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

Alkenes: Structure, Reactions, and Synthesis

Hydrogenation of Alkenes

Hydrogenation of alkenes involves the addition of hydrogen across the double bond. This reaction requires a catalyst, such as nickel (Ni) or platinum (Pt), which facilitates the reaction without being consumed. High pressure and temperature conditions are often employed to achieve efficient hydrogenation.

Halogenation of Alkenes

Halogenation of alkenes is an electrophilic addition reaction where a halogen molecule (e.g., Br₂, Cl₂) adds across the double bond. This process often involves the formation of intermediate ions.

During halogenation, the electrophilic halogen attacks the electron-rich double bond, for example, in ethene. This initiates an internal movement of electrons,... Continue reading "Alkenes and Alkynes: Essential Organic Chemistry Reactions" »

Mineralogy

Mineralogy is the science that studies the physical and chemical properties of minerals.

Mineral Classifications

Primary Minerals

Primary minerals are minerals found in their original deposits. An example is pyrite (FeS₂), known for its gold-like color and luster.

Secondary Minerals

Secondary minerals form from chemical reactions involving primary minerals. Anglesite (PbSO₄) is a secondary mineral derived from the primary mineral galena (PbS).

Solid Structures

Crystalline Solids

Crystalline solids have particles arranged in an orderly and regular pattern in three dimensions, following a defined geometric structure.

Amorphous Solids

Amorphous solids have particles arranged randomly, similar to the structure of liquids, resulting in a shapeless... Continue reading "Introduction to Mineralogy and Mineral Properties" »

Electric Nature of Matter

Matter undergoes electric phenomena. It can be uncharged (neutral), positively charged, or negatively charged.

• Like charges repel, and opposite charges attract.
• A body is neutral when it has an equal number of positive and negative charges.
• A positively charged body has more positive charges than negative charges.
• A negatively charged body has more negative charges than positive charges.

Electric charge in various media, and the forces exerted between charges, are described by Coulomb's Law.

Coulomb's Law

The force (F) between two point charges (Q₁ and Q₂) is directly proportional to the product of the charges and inversely proportional to the square of the distance (D) between them.

F = k * (Q₁ * Q₂) / D²

Where:

• Q: Electric

Atomic Models

Dalton's Atomic Model

Dalton proposed that atoms are indivisible, compact spheres with specific weights, explaining chemical reactions. However, this model doesn't explain the electrical nature of matter.

Rutherford's Atomic Model

Rutherford's experiment involved firing positively charged alpha particles at a gold foil. Most particles passed through undeflected, some were diverted, and others bounced back, leading to a new understanding of atomic structure.

Chemical Bonds

Ionic Bonds

When a metal is in the presence of a non-metal, a transfer of electrons occurs, forming ions with opposite charges. These ions are held together by electrostatic attraction. The ionic bond forms between ions of opposite charges. Ionic valence refers to... Continue reading "Atomic Models, Chemical Bonds, and Scientific Method" »

Understanding Carbohydrates

Carbohydrates are biomolecules primarily composed of carbon, hydrogen, and oxygen. Their atoms are linked to alcohol groups (hydroxyl groups, -OH) and hydrogen atoms (-H). All carbohydrates contain a carbonyl group (C=O), which can be either an aldehyde group (-CHO) or a ketone group (-CO). Therefore, they can be defined as polyhydroxyaldehydes or polyhydroxyketones.

Classification of Carbohydrates

Carbohydrates are classified into several groups:

• Monosaccharides: Simple sugars made of single units.
• Oligosaccharides: Contain between 2 and 10 monosaccharide units.
• Polysaccharides: Formed by multiple repeating units of monosaccharides, further divided into:
  • Homopolysaccharides: Formed by the repetition of a single monomer.

Chemical Bonds and Properties

Ionic Bonds

Ionic bonds are characteristic of compounds formed between a metal and a non-metal. Metals form positive ions (cations), and non-metals form ion-accepting negative ions (anions).

Properties of Ionic Compounds

• Soluble in water
• Hard and fragile
• Have an ionic crystal structure

Covalent Bonds

Covalent bonds are seen in particles formed by atoms of non-metals, as is the case of diatomic gas molecules. Atoms share one or more pairs of electrons to complete their outer octet.

Properties of Covalent Compounds

• Do not conduct electric current
• Molecules of simple gases have covalent bonds
• Have atomic or molecular crystalline structure

Types of Covalent Bonds

• Polar Covalent
• Non-Polar Covalent
• Coordinate Covalent: Two electrons

Atomic Structure and Chemistry Fundamentals

Organic chemistry is the science of matter. All matter occupies space. Plasma is when atoms are in a high-temperature environment.

• Elements: A single type of atom that cannot be transformed into simpler substances.
• Compounds: Substances formed by different types of atoms combined in a constant ratio.
• Homogeneous: Has a single phase, and components are indistinguishable (H₂O + C₆H₁₂O₆). Can be separated by evaporation or distillation.
• Heterogeneous: Components can be distinguished from each other.
• Phase: A portion of matter with definite limits. Can be separated by filtering or decanting.

d = mass / volume

Prefixes: milli (m) - 10^-3 / micro (μ) - 10^-6 / nano (n) - 10^-9

1 kg = 1000 g and 1 dozen = 12 units

Temperature... Continue reading "Atomic Structure, Compounds, and Chemical Formulas" »

Matter: Core Properties, States, and Mixtures

Matter is anything that has mass and occupies volume. It is characterized by two types of properties:

Key Properties of Matter

• General properties: These are mass and volume.
• Specific properties: These are different in each material, so they serve to differentiate materials from each other and assign them different uses.

The Three States of Matter

Matter can occur in three states:

• Gas: A gas has no definite shape and spreads to fill its container. It can be compressed and expands greatly with temperature.
• Liquid: A liquid does not hold its own shape (it takes the shape of its container) but has a definite volume. It is not easily compressed and expands slightly with increasing temperature, although much

Binary Compounds

Binary Oxygen Compounds (Oxides)

Systematic Nomenclature

• Prefixes (mono-, di-, tri-, tetra-...) + oxide (element symbol).
• e.g., N₂O₅: Dinitrogen pentoxide.

Stock Nomenclature

• Oxide of (element) + (valence of element in Roman numerals).
• e.g., N₂O₅: Nitrogen(V) oxide.

Binary Hydrogen Compounds (Hydrides)

Metal Hydrides (Hydrogen + Metal)

Systematic Nomenclature

• Prefixes (mono-, di-, tri-, tetra-...) + hydride of (metal).
• e.g., CrH₃: Chromium trihydride.

Stock Nomenclature

• Hydride of (metal) + (valence of metal in Roman numerals).
• e.g., CrH₃: Chromium(III) hydride.

Volatile Hydrides (Hydrogen + Semimetal)

Systematic Nomenclature

• Prefixes (mono-, di-, tri-, tetra-...) + hydride of (semimetal).
• e.g., PH₃: Phosphorus trihydride.

Common Names

• Ammonia

Osmosis, Buffers, Colloids, and Carbohydrates

Osmosis: Osmosis occurs when two solutions with different ionic concentrations are separated by a semipermeable membrane that allows water to pass through but restricts the passage of ions. There are three types of solutions: isotonic, hypertonic, and hypotonic.

Buffer Systems

In organisms, buffer systems are crucial for maintaining a stable pH in fluids. These systems prevent abrupt pH changes. Buffers are based on the properties of weak acids, which do not dissociate completely. Within a specific pH range, they act as proton donors and acceptors, maintaining a constant pH within certain limits. Certain salts and corresponding acids balance the pH. For example, the HCO-3/H2CO3 (bicarbonate buffer)... Continue reading "Osmosis, Buffers, Colloids, and Carbohydrates: A Concise Review" »