Acids, Bases, Salts and Oxides in Chemistry
Acids
According to Arrhenius (1887), an acid is any substance that, in aqueous solution, releases solely H+ ions. An example is hydrochloric acid (HCl):
H+ + Cl–Some years later, in 1923, Brønsted and Lowry proposed the idea that an acid is a substance that can transfer protons (H+).
This latter definition generalized Arrhenius’ theory of acids. The Brønsted-Lowry theory also serves for non-aqueous solutions. The two theories are very similar in the definition of acid, but the Brønsted-Lowry
Read MoreMetal Surface Treatments and Corrosion Protection
Metal Surface Treatments
Nitriding
This surface hardening treatment increases corrosion resistance using ammonia gas in a high-temperature oven. Rapid cooling and subsequent annealing are performed.
Sulfinization
This treatment increases sulfur and nitrogen percentages in the steel’s surface layer.
Oxidation
Metals and alloys release electrons, increasing their oxidation state. A redox reaction occurs with another substance. All metals oxidize in dry, warm conditions, forming a compact, homogeneous,
Read MoreThermodynamics & Thermochemistry: A Comprehensive Guide
Thermodynamics and Thermochemistry
Introduction
Thermodynamics is the study of energy transformations, particularly those involving heat and work. Thermochemistry, a branch of thermodynamics, focuses on energy changes during chemical reactions, which is the main subject of this unit.
Thermodynamic Systems
A thermodynamic system is the specific part of the universe being studied. Its immediate environment is called the surroundings. Systems are classified as:
- Open: Exchange both matter and energy with
Primary Air Pollutants: Sources, Impacts, and Control
Primary Air Pollutants
Sulfur Dioxide (SO2)
Properties: Colorless gas, reactive, soluble, and has a pungent odor at higher concentrations.
Sources:
- Natural: Organic matter decomposition, volcanic eruptions.
- Anthropogenic: Industrial processes (fossil fuel combustion, refining, chemical manufacturing).
Fate: Oxidizes to form SO3, leading to acid rain through dry and wet deposition.
Nitrogen Oxides (NOx)
Properties: NO (nitric oxide) is colorless, odorless, and non-flammable. NO2 (nitrogen dioxide) is a reddish-
Read MoreRedox Reactions, Voltaic Cells, and Electrolysis
Redox Reactions
Oxidation and Reduction
Oxidation: The process of electron loss by a reductant. The reductant is the substance that contains the element whose oxidation number increases.
Reduction: The process of electron gain by an oxidant. The oxidant is the substance that contains the element whose oxidation number decreases.
- Oxidation: Process where an element’s oxidation number increases (loses electrons).
- Reduction: Process where an element’s oxidation number decreases (gains electrons).
Redox Reactions:
Read MoreChemical Bonding: An In-Depth Exploration of Ionic, Covalent, and Metallic Bonds
The Periodic Table and Element Classification
The arrangement of elements in the periodic table is based on their atomic number, a concept discovered by Henry Moseley through his study of X-ray spectra. This organization reflects the electronic configuration of each element, with periods representing the filling of electron energy levels. The first period holds two elements, the second and third contain eight each. While subsequent periods also fill ‘d’ and ‘f’ sublevels, these are energetically
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