General Chemistry I Final Exam Review: Key Concepts and Practice Problems

Final Exam Review: General Chemistry I

Matter and Measurements

This section covers the basic definitions and distinctions in chemistry, including the nature of matter, compounds, mixtures, and measurement units.

• Compound vs. Mixture: A compound is a substance formed when two or more elements are chemically bonded in fixed proportions (e.g., water, H2O). A mixture consists of two or more substances physically combined, not chemically bonded (e.g., air).

• Significant Figures: The number of significant digits in a measurement reflects its precision. For example, 18.0 has three significant figures.

• Unit Conversions: Converting between units (e.g., grams to moles) is essential for quantitative chemistry.

• Example: Calculate the number of moles in 7.50 g of lithium metal using its molar mass.

Elements, Atoms, and the Laws of Chemical Combination

Understanding atomic structure and chemical laws is fundamental to chemistry.

• Atomic Number: The number of protons in an atom defines the element.

• Isotopes: Atoms of the same element with different numbers of neutrons.

• Law of Conservation of Mass: Mass is conserved in chemical reactions.

• Example: Calculate the number of atoms in a given mass of calcium.

Quantum Mechanics, Electron Configurations, and Periodic Trends

This topic explores how electrons are arranged in atoms and how this affects chemical properties.

• Electron Configuration: The arrangement of electrons in shells and subshells (e.g., 1s2 2s2 2p6).

• Periodic Trends: Properties such as atomic radius, ionization energy, and electronegativity change predictably across the periodic table.

• Example: Write the electron configuration for Ca.

Chemical Bonding, Molecular Structures and Shapes

Chemical bonds form between atoms to create molecules with specific shapes and properties.

• Ionic vs. Covalent Bonds: Ionic bonds involve electron transfer; covalent bonds involve electron sharing.

• Lewis Structures: Diagrams showing valence electrons and bonding in molecules.

• Polarity: Molecules are polar if they have an uneven distribution of charge.

• Example: Draw the Lewis structure for HCN and determine if it is polar.

Compounds, Solutions, and Their Composition

Solutions are homogeneous mixtures, and their composition can be described quantitatively.

• Molarity (M): The concentration of a solution, defined as moles of solute per liter of solution.

• Example: Calculate the molarity of a solution made by dissolving 8.5 g of KBr in 250 mL of water.

Chemical Reactions and Stoichiometry

Stoichiometry involves calculating the quantities of reactants and products in chemical reactions.

• Balanced Equations: Chemical equations must be balanced to obey the law of conservation of mass.

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

• Example: For the reaction $2AgNO_3(aq) + Na_2CO_3(aq) \rightarrow Ag_2CO_3(s) + 2NaNO_3(aq)$, calculate the mass of Ag2CO3 formed from given reactant masses.

Gases and Their Properties

The behavior of gases is described by several laws relating pressure, volume, temperature, and amount.

• Ideal Gas Law: $PV = nRT$

• Boyle's Law: $P_1V_1 = P_2V_2$ (at constant temperature)

• Charles's Law: $\frac{V_1}{T_1} = \frac{V_2}{T_2}$ (at constant pressure)

• Example: Calculate the volume a gas will occupy at different temperatures and pressures.

Thermochemical Aspects of Chemical Reactions

Thermochemistry studies the energy changes during chemical reactions.

• Endothermic vs. Exothermic: Endothermic reactions absorb heat; exothermic reactions release heat.

• Specific Heat: The amount of heat required to raise the temperature of 1 g of a substance by 1°C.

• Example: Calculate the heat required to raise the temperature of water.

Chemical Equilibrium

Chemical equilibrium occurs when the rates of the forward and reverse reactions are equal.

• Equilibrium Constant (K): $K = \frac{[products]}{[reactants]}$ (at equilibrium)

• Le Châtelier's Principle: The system shifts to counteract changes in concentration, pressure, or temperature.

• Example: Predict the effect of temperature increase on the equilibrium position.

Acid and Base Equilibrium

Acids and bases react in aqueous solutions, and their strengths are quantified by equilibrium constants.

• pH Calculation: $pH = -\log[H^+]$

• Strong vs. Weak Acids/Bases: Strong acids/bases dissociate completely; weak ones do not.

• Example: Calculate the pH of a solution with a given concentration of HCl.

Electrochemical Processes and Reactions

Electrochemistry involves redox reactions and the flow of electrons in cells.

• Oxidation and Reduction: Oxidation is loss of electrons; reduction is gain of electrons.

• Balancing Redox Equations: Use the half-reaction method to balance electrons transferred.

• Example: Balance the equation $Fe_2O_3 + CO \rightarrow Fe + CO_2$ and identify oxidized/reduced species.

Reaction Kinetics

Kinetics studies the rates of chemical reactions and factors affecting them.

• Rate Law: $\text{Rate} = k[A]^m[B]^n$

• Effect of Temperature: Increasing temperature generally increases reaction rate.

• Example: Calculate how long it will take for a reaction to reach a certain concentration.

Mathematical Operations and Functions

Mathematical skills are essential for solving chemistry problems, including algebraic manipulation and unit conversions.

• Dimensional Analysis: A method for converting units using conversion factors.

• Example: Convert 7.50 g of lithium to moles using its molar mass.

Lab Techniques and Procedures

Basic laboratory skills include measuring, mixing, and observing chemical reactions safely and accurately.

• Solution Preparation: Calculating the amount of solute needed for a desired concentration.

• Example: Prepare 250 mL of 0.10 M NaCl solution.

Sample Table: Comparison of Compound and Mixture

Property	Compound	Mixture
Composition	Fixed, definite	Variable
Separation	Chemical methods	Physical methods
Examples	Water (H2O), Sodium chloride (NaCl)	Air, Salt water

Additional info:

• Some questions require calculation steps, such as using molar mass, gas laws, and stoichiometry.

• Redox reactions and balancing equations are included, relevant to electrochemistry.

• Questions on molecular polarity and Lewis structures relate to chemical bonding and molecular shapes.

• Lab-based questions (solution preparation, concentration) are included.