Class 11 Engineering Chemistry - Some P-Block Elements

What are silicones? How are they prepared?

Silicones-They are a group of organosilicon polymers, which have (

R_{2} S i O

$R_2SiO$ ) as a repeating unit. Preparation of Silicones-The starting materials for the manufacture of silicones are alkyl or aryl substituted silicon chlorides

R_{n} S i C I_{4 - n}

$R_nSiCI_{4-n}$ , where

R

$R$ is alkyl or aryl group.

When methyl chloride reacts with silicon in the presence of copper as a catalyst at a temperature

570 K

$570 \ K$ , various types of methyl substituted chlorosilanes are formed. Hydrolysis of dimethyl dichloro silane i. e.,

(C H_{3})_{2} S i C l_{2}

$(CH_3)_2 SiCl_2$ followed by condensation polymerisation forms straight chain polymer i. e., silicone.
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Write the formula of unit of Silicones.

Silicones are a group of organosilicon polymers which have (

R_{2} S i O

$R_2SiO$ ) as a repeating unit.

If the starting material for the manufacture of silicones is $RSiCl_3$ , write the structure of the product formed.

The structure of product formed is as shown.

Answer the following:
Name one silicate and one phosphate ore of lithium.

Lepidolite (silicate ore) Triphylite (phosphate ore)

Triphylite is a lithium iron(II) phosphate mineral with the chemical formula

L i F e P O_{4}

$LiFePO_4$ .

Explain why the silicate oliving $(FeMg)_2SiO_4$ does not follow the law of constant composition.

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Classify the following silicates:
Beryl

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Classify the following silicates:
Feldspar

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(a)What are silicones? State the uses of silicones.
(b)What are boranes? Give chemical equation for the preaparation of diborane

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Classify the following silicates:
Zircon

Zircon is a mineral which is belong to the group of Nesosilicates.

It's chemical name is zirconium silicate and it's chemical formula

Z r S i O_{4}

$ZrSiO_{4}$ .

Zircon forms in silicate melts with large proportions of high field strength incompatible elements.

The natural colour of zircon varies between colourless, yellow golden , red brown, blue and green.

Silicon has become a vital element in the modern electronics industry. Why?

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In the following reactions assign for underlined atom for product of complete hydrolysis at R.T.
A. If product is oxy acid with —ic suffix.
B. If product is oxy acid with —ous suffix.
C. If product are two oxy acids one with —ic suffix and another one with —ous suffix.
D. If product is not oxy acid, neither with —ic suffix nor with —ous suffix.
$\underline SiCl_4+H_2O \longrightarrow H_4SiO_4+HCl$

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In the following reactions assign for underlined atom for product of complete hydrolysis at R.T.
A. If product is oxy acid with ic suffix.
B. If product is oxy acid with ous suffix.
C. If product are two oxy acids one with ic suffix and otherone with ous suffix.
D. If product is not oxy acid, neither with ic suffix nor with ous suffix.
$\underline SiH_4+H_2O \longrightarrow H_4SiO_4+H_2$

In this given reaction:

S i H_{4} 2 + H_{2} O \to H_{4} S i O_{4} + H_{2}

$SiH_42+H_2O\rightarrow H_4SiO_4+H_2$

Underline atom is

S i

$Si$ silicon belongs to carbon family i.e

14^{t h}

$14^{th}$ group

Since there is

1

$1$ oxy acids formed with suffix ic, which is

H_{4} S i O_{4}

$H_4SiO_4$ .

H_{4} S i O_{4}

$H_4SiO_4$ =silicic acid

Hence option A is correct answer

In the following reactions assign for underlined atom for product of complete hydrolysis at R.T.
A. If product is oxy acid with —ic suffix.
B. If product is oxy acid with —ous suffix.
C. If product are two oxy acids one with —ic suffix and another one with —ous suffix.
D. If product is not oxy acid, neither with —ic suffix nor with —ous suffix.
$H_6\underline {Si}O_7+H_2O \longrightarrow H_4SiO_4$

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How are linear silicones obtained?

Linear silicones are obtained by hydrolysis of

R_{2} S i C l_{2}

$R_2SiCl_2$ (chlorosilanes).

What is general formula of silicones?

[R_{2} S i O]_{n}

$[R_2SiO]_n$ is general formula of silicones.

What are silicones?

A silicone or polysiloxane are polymers made up of siloxane. They are typically colorless, oils or rubber-like substances

$HF$ can be stored in a glass vessel.
If true enter 1, else enter 0.

H F

$HF$ cannot be stored in glass vessels.

This is because

H F

$HF$ attacks silicates of glass.

4 H F + S i O_{2} \to S i F + 4 H_{2} O

$4HF+SiO_2\rightarrow SiF +4H_2O$

Therefore, the given statement is false and the correct entry is 0.

The organic solvent acetone has the molecular formula $(CH_3)_2CO$ . The silicon analogue, a thermally stable lubricant, is a polymer, $[(CH_3)_2SiO]_n$ . Account for the difference in structure.

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The value of $n$ in the molecular formula, $Be_nAl_2Si_6O_{18}$ is :

The value of

n

$n$ in the molecular formula,

B e_{n} A l_{2} S i_{6} O_{18}

$Be_nAl_2Si_6O_{18}$ is

3

$3$ .
The name of the compound is Beryl. It is ring silicate in which two oxygen atoms are shared per tetrahedron.

Fill in the blanks:

The hydrolysis of trialkyl chlorosilane, $R_3 SiCl$ , yields ______.

In the case of trimethylsilyl chloride, the hydrolyzed product is hexamethyl disiloxane:

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Write short notes on silicones.

Silicones are synthetic polymers with a silicon-oxygen backbone similar to that in silicon dioxide (silica), but with organic groups attached to the silicon atoms by

C - S i

$C-Si$ bonds. The silicone chain exposes organic groups to the outside.

The

S i - O

$Si-O$ bond energy is much larger than the

C - C

$C-C$ bond energy and this enables the

- S i - O -

$-Si-O-$ framework of the silicone to give the polymers thermal stability, as in silica, and so they can be used where comparable organic materials would melt or decompose

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Define:

Spodumene

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Sillicon has same valence electrons like carbon but it do not show the property similar to carbon, why?

The size of sillicon atom is larger than that of carbon atom causing a reduced force of attraction between electorns and the nucleus. In other words , the compounds formed by sillicon are very reactive whereas the compounds formed by the carbon are very stable . That is why sillicon does not exhibit the property similar to carbon .

What are silicates?

Silicates are minerals which consist of

S i O_{4}^{4 -}

$SiO_{4}^{4-}$ units arranged in different ways.

Some P-Block Elements - Class 11 Engineering Chemistry - Extra Questions