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

Atomic Structure and Properties

Atomic Models

The concept of matter, initially considered indivisible according to Dalton, is presented with a discontinuous structure based on cathode rays (Thomson) and canal rays (Goldstein).

Rutherford considered the atom to consist of a small, hard core containing protons and neutrons, with electrons rotating around this core.

Bohr proposed that electrons in the atom are located in specific energy levels and sublevels, representing the distribution of electrons around the nucleus.

Key Atomic Definitions

Atomic Number (Z)

Atomic number (Z): Z = Number of Protons = Number of Electrons (in a neutral atom).

Mass Number (A)

Mass number (A): A = Number of Protons + Number of Neutrons.

Isotopes

Isotopes: Atoms of the same... Continue reading "Fundamental Chemistry Principles" »

Glass Manufacturing

Key Concepts in Glass Production

Glasses containing cuprous oxide have a red color.

The process used in the manufacture of glass is called continuous casting.

The most common fining agents used in glass manufacturing include nitrate and sodium antimony.

Opalescent substances commonly used in glass manufacturing include sodium silicate, cryolite, and calcium fluoride.

In glassmaking, soda ash and sodium sulfate act as fluxes.

Modern glass consists of a mixture of calcium oxide, sodium carbonate, and silica.

Bleaching agents used in glass manufacturing include manganese dioxide and selenium.

Types of Substances Used in Glassmaking

Vitrifiers: These substances transition from a crystalline structure to an amorphous structure under the... Continue reading "Glass and Paper Manufacturing Processes & Chemical Industry Overview" »

Radioactivity

Radioactive substances are characterized by emitting radiation capable of penetrating bodies that are opaque, ionizing the air, impressing photographic plates, and exciting the fluorescence of certain substances.

Alpha, Beta, and Gamma Radiation

Radioactive nuclei emit α radiation (helium nuclei), β (fast electrons), or γ (electromagnetic waves more energetic than X-rays). These radiations are ordered by their penetrating power in this way: α, β, and γ (from least to most penetrating).

Radioactive Decay

Radioactive decay is a random process. The number of nuclei, N, which have not yet disintegrated at an instant of time t is given by:

N = N₀e^-λt

The half-life, T, is the time required to disintegrate half of the initial nuclei.... Continue reading "Radioactivity, Atomic Nucleus, and Nuclear Reactions" »

Metallic Material Classification

Metallic materials are classified in several ways:

• By chemical composition (e.g., steel or bronze).
• By use (e.g., light-alloy steel, light alloys).
• By manufacturing process (e.g., sintered materials).
• By main applications (e.g., for ships, plates).

Forms of Iron Materials

Iron can exist in various forms, including:

• Forged iron
• Cast iron
• Steel
• Conglomerate iron

Non-Ferrous Material Classification

Non-ferrous materials are classified into:

• Heavy Alloys: Copper, lead, zinc.
• Light Alloys: Aluminum, titanium.
• Ultra-Light Alloys: Magnesium, beryllium.

The Catalan Forging Process

The Catalan forging process utilized a small furnace or fireplace where wood or charcoal combustion was alternated with iron ore. Combustion, enhanced by air... Continue reading "Metallic Materials: Classification, Iron, Steel, and Casting" »

Zinc Concentrate Roasting Process: 850 T/day Capacity

Blende-Roasting Furnace and Heat Recovery Steam Generator

This includes the furnace that carries out the oxidation of ZnS, the heat recovery steam generator for cooling the gas, and the partial removal of solids carried by the gases.

Treatment Water for Steam-Water Circuit

This is the demineralized process water. This water will be used in the heat recovery boiler and furnace beams, which form part of the same circuit.

Purification of Gases from Roasting

The functions of the gas produced are to eliminate impurities and reduce the gas temperature for treatment.

Contact and Absorption

This is the transformation of SO₂ into sulfuric acid for reuse in marketing or the leaching stage.

Feedstock and Products

This... Continue reading "Zinc Concentrate Roasting Process in a Fluidized Bed Furnace" »

Chlorides

Chlorine, as an element, has a huge tendency to form the chloride ion (Cl^-, a chlorine atom with a negative charge). This ion, in turn, will tend to form salts with other positively charged elements or cations (Na⁺ sodium, K⁺ potassium, Mg²⁺ magnesium, etc.). The chloride ion is one of the main inorganic anions in natural water and wastewater. The chloride content of water is variable and is mainly due to the nature of the terrain traversed. Typically, the chloride ion content of natural waters is less than 50 mg/L. In drinking water, the salt produced by the Cl^- is variable and depends on the water chemistry.

Chlorite and Chlorate

These are salts derived from chloric acid and chlorous acid. These compounds tend to form chlorine gas,... Continue reading "Chloride: Properties, Uses, and Health Effects" »

Ranking Elements

The first classification of chemical elements was based on their chemical and physical properties, dividing them into two large groups: metals and non-metals.

• The first classification was done by J.W. Döbereiner. He observed a link between the atomic mass and properties of elements such as barium, calcium, and strontium. He arranged 40 elements in a line, one after another, by their mass.
• John Newlands arranged the elements by atomic mass, from the lowest to the highest, in columns. This is now called the Law of Octaves.
• D.I. Mendeleev arranged the elements by atomic mass. As a result of this work, the periodic law of elements was discovered in 1869.

Forces Between Molecules

These are listed from weakest to strongest:

1. Dispersion

Reactions in Aqueous Solutions

Acid and Base Definition According to Bronsted-Lowry

Acid: A substance capable of donating protons.

Base: A substance capable of accepting protons.

For a substance to act as an acid, it must be in the presence of another substance that acts as a base and accepts the proton transferred by the acid. In aqueous solutions, water plays the role of both acid and base.

• When an acid donates protons, it becomes a species capable of accepting protons, called the conjugate base.
• When a base accepts protons, it is transformed into a species capable of donating protons, i.e., an acid, called the conjugate acid.

Equilibrium of Water Dissociation and the Concept of Kw

Water behaves as both an acid and a base according to the reaction:... Continue reading "Chemical Reactions in Aqueous Solutions and Stoichiometry" »

Chemical Bonding

Introduction

Chemical bonds are the forces that hold atoms together, leading to the formation of molecules and crystals. There are three primary types of chemical bonds:

1. Ionic Bonds

Ionic bonds occur between a metal and a nonmetal. In this type of bond, one atom loses electrons (forming a positive ion called a cation) while the other gains electrons (forming a negative ion called an anion).

2. Covalent Bonds

Covalent bonds form between two nonmetals. Atoms in a covalent bond share electrons to achieve a stable electron configuration. Each shared pair of electrons represents a covalent bond. These bonds can be visualized using Lewis diagrams.

3. Metallic Bonds

Metallic bonds occur between atoms of the same metal. In metallic bonding,... Continue reading "Understanding Chemical Bonds: A Comprehensive Look" »

Acid-Base Reactions

Acid-base reactions are essential in chemistry, allowing us to determine the concentration of an acid or base solution through titration. This process involves using a solution of known concentration (a standard solution) and an acid-base indicator.

Neutralization

Neutralization is the combination of hydrogen ions (H⁺) and hydroxide ions (OH^-) to form water (H₂O) and a salt. These reactions are exothermic, meaning they release heat.

Acid + Base → Salt + Water

Titration of a Strong Acid with a Strong Base

When titrating a strong acid (e.g., hydrochloric acid, HCl) with a strong base (e.g., sodium hydroxide, NaOH), the reaction is a straightforward neutralization:

HCl + NaOH → NaCl + H₂O

Titration of a Weak Acid with a Weak Base

Titrating... Continue reading "Acid-Base Reactions: Titration, Neutralization, and Indicators" »