Physical and chemical properties of silica
Silica, called silicon dioxide (IV), has a diamond-like structure. That is, each silicon atom is attached to its neighboring atoms by an oxygen atom. Remember that this is a small part of a huge SiO2 structure that extends in all three dimensions.
Physical properties
Silicon dioxide is gray, crystalline, odorless, or a clear, amorphous solid. Its melting and boiling points are 1713 ° C and 2950 ° C, respectively. Its density is about 2.648 grams per cubic centimeter. The compound is insoluble in both acid and water and soluble in hydrofluoric acid. Its molecular weight is about 60.08 grams per mole.
chemical properties
Silicon dioxide is not a reactive compound because its molecule polarity is zero because silica forms two double bonds with oxygen. So a molecule is very stable. In addition, it has a high dielectric strength, so it is used as insulation and semiconductor.
What is silica and what do you know about its uses?
Types of silica
Although sand and quartz crystals may look different, they are both primarily made of silicon dioxide. The chemical composition of these types is exactly the same and their properties are generally the same, but they are formed under different conditions. The sand particles are very small but rigid.
Some quartz crystals have a milky white appearance. The so-called milky quartz is very abundant, so it is common to find large stones of this type of quartz. Mineral impurities can turn purple, light pink, or other colors, resulting in the following gemstones or semi-precious stones:
Amethyst
Citrine
Quartz Rose
Smoky quartz
Silicon dioxide is found almost everywhere in the world because it is the most common mineral in the earth’s crust. This mineral can be found immediately on the surface of the earth, in rocky or mountainous areas. It is also found in the deserts and beaches of the world in the form of sand.
Silica production method
Further, silicon dioxide is obtained through mining activities including sand extraction and quartz refining. Quartz is suitable for many purposes, while chemical processing is required to purify another product (e.g., more reactive or fine-grained). Silica vapor is derived from hot processes such as ferrosilicon processing as a by-product.
In addition, acidification of sodium silicate solutions forms silica or amorphous silica deposits. The gel is washed and dehydrated to produce fine colorless silica. The reaction for trisilicate with sulfuric acid is given below.
Na2Si3O7 + H2SO4 → 3SiO2 + Na2SO4 + H2O
Silica reactions
Silica is converted to silicon by reducing carbon. When fluorine reacts with silicon dioxide it produces O2 and SiF4. Silicon dioxide also reacts with hydrofluoric acid to form hexafluorosilicic acid (H2SiF6).
SiO2 + 6HF → H2SiF6 + 2H2O
Method of preparation of silica
Silica is mostly extracted from the quartz mine, it can also be prepared by acid neutralizing an alkaline-silicate aqueous solution. This method is known as the wet process and forms amorphous SiO2 particles.
Na2Si3O7 + H2SO4 -> 3 SiO2 + Na2SO4 + H2O
Other methods form pyrogenic silica, which contains silane combustion such as silicon tetrachloride in an oxygen-hydrogen burner. The product of this reaction are fine silica particles with a diameter of 100-400 nm.
SiCl4 + 2H2 + O2-> SiO2 + 4 HCl