chemistry final study guide

Mole (mol)

Unit for measuring the amount of substance.

Avogadro's Number

1 mol = 6.022×10^23 particles.

Moles to Particles Conversion

Moles × 6.022×10^23 = particles.

Particles to Moles Conversion

Particles ÷ 6.022×10^23 = moles.

Molar Mass

Mass of 1 mol of a substance, indicated in g/mol.

How to Calculate Grams from Moles

Moles × molar mass = grams.

How to Calculate Moles from Grams

Grams ÷ molar mass = moles.

Percent Composition Formula

% = (mass of element in 1 mol/molar mass of compound) × 100.

Empirical Formula

Lowest whole-number ratio of atoms in a compound.

Molecular Formula

Derived from empirical formula and molecular mass.

RADAR Problem-Solving Strategy

Read, Analyze, Decide, Apply, Reflect.

Physical Change

No change in substance identity (e.g., melting, boiling).

Chemical Change

Produces new substances (e.g., burning, rusting).

Collision Theory

Atoms must collide with enough energy to react.

Law of Conservation of Mass

Matter cannot be created or destroyed; mass of reactants = mass of products.

Word Form Equation Example

Hydrogen gas reacts with oxygen gas to form water.

Chemical Equation Symbols

(s) = solid, (l) = liquid, (g) = gas, (aq) = aqueous.

Reactants

Starting substances in a chemical equation (left side).

Products

Substances formed in a chemical equation (right side).

Coefficients in Equations

Indicate the number of molecules (can change).

Subscripts in Equations

Show the number of atoms in a molecule (cannot change).

Balancing Equations Steps

1. Write unbalanced equation. 2. Count atoms on both sides. 3. Add coefficients to balance. 4. Keep subscripts unchanged.

VSEPR Theory

Valence Shell Electron Pair Repulsion; electron pairs repel and spread out.

Electron Domain

Area of electron density, either a bond or lone pair.

Bonding Pair

Electrons shared between atoms.

Lone Pair

Non-bonded electrons in a molecule.

Trigonal Planar

Molecular shape with 3 bonding domains and 0 lone pairs.

Tetrahedral

Molecular shape with 4 bonding domains and 0 lone pairs.

Bent Molecular Geometry

Shape with 4 electron domains including 2 lone pairs.

3D Notation

Uses wedge-and-dash notation to represent molecular shape.

Intermolecular Forces (IMFs)

Forces between molecules, include London Dispersion, Dipole-Dipole, and Hydrogen Bonding.

Polar Molecules

Unequal sharing of electrons leading to partial charges (e.g., H₂O).

Nonpolar Molecules

Equal sharing of electrons leading to no partial charges.

Hydrogen Bonding

Occurs when H is bonded to N, O, or F, attracting lone pairs on nearby molecules.

Synthesis Reaction

Two or more reactants combine to form one product.

Decomposition Reaction

A single compound breaks into two or more simpler substances.

Combustion Reaction

A substance reacts with oxygen, producing heat/light.

Single Replacement Reaction

One element replaces a similar element in a compound.

Double Replacement Reaction

Ions from two compounds switch places.

Ionic Compounds

Made of positive (cations) and negative (anions) ions.

Cations

Positive ions formed by losing electrons, usually metals.

Anions

Negative ions formed by gaining electrons, usually nonmetals.

Lewis Structures Steps

Draw individual elements, indicate electron transfer, build stable compounds.

Rule of Zero Charge

Total positive and negative charges in a compound must cancel out.

Polyatomic Ions

Groups of atoms acting as a single ion, maintaining their structure.

Transition Metals

Metals that can have multiple charges, indicated with Roman numerals in names.

Chemical Equilibrium Definition

Occurs when forward and reverse reactions happen at the same rate.

Le Chatelier's Principle

A system at equilibrium will shift to counteract disturbances.

Factors Affecting Equilibrium

Concentration changes, pressure changes, and external disturbances influence equilibrium.