Chemical Bonding and Solutions: A Comprehensive Guide
Chemical Bonding
Ionic Bonding
Chemical bonding that results from the electrical attraction between cations and anions
Covalent Bonding
Results from the sharing of electron pairs between two atoms
Types of Covalent Bonds
- Nonpolar Covalent Bond: A covalent bond in which the bonding electrons are shared equally by the bonded atoms, resulting in a balanced distribution of electrical charge.
- Polar Covalent Bond: Covalent bond in which the bonded atoms have an unequal attraction for the shared electrons
Key Concepts in Covalent Bonding
- Electronegativity: A measure of an atom’s ability to attract electrons
- Polar: Uneven distribution of charge
- Molecule: A neutral group of atoms that are held together by covalent bonds
- Molecular Compound: Chemical compound whose simplest units are molecules
- Chemical Formula: Indicates the relative numbers of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts
- Molecular Formula: Indicates the types and numbers of atoms combined in a single molecule of a molecular compound
- Diatomic Molecule: A molecule containing only 2 atoms
- Bond Energy: Energy required to break a covalent bond and form neutral isolated atoms
- Resonance: The bonding in molecules or ions that cannot be correctly represented by a single Lewis structure
Ionic Compounds
Positive and negative ions (cations and anions) that are combined so that the numbers of positive and negative charges are equal
Key Concepts in Ionic Compounds
- Formula Unit: Simplest collection of atoms from which an ionic compound formula can be established
- Lattice Energy: Energy released when one mole of an ionic crystalline compound is formed from gaseous ions
- Polyatomic Ions: A charged group of covalently bonded atoms
Metallic Bonding
Chemical bonding resulting from the attraction between metal atoms and the surrounding sea of electrons.
Properties of Metals
- Malleability: The ability of a substance to be hammered or beaten into thin sheets.
- Ductility: The ability of a substance to be drawn, pulled, or extruded through a small opening to produce a wire.
Molecular Geometry and Intermolecular Forces
VSEPR Theory
Valence-Shell Electron Pair Repulsion Theory
Repulsion between the sets of valence-level electrons surrounding an atom causes the sets to be oriented as far apart as possible
Intermolecular Forces
- Dipole-Dipole Forces: Forces of attraction between polar molecules
- Dipole: Created by equal but opposite charges that are separated by a short distance
- London Dispersion Forces: The intermolecular attractions resulting from the constant motion of electrons and the creation of instantaneous dipoles; forces act between all atoms and molecules; forces are not present in intramolecular forces; increases with atomic mass or molar mass.
Hybridization
The mixing of two or more atomic orbitals of similar energies on the same atom to produce new orbitals of equal energies.
- Hybrid Orbitals: Orbitals of equal energy produced by the combination of two or more orbitals on the same atom.
Chemical Nomenclature
Types of Ions and Compounds
- Monatomic Ions: Ions formed from a single atom
- Binary Compounds: Compounds composed of two elements
- Oxyanions: Polyatomic ions that contain oxygen
- Binary Acids: Acids that consist of two elements, usually hydrogen and one of the halogens—fluorine, chlorine, bromine, iodine
- Oxyacids: Acids that contain hydrogen, oxygen, and a third element (usually a nonmetal)
- Salt: Ionic compound composed of a cation and the anion from an acid
Chemical Formulas and Mass
- Formula Mass: Sum of the average atomic masses of all atoms represented in its formula
- Empirical Formula: A chemical formula that shows the composition of a compound in terms of the relative numbers and kinds of atoms in the simplest ratio
- Hydrocarbons: Molecular compounds composed solely of carbon and hydrogen
- Stock System: Used to distinguish the ions formed when elements form two or more cations with different charges; uses a Roman numeral to indicate an ion’s charge
- Molar Mass: The mass in grams of one mole of a substance; a compound’s molar mass is numerically equal to its formula mass.
Chemical Reactions
Types of Chemical Reactions
- Precipitate: A solid that forms from a solution during a chemical reaction
- Reversible Reaction: A chemical reaction in which the products re-form the original reactants
- Synthesis Reaction: A reaction in which two or more substances combine to form a new compound
- Decomposition Reaction: A reaction in which a single compound breaks down to form two or more simpler substances
- Electrolysis: The decomposition of a substance by an electric current
- Single-Displacement Reaction: A reaction in which atoms of one element take the place of atoms of another element in a compound
- Double-Displacement Reaction: When the positive ion of one compound replaces the positive ion of another to form two new compounds.
- Combustion Reaction: A chemical reaction that occurs when a substance reacts with oxygen, releasing energy in the form of heat and light
Reaction Stoichiometry
- Activity Series: A list of elements organized according to the ease with which the elements undergo certain chemical reactions
- Composition Stoichiometry: Deals with the mass relationships of elements in compounds
- Reaction Stoichiometry: Calculations involving the mass relationships between reactants and products in a chemical reaction
- Mole Ratio: A conversion factor that relates the amounts in moles of any two substances involved in a chemical reaction
- Limiting Reactant: The substance that controls the quantity of product that can form in a chemical reaction
- Excess Reactant: The substance that is not used up completely in a reaction
- Theoretical Yield: The maximum amount of product that can be produced from a given amount of reactant
- Actual Yield: The measured amount of a product obtained from a reaction
- Percentage Yield: The ratio of the actual yield to the theoretical yield, multiplied by 100
Gases
Kinetic Molecular Theory
Based on the idea that particles of matter are always in motion
Gas Behavior
- Diffusion: Spontaneous mixing of the particles of two substances caused by their random motion
- Effusion: A process by which gas particles pass through tiny openings
- Elastic Collision: Collisions between gas particles, other particles, and container walls—with no net loss of kinetic energy
- Fluids: Liquids or gases that flow
- Ideal Gas: An imaginary gas that perfectly fits all assumptions of the Kinetic Molecular Theory
- Real Gas: A gas that does not behave completely according to the assumptions of the Kinetic Molecular Theory
Gas Laws
- Atmospheric Pressure (Atm): Defined as equivalent to 760 mm Hg
- Barometer: A device used to measure atmospheric pressure
- Standard Temperature & Pressure (STP): Standard conditions of atmospheric pressure and zero degrees Celsius
- Boyle’s Law: The volume of a fixed mass of gas at constant temperature varies inversely with pressure.
- Charles’ Law: The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature.
- Dalton’s Law of Partial Pressures: The total pressure of a mixture of gases is equal to the sum of the partial pressures of the component gases.
- Gay-Lussac’s Law: The pressure of a fixed amount of gas at constant volume varies directly with the Kelvin temperature.
- Combined Gas Law: Expresses the relationship between pressure, volume, and temperature of a fixed amount of gas.
- Avogadro’s Law: States that equal volumes of gases at the same temperature and pressure contain equal numbers of molecules.
- Ideal Gas Law: The mathematical relationship among pressure, volume, temperature, and the number of moles of a gas.
- Graham’s Law of Effusion: States that the rates of effusion of gases at the same temperature and pressure are inversely proportional to the square roots of their molar masses.
Solutions
Types of Mixtures
- Solution: A homogeneous mixture of two or more substances in a single phase
- Homogeneous: Same throughout
- Heterogeneous: Different throughout
- Suspensions: Heterogeneous mixture in which the particles will settle upon standing, can be separated by filtration, and will show the Tyndall effect (e.g., orange juice with pulp)
- Colloid: Heterogeneous mixture with particles smaller than a suspension and larger than a solution. Do not separate upon standing, do not separate by filtration, but can show the Tyndall effect
Solubility
- Soluble: Able to be dissolved
- Insoluble: Not able to be dissolved
- Solvent: The component of the mixture that does the dissolving
- Solute: The substance that is dissolved
- Electrolyte: Substance that dissolves in water to produce ions, therefore the solution can conduct electricity
- Nonelectrolyte: Substance that dissolves in water but does not break into ions and cannot conduct electricity
- Molarity: Moles of solute/liters of solution; M
- Factors Affecting the Rate of Dissolution: Increasing the surface area of the solute, agitation, heating
- Solution Equilibrium: The physical state in which the opposing processes of dissolution and crystallization of a solute occur at equal rates
- Saturated: Contains the maximum amount of dissolved solute
- Unsaturated: Contains less than the maximum amount of solute
- Supersaturated: Contains more solute than a saturated solution under the same conditions
- Solubility Values: States the amount of a specific substance required to form a saturated solution with a specific amount of solvent at a specified temperature
- Immiscible: When two liquids will not dissolve in each other (e.g., water and oil)
- Miscible: Liquids that dissolve freely in one another in any proportion (e.g., ethanol and water)
- Henry’s Law: The solubility of a gas in a liquid is directly proportional to the partial pressure of that gas on the surface of the liquid
- Effervescence: The rapid escape of gas from a liquid in which it is dissolved
- Solvated: A solute particle that is surrounded by solvent molecules
- Enthalpy of Solution: The amount of heat energy absorbed or released when a specific amount of solute dissolves in a solvent
- Concentrated: Contains a large amount of solute