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

The Dawn of Radioactivity

At the end of the nineteenth century, two astonishing discoveries in the field of physics sparked a scientific revolution: X-rays and radioactivity. While Henri Becquerel was studying fluorescence, Wilhelm Roentgen discovered X-rays. The source of this radiation lies in the nuclei of uranium atoms, which undergo a process of transformation or disintegration into other chemical elements, releasing large amounts of energy in the form of radioactive rays.

Nuclear Processes

• Nuclear Fission: The splitting of a heavy atomic nucleus into two intermediate nuclei.
• Nuclear Fusion: The combining of two atomic nuclei to form a heavier nucleus.

Marie Curie and her husband, Pierre Curie, discovered two new chemical elements—radium... Continue reading "Radioactivity and Quantum Physics: Core Concepts Explained" »

Fundamentals of Chemistry

Chemistry is the science that studies the composition, structure, and properties of matter, as well as the changes it undergoes during chemical reactions and its relationship with energy.

Defining Matter and Its Properties

Matter is anything that occupies space, has measurable energy, and is subject to change over time and interactions with measuring devices.

States of Matter

• Solid: If the kinetic energy is less than the potential energy.
• Liquid: If the kinetic and potential energy are approximately equal.
• Gas: If the kinetic energy is greater than the potential energy.
• Plasma: If the kinetic energy is such that the electrons have a positive total energy.

Chemical Elements and Atomic Structure

A Chemical Element is a type of... Continue reading "Essential Chemistry Definitions: Matter, Elements, and The Mole" »

Atomic Structure and Nuclear Reactions

1. Atomic Components: Protons, Neutrons, and Electrons

Protons, possessing positive charges, reside within the nucleus. Negatively charged electrons revolve around the nucleus. Electrons must orbit to avoid being drawn into the nucleus. However, a question remained: how do protons, all with the same positive charge, remain together in the nucleus without repelling each other? There must be something more, leading to the postulation of neutrons.

2. Mass Defect and Binding Energy

The mass difference is explained by the binding energy between nucleons (protons and neutrons). According to the theory of relativity, any energy corresponds to a mass, which explains the mass defect.

3. Types of Radiation: Alpha, Beta,

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