Chemistry Study Guide for GOB College Courses

Atoms

The study of atoms forms the foundation of chemistry, focusing on their structure, properties, and behavior.

• Atomic Theory: Explains that all matter is composed of atoms, which are the smallest units of elements.

• Elements and Atomic Number: Each element is defined by its atomic number, which is the number of protons in its nucleus.

• Isotopes and Atomic Weight: Isotopes are atoms of the same element with different numbers of neutrons. Atomic weight is the weighted average mass of an element's isotopes.

• Example: Carbon-12 and Carbon-14 are isotopes of carbon.

The Periodic Table

The periodic table organizes elements based on their atomic number and recurring chemical properties.

• Periodic Table Structure: Elements are arranged in periods (rows) and groups (columns) with similar properties.

• Electronic Structure of Atoms: Electrons are arranged in shells and subshells around the nucleus.

• Electron Configurations: The distribution of electrons among the orbitals of an atom.

• Relationship to Periodic Table: Electron configurations determine an element's position and chemical behavior.

• Example: Sodium (Na) has an electron configuration of .

Classification and Balancing of Chemical Reactions

Chemical reactions are classified by the changes that occur and must be balanced to obey the law of conservation of mass.

• Classes of Chemical Reactions: Synthesis, decomposition, single replacement, double replacement, and combustion.

• Acids, Bases, and Neutralization: Acids donate protons (H+), bases accept protons; neutralization produces water and a salt.

• Redox Reactions: Involve the transfer of electrons between species.

• Balancing Reactions: The number of atoms of each element must be equal on both sides of the equation.

• Example:

Mole and Mass Relationships

The mole is a fundamental unit in chemistry for counting particles, relating mass to number of entities.

• The Mole and Avogadro’s Number: One mole contains entities (Avogadro's number).

• Gram–Mole Conversions:

• Example: 18 g of water () is 1 mole, since molar mass is 18 g/mol.

Reaction Rates and Chemical Equilibria

Understanding how fast reactions occur and how they reach equilibrium is essential in chemistry.

• Endothermic and Exothermic Reactions: Endothermic reactions absorb energy; exothermic reactions release energy.

• Factors Influencing Reaction Rates: Temperature, concentration, surface area, catalysts.

• Chemical Equilibrium: The state where the forward and reverse reaction rates are equal.

• Equilibrium Constant (): (concentrations at equilibrium)

• Example:

Nuclear Chemistry

Nuclear chemistry deals with changes in the nucleus, including radioactivity and nuclear reactions.

• Radioactivity: Spontaneous emission of particles or energy from unstable nuclei (alpha, beta, gamma decay).

• Conservation Laws: Conservation of nucleon number and charge in nuclear reactions.

• Law of Radioactive Decay: , where is the number of undecayed nuclei, is the decay constant.

• Half-life (): Time required for half the nuclei to decay:

Physical Quantities

Measurement in chemistry relies on standardized units and significant figures for accuracy.

• Metric System: Standard units for length (meter), mass (gram), and volume (liter).

• Significant Figures: Digits in a measurement that are known with certainty plus one estimated digit.

• Example: 0.00450 has three significant figures.

Chemical Calculations

Chemical calculations involve using formulas and equations to determine quantities in reactions.

• Mole Concept and Chemical Formulas: Relate the number of moles to mass and chemical composition.

• Stoichiometry: Calculations involving reactants and products in chemical equations.

• Volume and Concentration:

Solutions

Solutions are homogeneous mixtures with important properties and calculations.

• Mixtures and Solutions: Solutions are uniform mixtures of solute and solvent.

• Units of Concentration: Molarity (M), percent by mass, percent by volume.

• Dilution:

• Electrolytes: Substances that dissociate into ions in solution, conducting electricity.

Acids and Bases

Acids and bases are fundamental chemical species with characteristic properties and reactions.

• pH Definition:

• Acids and Bases in Aqueous Solution: Acids increase , bases increase .

• Common Acids and Bases: HCl, H2SO4, NaOH, NH3

Alcohols

Alcohols are organic compounds with a hydroxyl (-OH) group attached to a carbon atom.

• Common Alcohols: Methanol, ethanol, isopropanol.

• Naming Alcohols: Based on the longest carbon chain containing the -OH group.

• Properties: Solubility in water, boiling points, acidity.

• Reactions: Oxidation, dehydration, substitution.

Amino Acids and Proteins

Amino acids are the building blocks of proteins, with both acidic and basic properties.

• Structures: Central carbon, amino group, carboxyl group, side chain (R group).

• Acid–Base Properties: Zwitterion formation at physiological pH.

• Chemical Properties of Proteins: Peptide bond formation, denaturation, enzymatic activity.

Enzymes and Vitamins

Enzymes are biological catalysts, and vitamins are essential organic nutrients.

• Catalysis by Enzymes: Enzymes lower activation energy, increasing reaction rates.

• How Enzymes Work: Substrate binding, active site specificity, induced fit model.

• Vitamins and Minerals: Essential for enzyme function and metabolic processes.

Carbohydrates

Carbohydrates are energy-providing biomolecules classified by their structure.

• Classification: Monosaccharides, disaccharides, polysaccharides.

• D and L Families: Stereoisomers based on the configuration of the chiral carbon farthest from the carbonyl group.

• Structure of Glucose: Six-carbon aldose sugar.

• Important Polysaccharides: Starch, glycogen, cellulose.

• Properties: Solubility, sweetness, reactivity.

Lipids

Lipids are hydrophobic biomolecules, including fats, oils, and related compounds.

• Structure and Classification: Fatty acids, triglycerides, phospholipids, steroids.

• Fatty Acids and Esters: Saturated and unsaturated fatty acids; esterification forms triglycerides.

• Properties: Melting point, solubility, energy storage.

Nucleic Acids and Protein Synthesis

Nucleic acids store and transmit genetic information, directing protein synthesis.

• DNA, Chromosomes, and Genes: DNA is organized into chromosomes, which contain genes.

• Composition of Nucleic Acids: Nucleotides composed of a sugar, phosphate, and nitrogenous base.

• Structure of Nucleic Acid Chains: Polynucleotide chains with specific base sequences.

• Base Pairing in DNA: Watson–Crick model: pairs with , pairs with .

Summary Table: Key Chemistry Topics