Silicates and Silicones Overview

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Questions and Answers

What is the ionic radius of Al+3 in tetrahedral coordination?

0.26 Å

0.39 Å (correct)

0.54 Å

1.36 Å

Feldspars, zeolites, and ultramarines are classified under which group of minerals?

Inosilicates

Phyllosilicates

Nesosilicates

Tectosilicates (correct)

Which of the following is a main component of Portland cement?

SiO2 (correct)

Al2O3

MgO

Fe2O3

What type of materials are aluminosilicates when they are supercooled?

Isotropic amorphous Signup and view all the answers

What transformation occurs when calcium hydroxides convert in cement?

Convert to carbonates Signup and view all the answers

Which statement about zeolite applications is incorrect?

Used solely in agriculture Signup and view all the answers

What unique property do borosilicate glasses possess?

High heat resistance Signup and view all the answers

Who coined the term 'silicone'?

J Stanley Kipping Signup and view all the answers

What was Kipping's initial description of the products he obtained from silicone polymer synthesis?

Sticky messes of no particular use Signup and view all the answers

Which of the following methods is considered an economically viable alternative to the Grignard method for synthesizing organochlorosilanes?

Rochow-Mueller Process Signup and view all the answers

Which type of silicone polymer is characterized by a three-dimensional structure?

Cross-linked silicone Signup and view all the answers

What is the end product of the hydrolysis of SiCl4?

Silica (SiO2) Signup and view all the answers

What is the result of the reaction where Me2SiCl2 undergoes hydrolysis?

Generation of silanol compounds Signup and view all the answers

What is the basic building block of all silicate minerals?

[SiO4]4− tetrahedron Signup and view all the answers

Which statement correctly describes the bond character in Si—O bonds?

50% ionic and 50% covalent Signup and view all the answers

Why cannot soluble silicate be used with hard water?

It forms insoluble calcium silicate. Signup and view all the answers

What is the typical valence of the cations that partner with isolated (SiO4)4− tetrahedra in nesosilicates?

+2 Signup and view all the answers

What percentage of minerals in the Earth's crust are silicates?

<blockquote> 90% </blockquote> Signup and view all the answers

Which mineral is an example of a sorosilicate?

Hemimorphite Signup and view all the answers

What is the basic structural unit of the amphibole group of minerals?

Si4O11 Signup and view all the answers

What geometric shape does the [SiO4]4− tetrahedron take?

Tetrahedral Signup and view all the answers

Which of the following describes the structural formula for pyroxenes?

(SiO3)n2n- Signup and view all the answers

Which silicate group shares one of its corner oxygens with another tetrahedron?

Sorosilicates Signup and view all the answers

What percentage of all known minerals are classified as silicates?

27% Signup and view all the answers

Which mineral is the most important source of beryllium?

Spodumene Signup and view all the answers

Which statement correctly describes phyllosilicates?

They form infinite sheets with shared oxygens. Signup and view all the answers

Which of the following is a characteristic of tectosilicates?

Form a 3D framework where all oxygens are shared. Signup and view all the answers

What type of silicate structure does the mineral Talc represent?

Phyllosilicate Signup and view all the answers

What is the lowest glass transition temperature of silicone polymers?

-127 °C Signup and view all the answers

Which of the following is NOT a type of silicone polymer?

Silicone gels Signup and view all the answers

What property makes silicones suitable as low temperature lubricants?

Non-volatility Signup and view all the answers

Which catalyst can be used to produce silicone polymers?

Acid or base catalyst Signup and view all the answers

For what application are silicones used due to their high thermal stability?

High temperature applications Signup and view all the answers

What feature of silicone materials contributed to the success of the first human footprint on the moon?

Hydrophobicity Signup and view all the answers

Which of the following describes silicone rubbers?

Crosslinked silicone fluids Signup and view all the answers

What is one of the key benefits of using silicones in electric wiring?

Thermal resistance Signup and view all the answers

Study Notes

Silicon Compounds

Silicon differs from carbon in terms of structure and reactivity; SiO2 is a network solid, while CO2 is a gas.
SiCl4 reacts with water, whereas CCl4 does not, showcasing silicon's reactivity.
Silane alcohol dehydration results in polymers, non-analogous to carbon alkenes.

Silicates and Their Prevalence

Earth's crust predominantly consists of Oxygen (O) and Silicon (Si), with over 90% of minerals being silicates.
Silicates account for 27% of known minerals and 40% of common minerals.

Silicate Characteristics

Majority of silicates are insoluble due to their infinite polymeric structure and stable Si-O bonds.
The building block of silicates is the [SiO4]4− tetrahedron; silicon has a +4 oxidation state and oxygen -2.

Silicate Formation and Use

Soluble silicates can form by fusing metal carbonates with sand at high temperatures (1400°C).
Used in liquid detergents to maintain high pH but inefficient in hard water due to insoluble calcium silicate formation.

Silicate Structure Principles

Silicates exhibit an infinite ionic polymer structure with a Si-O bond that is 50% ionic and 50% covalent.
Silicon's ionic radius is 0.26 Å, while oxygen's is 1.36 Å, leading to an ionic Si:O radius ratio of 0.21.

Silicate Anions

Nesosilicates (Isolated Tetrahedra): Composed of X2(SiO4) units; examples include Olivine (Mg, Fe)SiO4.
Sorosilicates (Double Island): Sharing one oxygens forming Si2O7-6, e.g., Hemimorphite.
Cyclosilicates (Ring Silicates): Arranged in rings, formula (SiO3)n2n-, e.g., Beryl.
Inosilicates (Single/Dual Chain Silicates): Long chains of SiO4 linked by sharing oxygens, e.g., Pyroxenes, Amphiboles.
Phyllosilicates (Sheet Silicates): Forming infinite sheets with the basic unit Si2O5-2, e.g., Mica, Talc.
Tectosilicates (3D-Framework): All oxygens shared, forming a three-dimensional lattice, e.g., Quartz.

Role of Aluminum in Silicates

Aluminum can substitute silicon in silicate structures, leading to aluminosilicates and borosilicates.
Replacement of Si+4 with Al+3 introduces negative charges balanced by other cations.
Key groups include Feldspars, Zeolites, and Ultramarines.

Applications of Silicates

Cement: Mixture of Ca-silicates and aluminates; Portland Cement consists largely of CaO and SiO2.
Glass: Consists of aluminosilicates; can be molded and drawn into fibers. Borosilicate glass is especially heat-resistant.
Silica Gel: Used in chromatography.

Silicone Polymers

The term "silicone" was first coined by J Stanley Kipping in the early 1900s.
Silicones are strong, stable compounds widely utilized in fluids, elastomers, and resins.

Silicone Synthesis

Strong Si-C bonds; forms pπ-dπ bonds.
Prepared via Grignard reagents or organolithium compounds.
Rochow-Mueller Process is an economically viable production method for organochlorosilanes.

Properties and Uses of Silicones

Silicones are stable, non-volatile, and maintain low viscosity at high temperatures.
Used for insulation, low-temperature applications, and storing chemicals due to their high thermal and chemical stability.
Notably used in environments with extreme temperatures, such as the moon mission footwear.

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Description

Explore the unique properties of silicates and silicones in this quiz. Understand the distinctions between silicon compounds and their behaviors in different environments. Delve into the prevalence of silicate minerals in the Earth's crust and their significance in mineralogy.