General Chemistry Exam 1 Review: Matter, Measurement, Atoms, and Stoichiometry

Exam Preparation and Logistics

What to Bring and Expect

• Required Materials: Number 2 pencil, eraser, non-programmable calculator, full-size scantron sheet, and a valid picture ID.

• Provided in Exam: Periodic table, conversion factors, and extra pages for calculations.

Chapter 1: Introduction to Chemistry, Matter, and Measurement

Introduction to Chemistry

• Elements, Atoms, Molecules: Fundamental building blocks of matter.

Matter: Classification and Properties

• Chemical Properties: Observed when a substance changes into another (e.g., flammability, reactivity).

• Physical Properties: Observed without changing the substance's identity (e.g., boiling point, density).

• Intensive Properties: Independent of amount (e.g., density, color).

• Extensive Properties: Dependent on amount (e.g., mass, volume).

Units of Measurement

• Metric System: Standard units for scientific measurement (meter, kilogram, second, etc.).

Uncertainty in Measurement

• Precision vs. Accuracy: Precision is reproducibility; accuracy is closeness to true value.

• Significant Figures:

  • All nonzero digits are significant.

  • Zeroes between nonzero digits are significant.

  • Leading zeroes are not significant.

  • Trailing zeroes are significant if a decimal is present.

  • Whole numbers ending in zeroes: ambiguity unless written in scientific notation.

Significant Figures in Calculations

• Addition/Subtraction: Result has the same number of decimal places as the measurement with the fewest decimal places.

• Multiplication/Division: Result has the same number of significant figures as the measurement with the fewest significant figures.

Dimensional Analysis

• Definition: Method to convert between units using conversion factors.

• Conversion Factors: Treated as exact; do not affect significant figures.

• Process: Multiply by ratios that cancel unwanted units and introduce desired units.

Chapter 2: Atoms, Molecules, and Ions

The History of Atoms and Molecules

• Development of atomic theory and discovery of subatomic particles.

Atomic Structure

• Protons (p+): Positively charged, in nucleus.

• Neutrons (n0): Neutral, in nucleus.

• Electrons (e-): Negatively charged, outside nucleus.

Atomic Numbers, Mass Numbers, and Isotopes

• Atomic Number (Z): Number of protons.

• Mass Number (A): Number of protons plus neutrons.

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

• Notation: $^A_ZX$ (A = mass number, Z = atomic number, X = element symbol)

• Number of neutrons: $n^0 = A - Z$

The Periodic Table

• Organized by increasing atomic number.

• Groups: Columns with similar chemical properties.

• Metals vs. Nonmetals: Metals on the left, nonmetals on the right.

Molecules and Molecular Compounds

• Chemical Formula: Shows types and numbers of atoms in a molecule.

Ions and Ionic Compounds

• Cations: Positively charged ions (lost electrons).

• Anions: Negatively charged ions (gained electrons).

• Predicting Charges: Based on group number in periodic table.

• Naming: Use Table 2.4 for common cations and anions.

Binary Molecular Compounds

• Naming: Use prefixes (mono-, di-, tri-, etc.) to indicate number of each atom.

Polyanions and Their Nomenclature

• Common polyanions: carbonate (CO32−), nitrate (NO3−), phosphate (PO43−), sulfate (SO42−), perchlorate (ClO4−).

• Naming Rules:

  • "per-...-ate": most oxygen (e.g., perchlorate, ClO4−)

  • "-ate": more oxygen (e.g., chlorate, ClO3−)

  • "-ite": less oxygen (e.g., chlorite, ClO2−)

  • "hypo-...-ite": least oxygen (e.g., hypochlorite, ClO−)

  • With hydrogen: add "hydrogen" or "dihydrogen" (e.g., HCO3− is hydrogen carbonate)

Acid Nomenclature

• Acids: Substances that yield hydrogen ions in water.

• Naming:

  • If anion ends in -ide: add "hydro-" and change to -ic acid (e.g., HCl: hydrochloric acid).

  • If anion ends in -ite: change to -ous acid (e.g., HClO: hypochlorous acid).

  • If anion ends in -ate: change to -ic acid (e.g., HClO3: chloric acid).

• Examples to Learn: Sulfuric acid (H2SO4), Phosphoric acid (H3PO4), Perchloric acid (HClO4), Nitric acid (HNO3), Carbonic acid (H2CO3).

Chapter 3: Chemical Reactions and Stoichiometry

Chemical Equations

• Definition: Symbolic representation of a chemical reaction.

• Balancing Equations: Ensure the same number of each atom on both sides.

Types of Reactions

• Combination: Two or more substances form one product.

• Decomposition: One substance breaks into two or more products.

• Combustion: Substance reacts with oxygen, producing heat and light.

Formula Weights and Percentage Composition

• Formula Weight: Sum of atomic weights in a chemical formula.

• Molecular Weight: Formula weight for molecules.

• Percentage Composition: Mass percent of each element in a compound.

Avogadro's Number and the Mole

• Avogadro's Number: $6.022 \times 10^{23}$ entities per mole.

• Mole: Amount of substance containing Avogadro's number of particles.

Interconverting Masses and Moles

• Key Units: Mass (g), Moles (mol), Molecular Weight (g/mol).

• Conversions:

  • $\frac{g}{mol} \times mol = g$ (MW × moles = mass)

  • $\frac{g}{mol} = \frac{g}{mol} \rightarrow \frac{g}{g} \times mol = mol$ (mass ÷ MW = moles)

• Avogadro's Number: Used to convert between moles and number of molecules/atoms.

Stoichiometry (Preview)

• Limiting Reagent: Reactant that is completely consumed first.

• Theoretical Yield: Maximum amount of product possible.

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

Worked Examples

Dimensional Analysis Example

• Converting units stepwise using conversion factors (e.g., km/day to $/week for gas costs).

• Always cancel units and use exact conversion factors.

Density and Mass Calculation Example

• Given density and composition, calculate mass of a component in a defined volume.

• Example: Calculate mass of oxygen in a room using density and percent composition.

• Equation: $\text{mass} = \text{volume} \times \frac{1000\ L}{1\ m^3} \times \frac{1.19\ g\ air}{1\ L} \times \frac{0.21\ g\ O_2}{1\ g\ air} \times \frac{1\ kg}{1000\ g}$