow specific rules for assignment.

• Example: In $\text{Zn}(s) + \text{Cu}^{2+}(aq) \rightarrow \text{Zn}^{2+}(aq) + \text{Cu}(s)$, Zn is oxidized, Cu$^{2+}$ is reduced.

Summary Table: Types of Electrolytes

Type	Definition	Example
Strong Electrolyte	Completely dissociates into ions in solution	NaCl, HCl
Weak Electrolyte	Partially dissociates into ions	CH3COOH (acetic acid)
Nonelectrolyte	Does not dissociate into ions	Sucrose (table sugar)

Summary Table: Common Solubility Rules

Compound Type	Solubility	Exceptions
All nitrates (NO3-)	Soluble	None
All chlorides (Cl-)	Soluble	Ag+, Pb2+, Hg22+
All sulfates (SO42-)	Soluble	Ba2+, Pb2+, Ca2+, Sr2+
All carbonates (CO32-)	Insoluble	Group 1A, NH4+

Additional info: Some explanations and examples have been expanded for clarity and completeness, as the original notes were in outline form.