Silica is not an acidic oxide.


Introduction:

The corresponding hydrate is silicic acid (H2SiO3). Silica is insoluble in water and acid, but soluble in hydrofluoric acid and hot concentrated phosphoric acid. It can act with molten bases. There are crystalline silica and amorphous silica in nature. Silica is widely used, mainly in the manufacture of glass, water glass, pottery, enamel and refractory materials.


physical property:

Silicon dioxide, also known as silica, has the chemical formula SiO ν. There are crystalline silica and amorphous silica in nature. Crystalline silica can be divided into quartz, scaly quartz and cristobalite due to different crystal structures. Pure quartz is colorless crystal. Large and transparent prismatic quartz is called crystal. If the crystal containing trace impurities has different colors, there are Amethyst, tea crystal, ink crystal, etc. Ordinary sand is fine quartz crystal, including yellow sand (more iron impurities) and white sand (less impurities and purer). In the silica crystal, the four valence electrons of the silicon atom form four covalent bonds with four oxygen atoms. The silicon atom is located in the center of the regular tetrahedron, and the four oxygen atoms are located at the four top angles of the regular tetrahedron. SiO ν is the simplest formula for composition, which only represents the ratio of the number of silicon and oxygen atoms in the silica crystal. Silica is an atomic crystal.

Diatomite existing in nature is amorphous silica, which is the remains of lower aquatic plant diatom. It is a white solid or powder, porous, light and soft solid with strong adsorption.


chemical property:

The chemical properties are relatively stable. It is insoluble in water and does not react with water. It is an acidic oxide and does not react with general acids. Gaseous hydrogen fluoride reacts with silicon dioxide to form gaseous silicon tetrafluoride. React with hot concentrated strong alkali solution or molten alkali to form silicate and water. It reacts with a variety of metal oxides at high temperature to form silicate. Used for manufacturing quartz glass, optical instruments, chemical utensils, ordinary glass, refractory, optical fiber, ceramics, etc. The nature of silica is inactive. It does not interact with halogen, hydrogen halide, sulfuric acid, nitric acid and perchloric acid other than fluorine and hydrogen fluoride (except hot concentrated phosphoric acid). Common concentrated phosphoric acid (or pyrophosphoric acid) can corrode silicon dioxide and generate heteropoly acid at high temperature. Molten borate or boronic anhydride can also corrode silicon dioxide at high temperature. In view of this property, borate can be used as flux in ceramic firing. In addition, hydrogen fluoride can also dissolve the acid of silicon dioxide to generate water-soluble fluorosilicic acid: 6HF + SiO З = h З SIF З + 2H З o