In the very broadest sense, inorganic chemicals and compounds are defined by what they are not; they are not organic in nature, such that anything beyond biological, hydrocarbon, and other similar carbon-based chemicals may be considered inorganic. From a practical standpoint, inorganic chemicals are substances of mineral origin that do not contain carbon in their molecular structure and are typically based on the most abundant chemicals on earth: oxygen, silicon, aluminum, iron, calcium, sodium, potassium and magnesium.

The top 20 inorganic chemicals manufactured in Canada, China, Europe, India, Japan, and the US (2005 data) are:

All of these chemicals and compounds have application in every aspect of the chemical industry-including catalysts, pigments, surfactants, coatings, medicine, fuel, and agriculture. The industry's products are used as basic chemicals for industrial processes (e.g., acids, bases, salts, oxidizing agents, gases, halogens), chemical additives (pigments, alkali metals, colors), and finished products (fertilizers, glass, construction materials).

The Inorganic Chemicals Industry

From an industry perspective, there are two main classes of inorganic chemicals: Alkali Chemicals (including soda ash, caustic soda and Liquid Chlorine) and Basic Inorganic Compounds (Aluminum Fluoride, Calcium Carbide, Potassium Chlorate, Titanium Dioxide, etc.).

Alkali Chemicals

The Chlor-Alkali Industry is an enormous component of the world economy. In essence, salt water (brine, NaCl) is split through electrolysis to generate caustic soda (Sodium Hydroxide, NaOH), Chlorine gas (Cl2) and Hydrogen (H2) gas.

The cell reaction above is:

2NaCl + 2H₂O = Cl₂ + H₂ + 2NaOH

Chlorine (Cl₂) is produced at the positive electrode (anode); hydrogen (H₂) and Sodium Hydroxide (NaOH, caustic) are produced at the negative electrode (cathode). These three materials are feedstocks for the production of bleach, vinyls, and a host of other products, including Soda Ash (Sodium Carbonate, Na2CO3), as outlined here:

Chlorine Uses             Caustic Soda Uses

Basic Inorganic Compounds

Inorganic synthesis, the process of synthesizing inorganic chemical compounds, is used to produce many basic inorganic chemical compounds. For example, an inorganic pigment is a natural or synthetic metallic oxide, sulfide, or other salt that is calcined during processing at 1200°F to 2100°F (650°C to 1150°C). Inorganic pigments have outstanding heat-stability, light-stability, weather resistance, and migration resistance.

These compounds are widely used in many applications, including electroplating, dye and precision casting, alcohol distillation, and papermaking. Sulfur dioxide and sulfites are inorganic chemicals used as preservatives. Inorganic compounds are also used as feed additives, insecticides, wood preservatives, and antiseptics.

Types of Inorganic Compounds

There are a few key types (or groups) of inorganic compounds, including:

Bio-Inorganic Compounds - natural and synthetic compounds that include metallic elements bonded to proteins and other biological chemistries.

Cluster Compounds - ensembles of bound atoms. They are intermediate in size, typically larger than a molecule yet more defined than a bulk solid.

Coordination Compounds - compounds where the central ion, typically a transition metal, is surrounded by a group of anions or molecules.

Organo Metallics - compounds that include carbon atoms directly bonded to a metal ion.

Solid State - diverse class of compounds that are solid at standard temperature and pressure, and exhibit unique properties as semiconductors, etc.

Inorganic Reaction Chemistry

Most inorganic chemical reactions fall into four broad categories: combination reactions, decomposition reactions, single displacement reactions, and double displacement reactions.

Combination Reactions

Reactions where two substances combine to form a third substance. A simple example is two elements reacting to form a compound of the elements and is shown in the general form:

A + B ---> AB

Examples include:

2Na(s) + Cl2(g) -> 2NaCl(s)

8 Fe + S8 ---> 8 FeS

Decomposition Reactions

Reactions where a single compound reacts to give two or more substances. In order to decompose a compound, it is often necessary to increase the temperature. An example of a decomposition reaction is the decomposition of mercury (II) oxide into mercury and oxygen when the compound is heated. A compound can also decompose into a compound and an element, or two compounds.

Single Displacement Reactions

Reactions where one element trades places with another element in a compound. These reactions come in the general form of:

A + BC ---> AC + B

Examples include:

Magnesium replacing hydrogen in water to make magnesium hydroxide and hydrogen gas:

Mg + 2 H2O ---> Mg(OH)2 + H2

The production of silver crystals when a copper metal strip is dipped into silver nitrate:

Cu(s) + 2AgNO3 (aq) -> 2Ag (s) + Cu(NO3)2 (aq)

Double Displacement Reactions

Reactions where the anions and cations of two different molecules switch places to form two entirely different compounds. These reactions are in the general form:

AB + CD ---> AD + CB

An example is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate:

Pb(NO3)2 + 2 KI ---> PbI2 + 2 KNO3

A special kind of double displacement reaction takes place when an acid and base react with each other. The hydrogen ion in the acid reacts with the hydroxyl ion in the base causing the formation of water. Generally, the product of this reaction is some ionic salt and water:

HA + BOH ---> H2O + BA

An example is the reaction of hydrobromic acid (HBr) with sodium hydroxide:

HBr + NaOH ---> NaBr + H2O

Acids, Bases, and Salts

Many inorganic compounds are available as acids, bases, or salts. There are several key products and performance characteristics of note:

Inorganic Acids

All inorganic acids elevate the hydrogen concentration in an aqueous solution. Key products include:

• Carbonic Acid - a weak inorganic acid.
• Hydrochloric Acid (HCl) - a highly corrosive, strong inorganic acid with many uses.
• Hydrofluoric Acid (HF) - a weak inorganic acid that is highly reactive with silicate, glass, metals, and semi-metals.
• Nitric Acid (HNO3) - a highly corrosive and toxic strong inorganic acid.
• Oxalic Acid - a relatively strong inorganic acid commonly used in cleaning and bleaching applications.
• Phosphoric Acid - not considered a strong inorganic acid. It is found in solid form as a mineral and has many industrial uses.
• Sulfuric Acid - a highly corrosive inorganic acid. It is soluble in water and widely used.

Inorganic Bases

All inorganic bases elevate the hydroxide concentration in an aqueous solution

• Ammonium Hydroxide (Ammonia Water) - a solution of ammonia in water.
• Calcium Hydroxide (Lime Water) - a weak base with many industrial uses.
• Magnesium Hydroxide - referred to as brucite when found in its solid mineral form.
• Sodium Bicarbonate (Baking Soda) - a mild alkali.
• Sodium Hydroxide (Caustic Soda) - a strong inorganic base. It is widely used in industrial and laboratory environments.

Inorganic Salts

Inorganic salts are neutral, ionically-bound molecules and do not affect the concentration of hydrogen in an aqueous solution.

• Calcium Chloride - many industrial uses.
• Potassium Dichromate - commonly used as an oxidizing agent.
• Sodium Chloride - common table salt used in the food industry.

Inorganic Building Blocks

Inorganic compounds, in a broader sense, consist of an ionic component (an element from the Periodic Table shown below) and an anionic component. A very large number of compounds occur naturally while others may be synthesized. In all cases, charge neutrality of the compound is key to the structure and properties of the compound.

Ionic compounds may be produced from a combination of an ionic component and an anioinic component where stoichiometric and other rules are met. Ionic building blocks for such compounds include:

And, anionic components include:

Properties

Specifications for inorganic chemicals include synonyms, molecular weight, formula/structure, functional group, Chemical Abstract Service (CAS) registry number, occurrence, uses and applications, physical properties, methods of preparation with chemical equations, chemical reactions, and health chemical analysis.

Inorganic compounds may be classified based upon their properties, including:

• Material Form
  • Gas
  • Liquid (or a solution)
  • Colloid, emulsion or dispersion
  • Powder
  • Bulk solid (pellets, flakes, granules)
• Flash point is the lowest temperature at which a liquid can form an ignitable mixture in air near the surface of the liquid. The lower the flash point, the easier it is to ignite the material.
• Purity is the weight percent of the main component(s) such %Al2O3 for alumina ceramics.
• Concentration is the actual quantity of a chemical or compound present in a bulk solid, liquid or gas. It is expressed as a percentage.

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Chemical Engineering Labratory | Chemistry Land | Stephen Lower of Simon Fraser University | Electochemistry Encyclopedia | Science Prof Online |