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

Key Chemical Thermodynamics Principles

First Law of Thermodynamics

Internal energy is equal to the heat released or absorbed by the system plus the work done by or on the system.

Standard Enthalpy of Formation

The heat change resulting from the formation of one mole of a compound from its elements in their most stable states of aggregation.

Enthalpy of a Chemical Reaction

The heat absorbed or released from the system when the reaction occurs at constant pressure.

Hess's Law

A chemical reaction can be expressed as an algebraic sum of others; its heat of reaction is equal to the algebraic sum of the heats of the partial reactions.

Bond Enthalpy (Bond Energy)

The heat flow, absolute, for the formation or rupture of a mole of bonds from the isolated atoms... Continue reading "Key Chemical Thermodynamics Principles Explained" »

Atomic Theory Evolution

John Dalton proposed that matter is composed of distinct masses that combine to form different compounds. He defined the atom as an indivisible and indestructible particle.

J.J. Thomson discovered the electron and defined the atom as a sphere with a positive charge, where negatively charged electrons were distributed.

E. Rutherford discovered that the atom consisted of a dense nucleus formed by protons with a positive charge, where electrons revolve around it with a negative charge.

Niels Bohr advanced Rutherford's model and discovered that electrons are found in orderly orbits.

Subatomic Particles

• Proton: A subatomic particle with a positive charge and a mass of 1.6726231 × 10^-27 kg.
• Neutron: A subatomic particle with no

Module 1: Science and Education

1. What is Science?

Science is the organized knowledge of our physical world, which encompasses everything we perceive through our five senses.

2. What is the Physical World?

The physical world relates to everything we interact with using our five senses.

3. Pillars of Science

The pillars of science are observation and reasoning.

4. Modus Operandi of Science

1. Accumulation of observed facts and a detailed description of what has been witnessed.
2. Generalization of these facts into laws, which can be represented by formulas, verbal statements, or other means of summarizing the observed events.
3. Explanation of facts through hypotheses and theories.
4. Drawing inferences from these assumptions and comparing them with experimental

Dalton's atomic theory: The matter is made up of extremely small particles, indivisible and indestructible called atoms. / Each chemical element has all different but identical atoms of other elements quimics. / Dalton Based on the chemical compound is formed by the union of atoms of different elements always the same type and the same proportion. Chemical Element: A substance that can not be decomposed into other more simple because it consists of a single type of atom. Compost: A substance that can be decomposed into others are made easier since most pet atoms of element types. Plum pudding model: the atoms are formed by electrons with negative charge are distributed in a sphere of matter of positive charge so that the overall atom is electrically... Continue reading "Atomic Structure and Nuclear Reactions: Key Concepts" »

Nuclear Fusion

Nuclear fusion is a reaction in which two light nuclei combine to form a heavier one. This process releases energy because the weight of the heavier nucleus is less than the sum of the weights of the lighter nuclei. This mass defect is converted to energy, as related by the formula E = mc². Although the mass defect is very small, and the gain per atom is also very small, it must be borne in mind that energy is very concentrated; a small amount of fuel yields a large amount of energy.

Not all fusion reactions produce the same energy; it always depends on the nuclei that bind and the reaction products. The easiest reaction to achieve is the fusion of deuterium (one proton plus one neutron) and tritium (one proton and two neutrons)... Continue reading "Nuclear Reactions: Fission, Fusion, and Radioactivity" »

Fundamentals of Electrolysis

Electrolysis is the process in which the passage of electric current through a solution or a molten electrolyte produces a non-spontaneous oxidation-reduction (redox) reaction.

Key Components of an Electrolytic Cell

The electrolytic cell (or container) is the vessel where the process takes place. It holds the solution or molten electrolyte, in which the electrodes are immersed and connected to a continuous (DC) power source.

The electrodes are the surfaces where the oxidation-reduction half-reactions occur. They tend to be inert. Electrodes are distinguished as follows:

• Cathode: The electrode where reduction occurs. In an electrolytic cell, it connects to the negative pole of the power source.
• Anode: The electrode where

Chemical Bonding and Molecular Structure

• • Ionic Compound: A chemical substance composed of positive and negative ions.
  • Crystal: A solid with flat faces that form sharp angles, whose atoms, ions, or molecules are arranged in a regular three-dimensional arrangement.
  • Double Bond: A covalent bond in which two pairs of electrons are shared between two atoms.
  • Electronegativity: The attraction an atom in a molecule exerts on the electrons of a covalent bond.
  • Electronegative Element: Elements, particularly fluorine, oxygen, and nitrogen, have a very strong attraction for the electrons involved in chemical bonding.
  • Covalent Bond: An electron pair shared between two atoms in a molecule.
  • Nonpolar Covalent Bond: A chemical bond in which one or more pairs of electrons

Understanding Atoms and Subatomic Particles

All matter consists of particles called atoms. An atom is composed of smaller elements known as subatomic particles:

• Protons: Possess a positive electric charge and are located in the nucleus.
• Neutrons: Carry no electric charge and are located in the nucleus alongside protons.
• Electrons: Carry a negative electrical charge and orbit in the electron cloud.

Dalton's Atomic Theory

In 1808, John Dalton retrieved the atomic theory of Democritus. He proposed that atoms were indivisible particles and the ultimate constituents of matter that combined to form compounds.

The Plum Pudding Model

Experiments conducted in 1897 on the conduction of electricity through gases led to the discovery of the negatively charged... Continue reading "Atomic Structure and Evolution of Atomic Models" »

Literary Analysis of Carmen Laforet's Themes

The Initiation Novel in Laforet's Work

The initiation novel, starring a girl who faces adult life, is a narrative subgenre that has had important development. In the novels of Carmen Laforet, there are frequent references to life experiences. Nada has all the components of the novel of initiation, but the transition to young adulthood and the resolution of the crisis do not occur through direct experience, but through the assumption of a foreign experience.

Yearning for Liberation and Change of Place

In all the works of Carmen Laforet, there is a yearning for liberation, a search for a new life that is always associated with a life-changing shift in location.

In the narrative, Andrea travels to Barcelona... Continue reading "Literary Themes and Lexical Renewal: Analyzing Laforet's Work" »

Concept of Solubility

Saturation Solubility

When the concentration of ions in the solution reaches a point where they tend to deposit (crystallize), an **equilibrium** ($K$) is reached between the process of dissolution and crystallization. Under these conditions, the solution is called **saturated**. The solubility of a solute is defined as the concentration of the solute in a saturated solution.

Influence of Temperature on Solubility

Most frequently, the solubility of an ionic solid in water increases with temperature.

Factors Affecting Solute Solubility

The solubility of different ionic substances in water varies significantly due to two primary factors:

• Crystal Stability: Very stable crystals are more difficult to dissolve. Crystals containing