Notes, summaries, assignments, exams, and problems for Chemistry

Fundamentals of Organic Chemistry

Hydrocarbons

Alkanes

These are saturated hydrocarbons with single carbon-carbon bonds.

• General Formula: CnH2n+2
• Suffix: -ane
• Prefixes by Carbon Count:
  • 1C: meth-
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Alkenes

Unsaturated hydrocarbons containing at least one carbon-carbon double bond (C=C).

• General Formula: CnH2n
• Suffix: -ene
• Prefixes by Carbon Count:
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Alkynes

Unsaturated hydrocarbons containing at least one carbon-carbon triple bond.

• General Formula: CnH2n-2
• Suffix: -yne
• Prefixes by Carbon Count:
  • 2C: eth-
  • 3C: prop-
  • 4C: but-
  • 5C: pent-
  • 6C: hex-

Common Functional Groups

• Carboxylic Acids: Suffix is -anoic acid.
• Aldehydes: Suffix is -anal.
• Ketones: General structure R-CO-R', where R can be a hydrogen

Principal Components of Iron-Carbon Alloys

The main components of iron-carbon alloys include:

• Perlite: Thin films formed with ferrite (light gray) and cementite (dark gray). Carbon content is 0.89%. Ferrite is softer, while cementite is harder.
• Ferrite: Almost pure iron, very soft, ductile, and magnetic. Its structure is cubic.
• Cementite: Located on the right side of the eutectoid point due to its carbon composition (Fe3C). It is the hardest and most fragile constituent of steel.
• Austenite
• Martensite
• Ledeburite: Consisting of cementite and austenite.

Thermal Treatments for Steel

Thermal treatments modify the properties of steel:

• Tempering: Increases hardness, toughness, and yield strength, but also increases fragility. Methods include immersion in water,

Characteristics of Lipids and Fats

Lipids are a very heterogeneous group of chemicals, both from a structural point of view and regarding the functions they perform. They are primarily composed of carbon, hydrogen, and oxygen, though the latter is usually present in very low proportions. Some lipids also contain phosphorus, nitrogen, and sulfur. Lipids are a group of organic biomolecules that satisfy two distinguishing characteristics: they are insoluble in water and other polar solvents, and they are soluble in organic solvents (i.e., non-polar solvents such as gasoline or benzene).

Molecular Structure of Fatty Acids

Fatty acids are molecules composed of long aliphatic hydrocarbon chains. These are linear chains with an even number of carbon... Continue reading "Biological Functions and Chemical Properties of Lipids" »

Chemical Reactions and Stoichiometry

A chemical reaction is a process by which substances are transformed into others with the release or absorption of energy. Initial substances are called reactants, and the final substances are called products.

Balancing Chemical Equations

Stoichiometry indicates the proportion of molecules (microscopic scale) or moles (macroscopic scale) involved in a reaction to ensure the conservation of atoms. Common balancing methods include:

• Mathematical Method: A matching method consisting of solving a system of equations arising from the equality of atoms on either side of the equation.
• Trial and Error: A method where coefficients are adjusted starting with elements involved in the fewest substances and ending with those

Fundamentals of Polymers

Polymer: Giant organic molecules with molecular weights ranging from 10,000 to 1,000,000 g/mol.

Monomer Unit: The structural entity that is repeated along the polymer molecule.

Monomer + Catalyst → Reactive Monomer Unit

Classification of Polymers

• Mechanism of Polymerization: Addition and condensation.
• Molecular Structure: Linear, branched, and cross-linked.
• Thermal Behavior:
  • Thermoplastics: Plastic polymers that soften when heated and harden upon cooling. This process is reversible; they are typically soft and ductile (e.g., Polyamide via spinning).
  • Thermosets: Plastic polymers that harden irreversibly when heated; they are hard, tough, and fragile (e.g., Melamine via compression).
• Nature of Monomer Units: Homopolymers and

Organic Reactions

Halogenation Substitution of Alkanes

CH₄ + Cl₂ → CH₃Cl + HCl

Obtaining Alcohol from Halogenated Alkanes

CH₃-CH₂-CH₂-CH₂Cl + KOH → CH₃-CH₂-CH₂OH + KCl

Addition Reactions to Double and Triple Bonds

Hydrogenation

Hydrogen is added to alkenes and alkynes to give alkanes in the presence of a metal catalyst.

CH₃-CH=CH-CH₃ + H₂ → CH₃-CH₂-CH₂-CH₃

Halogenation

Alkenes and alkynes react with halogens to give halogenated compounds.

CH₃-CH=CH₂ + Br₂ → CH₃-CHBr-CH₂Br

Adding Hydracids

Acid hydrogen is added to the carbon with more hydrogens (Markovnikov's rule).

CH₂=CH₂ + HI → CH₃CH₂I

Water Addition

Water is added to alkenes in the presence of acid and also follows Markovnikov's rule.

Voltaic Battery

A voltaic battery is a device that allows an... Continue reading "Understanding Organic Reactions, Voltaic Cells, and Salt Hydrolysis" »

Understanding Electrification Phenomena

When rubbing certain materials, two electrical phenomena can be observed: attraction or repulsion. Charles inferred the existence of these two classes of electrical phenomena.

Electrification by Contact

This occurs when an isolated, uncharged body comes into contact with another body already charged by friction. To study this, we utilize an electric pendulum. These experiments show that bodies which have come into contact with other previously electrified bodies also become electrified.

Electrification by Induction

To electrify a body, it is not essential for the charged body to make direct contact with the body you wish to electrify (they can be closer but not touching).

Electric Charge: Definition and Properties

Electric

The material can be a mixture or a pure substance. Materials can be pure substances, which include chemical elements or chemical compounds. For example, Oxygen is a chemical element that cannot be decomposed by chemical procedures. Water is a compound ($\text{H}_2\text{O}$) that can be decomposed into oxygen and hydrogen by chemical methods (like passing an electric current).

The Atom: Building Block of Matter

An atom is the smallest unit that exists in a chemical element. A material is discontinuous and formed by tiny particles called atoms. The size of atoms is on the order of $10^{-12}$ meters (which equals 1 picometer, $\text{pm}$, or $0.000000000001\text{m}$).

Subatomic Particles

• Protons: Carry a positive electric charge ($+$). The charge

Water Hardness

Hard water is water that contains appreciable amounts of dissolved calcium and magnesium compounds. These compounds form insoluble precipitates with soap. Ion exchangers are used to remove the hardness.

Temporary Hardness

Temporary hardness is caused by the presence of calcium and magnesium bicarbonates. It can be eliminated by heating the water to precipitate the calcium carbonate:

Ca(HCO₃)₂ → CaCO₃↓ + CO₂ + H₂O

Permanent Hardness

Permanent hardness refers to the remaining calcium and magnesium salts (not bicarbonates). It requires the addition of chemicals for removal, for example:

Na₂CO₃ + CaCl₂ → CaCO₃↓ + 2NaCl

Water Pollution

Thermal Pollution

Heat, in general, is not considered a contaminant, but its effects on water can... Continue reading "Water Hardness, Pollution, Cleaners, and Sampling" »

Selectivity in Chemical Analysis

A reaction used in chemical analysis is selective when the reaction is characteristic of few substances, showing a preference for some of these. When the reaction is carried out only on a particular substance, it is specific.

Limit of Detection (LOD)

Refers to the minimum amount of a substance that can be detected in a trial.

Sensitivity of Analytical Methods

The ability of a method to discriminate a change in concentration caused by a variation in the measurement of the analytical signal.

Qualitative vs. Quantitative Analysis

The science that studies the principles and techniques of chemical analysis. It is divided into:

• Qualitative analysis: Its purpose is the identification of the constituents of a sample (organic