Silicon Dioxide

Silicon dioxide is not found as an independent natural material. Many people generally term it silica. As such, it is amazingly ubiquitous and will be capable of providing frameworks for thousands of both natural and synthetic products in modern times. It defines its elasticity in terms of properties, hence applicable to an extremely wide variety of materials—from everyday use to cutting-edge technologies.

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This Story also Contains

1. Explanation
2. Different Aspects and Types of Silicon Dioxide
3. Some Solved Examples

Explanation

It is a chemical compound with an empirical formula featuring one silicon atom bonded to two oxygen atoms. Otherwise, it is simply called silica. It is one of the most abundant materials available on Earth in quartz, sand, and even in living organisms. Basically, silicon dioxide represents the hard compound that provides complete chemical inertness. Due to such stability, it remains essentially imperative for geological formation and provides wide applications in several industrial processes.

95% of the earth’s crust is made up of silica and silicates. Silicon Dioxide, commonly known as silica, occurs in several crystallographic forms. Quartz, cristobalite, and tridymite are some of the crystalline forms of silica, and they are interconvertible at suitable temperatures. Silicon dioxide is a covalent, three-dimensional network solid in which each silicon atom is covalently bonded in a tetrahedral manner to four oxygen atoms. Each oxygen atom in turn covalently bonded to other silicon atoms as shown in the figure. Each corner is shared with another tetrahedron. The entire crystal may be considered a giant molecule in which eight-membered rings are formed with alternate silicon and oxygen atoms.

Silica in its normal form is almost non-reactive because of very high Si—O bond enthalpy. It resists the attack by halogens, dihydrogen, and most of the acids and metals even at elevated temperatures. However, it is attacked by HF and NaOH.

SiO2+2NaOH→Na2SiO3+H2OSiO2+4HF→SiF4+2H2O

Quartz is extensively used as a piezoelectric material; it has made it possible to develop extremely accurate clocks, modern radio and television broadcasting, and mobile radio communications. Silica gel is used as a drying agent and as a support for chromatographic materials and catalysts. Kieselghur, an amorphous form of silica is used in filtration plants.

Different Aspects and Types of Silicon Dioxide

It can take forms that may well pluralize their properties and uses. Their common ones are crystalline and amorphous silica. The atomic structure of silica, as in quartz, and crystalline, gives it extraordinary strength and is the basic raw material used for making glass, ceramics, and cement. While crystalline silica exhibits an ordered atomic structure, amorphous silica does not; hence its properties differ substantially. That includes other uses that extend into applications such as a flow agent in pharmaceuticals and food products. Also, most synthetic forms of silica, such as fumed silica, find an application in rubber reinforcing and other applications like coatings and adhesives due to the fine particulate nature of such synthetic forms of silica.

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Some Solved Examples

Example 1
Question:
Silica in its normal form is almost non-reactive because of:
1) Very low Si-O bond enthalpy
2) Very high Si-O bond enthalpy
3) Oxide layer formation on its surface
4) It is a non-metallic compound

Solution:
Silica (SiO₂) has a network structure. It is almost inert because of the very high bond enthalpy of the Si-O bond.

Hence, the correct answer is Option (2).

Example 2
Question:
The amorphous form of silica is:
1) Tridymite
2) Kieselguhr
3) Cristobalite
4) Quartz

Solution:
Quartz, Tridymite, and Cristobalite are crystalline forms, and Kieselguhr is an amorphous form of silica.

Hence, the correct answer is Option (2).

Example 3
Question:
Silica can react with:
1) HF but not with NaOH
2) NaOH but not with HF
3) both NaOH as well as HF
4) neither NaOH nor HF

Solution:
Silica has a very high Si-O bond enthalpy and is almost non-reactive. However, it is attacked by HF and NaOH. The reactions are given below:

SiO2+2NaOH→Na2SiO3+H2O

SiO2+4HF→SiF4+2H2O

Hence, the correct answer is Option (3).

Summary

This compound is versatile, and basic, and is even abundantly available in nature and, therefore, much used in a number of industries. Naturally, this stretches from the sand lying on beaches to screens used on smartphones, which are huge, thereby underlining the necessity of the compound for both the banal and high-tech. The resiliency and variability of silicon dioxide have made it an essential base both for modern materials science and industry.