General Chemistry Study Notes

Atomic Structure

Atomic structure is fundamental to understanding chemical properties and reactions. It involves the arrangement of subatomic particles (protons, neutrons, electrons) and the quantization of energy.

• Energy of a photon: Where is energy, is Planck's constant ( J·s), and is frequency.

• Relationship between frequency and wavelength: Where is the speed of light ( m/s), is wavelength, and is frequency.

• Avogadro's number: mol−1

Example: Calculating the energy of a photon with a wavelength of 500 nm.

Gases

The behavior of gases is described by several laws and equations, which relate pressure, volume, temperature, and amount of gas.

• Density:

• Temperature conversion:

• Partial pressure:

• Ideal Gas Law: Where is pressure, is volume, is moles, is the gas constant ( L·atm/mol·K), and is temperature in Kelvin.

• STP (Standard Temperature and Pressure): (273 K), atm, mol of ideal gas = L at STP.

Example: Calculating the volume of a gas at STP given moles.

Solutions

Solutions are homogeneous mixtures of solutes dissolved in solvents. Their properties depend on concentration and the nature of the solute and solvent.

• Molarity:

• Molality:

• Percent yield:

• Percent error:

• Colligative properties: (freezing point depression), (boiling point elevation)

Example: Calculating the molarity of a solution given moles and volume.

Calorimetry and Thermodynamics

Thermodynamics studies energy changes in chemical reactions, especially heat transfer and enthalpy changes.

• Heat transfer: Where is heat, is mass, is specific heat capacity, is temperature change.

• Enthalpy change:

• Entropy change:

Example: Calculating the heat absorbed by water when its temperature increases.

Acids, Bases, and Equilibrium

Acids and bases are classified by their ability to donate or accept protons. Chemical equilibrium describes the state where the rates of forward and reverse reactions are equal.

• pH and pOH: , ,

• Equilibrium constant for water:

• General equilibrium constant: for

• Solubility product constant:

Example: Calculating the pH of a solution with a known .

Periodic Table and Atomic Properties

The periodic table organizes elements by increasing atomic number and recurring chemical properties. Trends such as electronegativity, atomic radius, and ionization energy are important for predicting element behavior.

• Groups: Vertical columns with similar chemical properties.

• Periods: Horizontal rows indicating energy levels.

• Metals, nonmetals, metalloids: Classified by physical and chemical properties.

Example: Identifying the group and period of sodium (Na).

Stoichiometry

Stoichiometry involves quantitative relationships in chemical reactions, allowing calculation of reactant and product amounts.

• Mole ratio: Derived from balanced chemical equations.

• Limiting reactant: The reactant that determines the maximum amount of product formed.

• Theoretical yield: Maximum amount of product possible from given reactants.

Example: Calculating the mass of product formed from given reactant masses.

Empirical and Molecular Formulas

Empirical formulas show the simplest whole-number ratio of elements in a compound, while molecular formulas show the actual number of atoms.

• Empirical formula: Simplest ratio of elements.

• Molecular formula: Actual number of atoms of each element.

Example: Determining the empirical formula from percent composition data.

Activity Series of Metals

The activity series ranks metals by their reactivity, predicting the outcome of single displacement reactions.

Example: Predicting whether Zn will displace Cu from CuSO4 solution.

Colligative Properties

Colligative properties depend on the number of solute particles in a solution, not their identity. These include boiling point elevation and freezing point depression.

• Freezing point depression:

• Boiling point elevation:

Example: Calculating the freezing point of a solution given and molality.

Sample Reference Table: Chemistry Constants and Equations

Additional info: These notes are based on the reference sheet and sample questions from an official ACT International Subject Test—Chemistry Practice Test. They cover essential formulas, definitions, and concepts for college-level General Chemistry.