Chemistry Basics: The Mole, Molar Mass, and Unit Conversions

The Mole and Avogadro’s Number

The mole is a fundamental unit in chemistry used to count particles such as atoms, molecules, or ions. Avogadro’s number defines the number of particles in one mole.

• Mole: One mole contains particles (Avogadro’s number).

• Avogadro’s Number: particles/mole.

• Example: One mole of water contains molecules of H2O.

Molar Mass Calculation

Molar mass is the mass of one mole of a substance, expressed in grams per mole (g/mol).

• Calculation: Add the atomic masses of all atoms in the compound.

• Formula:

• Example: Molar mass of NaCl: Na (22.99 g/mol) + Cl (35.45 g/mol) = 58.44 g/mol.

Unit Conversions: Mole, Particles, and Grams

Chemists often convert between moles, number of particles, and mass.

• Mole to Particles: Multiply moles by Avogadro’s number.

• Mole to Mass: Multiply moles by molar mass.

• Mass to Moles: Divide mass by molar mass.

• Example:

• Example:

Introduction to Organic Chemistry

Organic vs. Inorganic Compounds

Organic compounds contain carbon and are typically found in living organisms, while inorganic compounds do not usually contain carbon-hydrogen bonds.

• Organic Compounds: Contain carbon, often hydrogen, and may include oxygen, nitrogen, etc. Example: CH4 (methane).

• Inorganic Compounds: Do not contain carbon-hydrogen bonds. Example: NaCl (table salt).

Saturated vs. Unsaturated Hydrocarbons

Hydrocarbons are classified based on the types of bonds between carbon atoms.

• Saturated Hydrocarbons: Only single bonds (alkanes).

• Unsaturated Hydrocarbons: Double (alkenes), triple (alkynes), or aromatic rings.

• Example: Ethane (C2H6) is saturated; ethene (C2H4) is unsaturated.

Straight-Chain Alkanes vs. Cycloalkanes

Alkanes can be straight-chain or cyclic.

• Straight-Chain Alkanes: General formula: CnH2n+2.

• Cycloalkanes: General formula: CnH2n.

• Example: Butane (C4H10), cyclobutane (C4H8).

Drawing Organic Compounds

Organic compounds can be represented in several ways:

• Lewis Structure: Shows all atoms and bonds.

• Condensed Structure: Groups atoms together (e.g., CH3CH2OH).

• Skeletal Structure: Lines represent carbon chains; hydrogens are implied.

Unsaturated Hydrocarbons: Alkenes, Alkynes, Aromatics

Unsaturated hydrocarbons contain double, triple, or aromatic bonds.

• Alkenes: At least one C=C double bond.

• Alkynes: At least one C≡C triple bond.

• Aromatics: Benzene ring structure (C6H6).

Common Functional Groups in Organic Molecules

Functional groups determine the chemical properties of organic molecules.

• Alcohol: –OH

• Aldehyde: –CHO

• Ketone: –CO–

• Carboxylic Acid: –COOH

• Amine: –NH2

• Haloalkane: –X (X = Cl, Br, I, F)

Primary, Secondary, and Tertiary Alcohols and Amines

Classification depends on the number of carbon atoms attached to the functional group.

• Primary: Functional group attached to one carbon.

• Secondary: Attached to two carbons.

• Tertiary: Attached to three carbons.

• Example: Ethanol is a primary alcohol; isopropanol is secondary.

IUPAC Naming of Branched-Chain Alkanes, Haloalkanes, and Cycloalkanes

The IUPAC system provides rules for naming organic compounds.

• Branched-Chain Alkanes: Identify longest chain, number carbons, name substituents.

• Haloalkanes: Prefix for halogen (e.g., chloro-, bromo-).

• Cycloalkanes: Prefix "cyclo-" before alkane name.

• Example: 2-bromo-3-methylpentane.

Structural vs. Conformational Isomers

Isomers have the same formula but different structures.

• Structural Isomers: Different connectivity of atoms.

• Conformational Isomers: Same connectivity, different spatial arrangement due to rotation.

Cis and Trans Isomers in Cycloalkanes and Alkenes

Cis-trans isomerism arises from restricted rotation around double bonds or rings.

• Cis Isomer: Substituents on same side.

• Trans Isomer: Substituents on opposite sides.

• Example: cis-2-butene vs. trans-2-butene.

Saturated and Unsaturated Fatty Acids: Skeletal Structures and Classification

Fatty acids can be drawn in skeletal form and classified by bond type and omega number.

• Saturated: No double bonds.

• Unsaturated: One or more double bonds (cis or trans).

• Omega Classification: Position of first double bond from methyl end (omega-3, omega-6, omega-9).

Chiral Centers in Organic Molecules

A chiral center is a carbon atom bonded to four different groups, leading to optical isomerism.

• Chiral Center: Carbon with four distinct substituents.

• Example: Lactic acid has a chiral center.

Chemical Reactions

Thermodynamics: Exo/Endothermicity, Disorder, and Spontaneity

Chemical reactions are characterized by changes in enthalpy (ΔH), entropy (ΔS), and free energy (ΔG).

• Exothermic: Releases heat ().

• Endothermic: Absorbs heat ().

• Disorder: Increase (), decrease ().

• Spontaneity: means spontaneous.

• Formula:

Reaction Energy Diagrams

Energy diagrams illustrate the energy changes during a reaction.

• Exergonic: Products lower in energy than reactants.

• Endergonic: Products higher in energy than reactants.

• Activation Energy: Energy required to start the reaction.

Factors Affecting Reaction Rate

Several factors influence how fast a reaction occurs.

• Temperature: Higher temperature increases rate.

• Reactant Concentration: More reactants increase rate.

• Catalyst: Lowers activation energy, increases rate.

• Enzymes: Biological catalysts.

Energy Content in Food

Food energy is calculated from nutrient molecules.

• Carbohydrates: 4 kcal/g

• Proteins: 4 kcal/g

• Fats: 9 kcal/g

• Formula:

Classification of Chemical Reactions

Reactions are classified by the changes in reactants and products.

• Synthesis: Two or more substances combine.

• Decomposition: One substance breaks into two or more.

• Single Displacement: One element replaces another.

• Double Displacement: Exchange of ions between compounds.

• Combustion: Reaction with oxygen producing CO2 and H2O.

Organic Reaction Types

Organic reactions include oxidation, reduction, condensation, hydrolysis, hydrogenation, and hydration.

• Oxidation: Loss of electrons or hydrogen, gain of oxygen.

• Reduction: Gain of electrons or hydrogen, loss of oxygen.

• Condensation: Two molecules join, releasing water.

• Hydrolysis: Splitting a molecule by adding water.

• Hydrogenation: Addition of hydrogen to unsaturated bonds.

• Hydration: Addition of water to an alkene.

Predicting Products and Balancing Combustion Reactions

Combustion of hydrocarbons produces CO2 and H2O.

• General Equation:

• Balancing: Ensure equal numbers of atoms on both sides.

Oxidation–Reduction Reactions: Inorganic and Organic

Identify which substance is oxidized (loses electrons) and which is reduced (gains electrons).

• Inorganic: Example: Zn + Cu2+ → Zn2+ + Cu

• Organic: Example: Alcohol to aldehyde (oxidation).

Hydrolysis and Condensation in Lipids

Lipids undergo hydrolysis (breakdown) and condensation (formation).

• Hydrolysis: Triglyceride + water → glycerol + fatty acids.

• Condensation: Glycerol + fatty acids → triglyceride + water.

Hydrogenation and Hydration Reactions

Hydrogenation adds hydrogen to unsaturated bonds; hydration adds water to alkenes.

• Hydrogenation: Converts unsaturated fats to saturated fats.

• Hydration: Alkene + water → alcohol.

Additional info: Academic context and examples were added to clarify and expand on brief points from the original material.