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

Chemical Nomenclature Rules

This section outlines the basic rules for naming binary and ternary chemical compounds.

Binary Compounds

• Metal Oxides: Oxygen (O) typically has an oxidation state of -2. Formula: M_xO_y (M: metal).
  • Lower oxidation state suffix: -ous.
  • Higher oxidation state suffix: -ic.
• Non-metal Oxides: Oxygen (O) typically has an oxidation state of -2. Formula: NM_xO_y (NM: non-metal).
• Metal Hydrides: Hydrogen (H) has an oxidation state of -1. Formula: MH_x.
• Non-metal Hydrides: Hydrogen (H) has an oxidation state of +1. Formula: H_xNM.
  • Nomenclature term: hydrogen [non-metal root]-ide.
• Binary Acids (Hydrohalic Acids): Non-metal hydrides (often Group 16 or 17 elements) dissolved in water.
  • Nomenclature term: hydro-[non-metal root]-ic acid.
• Binary Salts:

... Continue reading "Chemical Nomenclature and Atomic Structure Fundamentals" »

Cytology Fixatives

Solution: Cytology fixatives, formerly employing ether/alcohol 96 in equal parts, are now rarely used due to the hazardous nature of ether. The 96% alcohol is most often used. The procedure involves immersing the preparation in the fixative bath for a minimum of 10 to 15 minutes. Other alcohols, such as 100% methanol, 80% propanol, and 80% isopropanol, can also be used. Citospray is used in samples obtained by forced exfoliation.

Sample Types in a Cytology Laboratory

Samples that can reach the lab from samples obtained by:

• Forced exfoliation: Rubbing or scraping with various instruments. This is applied to the skin and organs accessible from the outside.
• Spontaneous exfoliation: Samples containing spontaneously exfoliating

... Continue reading "Cytology Fixatives and Staining Techniques" »

Solubility Fundamentals

Definition of Solubility

Solubility: The maximum concentration of a solute in a saturated solution at a given temperature in a given solvent.

Factors Affecting Salt Solubility

• Temperature (Temp): Generally, higher temperatures increase solubility.
• Entropy: Highly soluble substances often exhibit high entropy (disorder); the reverse is true for less soluble substances.
• Ion Size: A greater size difference between ions typically leads to higher solubility.
• Charge Density: This is the ratio between the ion's charge and its size. Lower charge density results in higher solubility because the solvent can more easily overcome the electrostatic attraction between the ions of the compound.

Equilibrium Factors Affecting Solubility

• Common

... Continue reading "Chemical Solubility Principles and Electrolysis Reactions" »

Stoichiometry: Quantitative Chemical Relationships

In chemistry, stoichiometry (from the Greek "στοιχεῖον" = stoicheion (element) and "μέτρον" = metron (measure)) is the calculation of the quantitative relationships between reactants and products during a chemical reaction. These relationships can be deduced from atomic theory, although historically they were formulated without direct reference to the composition of matter, based on various laws and principles.

Molarity (Molar Concentration)

Molarity (M), or molar concentration, is the number of moles of solute per liter of solution. For example, if 0.5 mole of solute is dissolved in 1000 mL of solution, the concentration of that solute is 0.5 M (0.5 molar).

Molality

Molality (m)

... Continue reading "Stoichiometry Fundamentals: Chemical Calculations & Concentrations" »

Carbohydrates: Structure and Function

Monosaccharides

These are simple carbohydrates, often referred to as simple sugars. They are called sugars due to their sweet taste and are carbohydrates because they contain hydrogen and oxygen in the same proportion as water. Their general formula is (CH₂O)_n, where 'n' represents the number of carbon atoms, typically ranging from 3 to 7.

Depending on whether the carbonyl group is an aldehyde or a ketone, monosaccharides are classified as aldoses or ketoses, respectively. Based on the number of carbon atoms, they are further classified as:

• Trioses (3 carbons)
• Tetroses (4 carbons)
• Pentoses (5 carbons)
• Hexoses (6 carbons)
• Heptoses (7 carbons)

Their main functions are energy storage and structural support. Regarding... Continue reading "Carbohydrates and Lipids: Fundamental Biomolecules" »

Understanding the Atom: Fundamental Building Blocks

The atom is the smallest indivisible particle from which all matter is built. While all atoms are fundamental, they differ according to the specific element they constitute. Despite their small size, atoms contain several internal parts and particles. Historically, various models, such as those proposed by Thomson and Rutherford, attempted to explain atomic structure. We will focus on the most current and widely accepted model, the Bohr model.

The Atomic Nucleus: Protons and Neutrons

The central part of the atom is the nucleus, which contains two primary types of particles:

• Neutrons: Particles with no electric charge (charge = 0).
• Protons: Particles with a positive electric charge (charge = +1)

... Continue reading "Atomic Structure: Particles, Nucleus, Electrons, Isotopes" »

ZOE Impression Paste

Advantages: Good adhesion, adequate working time, requires no insulation to the plaster model, is fluid allowing copying of fine details, and is economical.

Disadvantages: The Eugenol is acidified, and some patients are allergic to eugenol.

Elastomers

Organic materials formed by weak interaction with polymer molecules, forming a three-dimensional network with elastic properties.

Mercaptan Elastomers

Elastic impression materials with mercaptan groups in the polymer chain, which when hardened, forms a semisolid paste.

Synonyms: Polysulphide rubber, synthetic rubber, tiocoles.

Commercial presentation: Pasta-pasta

Consistencies: Light, regular, heavy.

Chemical Composition:

Paste: Polysulfide polymer (base), titanium dioxide (filler) can... Continue reading "Dental Impression Materials: ZOE Paste & Elastomers" »

Mercaptan

Disadvantages: Unpleasant smell and color, can cause stains on clothing, requires a custom tray, prolonged polymerization time, slow elastic recovery in deep undercuts.

Condensation Silicones

Elastic impression materials based on polymethylsiloxane, hardened by a polymerization process in the presence of a catalytic reactor.

Chemical Composition

• Base: Polymethyl siloxane (base), silica (filler).
• Catalyst: Ortoalquilico silicate (reactor, crosslinking agent), tin octanoate (catalyst or accelerator), oily diluent (if liquid), thickening agent (if paste).

Chemical Reaction

Tin octanoate --- Polymethylsiloxane (base) + Ortoalquilico silicate (reactor) = Silicone + Alcohol

Secondary Product: Alcohol.

Commercial Presentation

Presentations: Pasta-... Continue reading "Silicone Impression Materials: Condensation and Addition Types" »

Classification of Elements by Common Oxidation States

The following lists categorize elements based on their typical oxidation states or group characteristics:

• +1 State: H, Li, Na, K, Rb, Cs, Fr, Zn, Ag, F
• +2 State: Be, Mg, Ca, Sr, Ba, Ra, Cd, O
• Variable States:
  • Mn: (+2, +7)
  • Fe, Ni, Co: (+2, +3) (Co assumed from Ci)
  • Cu, Hg: (+1, +2)
  • Pd, Pt, C, Si, Ge, Sn, Pb: (+2, +4)
  • Au: (+1, +3)
• Group 13 (+3 State): B, Al, Ga, In, Tl
• Group 15 (+3, +5 States): N, P, As, Sb, Bi
• Group 16 (-2, +4, +6 States): S, Se, Te, Po
• Group 17 Halogens (+1, +3, +5, +7 States): Cl, Br, I

Fundamental Periodic Trends

Ionization Energy (IE)

The minimum energy required to remove an electron from a gaseous atom in its ground state, forming a positive ion (cation). Trend: Increases moving right... Continue reading "Essential Concepts in Atomic Structure and Chemical Bonding" »

Commercial Gypsum Composition and Purity

The commercial gypsum composition is formed by a mixture of Hemihydrate (HH) and some anhydrous Dihydrate (DH) nuclei, besides the impurities brought from the quarry.

Chemical Composition and Proportions

The typical proportions are:

• Hemihydrate (HH): 20% to 70%
• Anhydrite: 80% to 90%

Sources of Gypsum Impurities

Once obtained, it is necessary to distinguish two types of impurities:

Raw Material Impurities

These come from the source materials. If the gypsum stone contains impurities, these impurities will transfer to the final product.

Manufacturing Process Defects

These are impurities or defects produced during the manufacturing process, such as under-calcined (incocidos) and over-calcined (overcooked) material.... Continue reading "Gypsum Composition, Hydration, and Metal Interaction in Construction" »