Notes, summaries, assignments, exams, and exercises for Chemistry for Vocational training

Intermolecular Van der Waals Forces

Intermolecular Van der Waals forces are the forces that develop between the molecules of a covalent compound. These forces are far weaker than the chemical bonds themselves; they act by uniting various molecules, and their intensity depends mainly on the electronegativity difference between atoms forming the molecule and the size of the atoms. Consequently, the larger these factors are, the more intense the force between molecules will be.

Intermolecular forces are due to electrostatic attraction between permanent dipoles in heteronuclear molecules or induced dipoles in homonuclear molecules. The more intense the intermolecular forces, the greater the state of aggregation and the higher the melting and boiling

Methods of Water Purification

3. Ultraviolet (UV) Treatment

This method uses the appropriate wavelength to eliminate microorganisms and pathogens in water. UV light is more energetic than visible light and has a shorter wavelength. It is utilized for wastewater treatment with biological loads, irrigation water, and drinking water purification.

4. Copper-Silver Ionization

Small amounts of copper and silver are used to destroy microorganisms. It is applied in cooling towers, boilers, and similar systems. Its advantages include:

• Does not disrupt pH levels
• Easy to install
• Simple water recovery in case of loss
• Low maintenance costs

5. Water Softening

Hard water can cause lime deposition, fouling, and increases the consumption of soaps and detergents while...

Selectivity in Chemical Analysis

A reaction used in chemical analysis is selective when the reaction is characteristic of few substances, showing a preference for some of these. When the reaction is carried out only on a particular substance, it is specific.

Limit of Detection (LOD)

Refers to the minimum amount of a substance that can be detected in a trial.

Sensitivity of Analytical Methods

The ability of a method to discriminate a change in concentration caused by a variation in the measurement of the analytical signal.

Qualitative vs. Quantitative Analysis

The science that studies the principles and techniques of chemical analysis. It is divided into:

• Qualitative analysis: Its purpose is the identification of the constituents of a sample (organic

Fire Protection

Fire protection is defined as the set of measures implemented to avoid or reduce damage and injuries caused by fires in the workplace. Employers are obligated to take appropriate measures to combat fires. This involves specific strategies to prevent ignition and stop the spread of flames, as well as establishing an emergency plan for rapid personnel evacuation. To be effective, these measures must be supported by regular fire extinguishing and evacuation drills.

Basic Concepts of Fire

To prevent or fight a fire, one must understand the fundamental concepts of combustion. A fire requires a reaction between an oxidizing agent, a fuel, and a heat source. These factors are graphically represented by the Fire Triangle. All three elements...

Physical and Chemical Changes in Matter

A physical change is a transformation that does not vary the nature of matter. Before and after the change, the matter is represented by the same chemical formula. A chemical change is a transformation in which the nature of matter varies. Before the change, the substance is represented by one chemical formula, and afterwards, by a different formula.

The Collision Theory of Reactions

Collision theory: Chemical reactions occur when molecules of reactants collide and break. Atoms that have been released are rearranged to form new molecules.

Measurement of Mass: The Mole

The mole: A mole of atoms is the amount of a chemical element that is equivalent to its atomic mass in grams. In the SI system, the mole is...