P-Block Flashcards

Question

On heating borax

Answer 1

It loses its water and swells up. on further heating it turns into a transparent liquid, which solidifies into glass like material. Borax=Na2B4O10=NaBO2+B2O3

Answer 2

NaBO2+B2O3

Answer 3

white crystalline solid, with soapy touch. It has a layer structure in which planar BO3 units are joined by hydrogen bonds. a weak monobasic acid; a Lewis acid

Answer 4

Acidifying aqueous borax Borax +HCl+H2O=NaCl+H3BO3

Answer 5

First metaboric acid HBO2 is formed and on further heating B2O3 is formed

Answer 6

Diborane is a colourless, highly toxic gas. Diborane catches fire spontaneously upon exposure to air

Answer 7

It is prepared by treating BF3 with LiAlH4 BF3 + LiAlH4 = B2H6 + LiF + AlF3

Answer 8

oxidation of sodium borohydride with iodine. NaBH4 + I2 = B2H6 + NaI + H2

Answer 9

Diborane is produced on an industrial scale by the reaction of BF3 with sodium hydride. BF3 +NaH=B2H6+NaF

Answer 10

Symmetrical cleavage B2H6+NMe3=BH3.NMe3 B2H6 +CO=BH3.CO

Answer 11

Unsymmetrical cleavage B2H6 +NH3=[BH2(NH3)2]+[BH4]- This on heating gives B3N3H6

Answer 12

-Bullet proof vests -aircraft -protective shields in nuclear industry as it can absorb neutrons -heat resistant glass, glass wool, fibreglass -flux -medicinal soaps

Answer 13

-aqueous solution is used as antiseptic

Answer 14

-alloys -packing, utensil making, aircrafts

Answer 15

C>Si>Ge>Pb>Sn

Answer 16

C>Pb>Si=Ge=Sn

Answer 17

C>Si>Ge>Pb>Sn

Answer 18

C>Si>Ge=Sn

Answer 19

Si>Ge>Sn>Pb

Answer 20

C-+4; Si-+4; Ge-+4; Sn-+4 (+2 acts as a reducing agent); Pb-+2 (+4 acts a an oxidising agent)

Answer 21

All members form oxides when heated in O2.

Answer 22

Acidic: CO2, SiO2;GeO2,GeO Neutral: CO Amphoteric: SnO, SnO2, PbO, PbO2 *SiO only exists at high temperature

Answer 23

C, Si, Ge- No reaction Sn: decomposes steam to form oxide Sn + 2H2O = SnO2 + H2 Pb-No reaction due to the formation of protective layer

Answer 24

Gives Si(OH)4 i.e. Silicic acid

Answer 25

tetrachlorides are easily hydrolysed by water because the central atom can accommodate the lone pair of electrons from oxygen atom of water molecule in d orbital.

Answer 26

PbI4 does not exist because Pb—I bond initially formed during the reaction does not release enough energy to unpair 6s2 electrons and excite one of them to higher orbital to have four unpaired electrons around lead atom.

Answer 27

React directly with halogens (except C) to form MX2 and MX4. Mostly covalent (except PbF4, SnF4 are ionic)

Answer 28

PbF4, SnF4

Answer 29

because C doesnt have d-orbitals to accommodate the lone pair from H20

Answer 30

Heavier elements do not form p(pi)– p(pi) bonds because their atomic orbitals are too large and diffuse to have effective overlapping.

Answer 31

In diamond each carbon atom undergoes sp3 hybridisation and linked to four other carbon atoms by using hybridised orbitals in tetrahedral fashion. The structure extends in space and produces a rigid three dimensional network of carbon atoms. It is very difficult to break extended covalent bonding and, therefore, diamond is a hardest substance on the earth

Answer 32

-abrasive for sharpening hard tools -in making dyes -in the manufacture of tungsten filaments for electric light bulbs.

Answer 33

Graphite has layered structure. Layers are held by van der Waals forces. Each layer is composed of planar hexagonal rings of carbon atoms. Graphite cleaves easily between the layers and, therefore, it is very soft and slippery.

Answer 34

graphite is used as a dry lubricant in machines running at high temperature

Answer 35

Fullerenes are made by the heating of graphite in an electric arc in the presence of inert gases such as helium or argon.

Answer 36

Fullerenes are the only pure form of carbon because they have smooth structure without having ‘dangling’ bonds.

Answer 37

5-membered --12 6--membered--n/2-10

Answer 38

Graphite since it is more stable thermodynamically.

Answer 39

Obtained from burning hydrocarbons in a limited supply of air.

Answer 40

heating wood at high temperatures in the absence of air.

Answer 41

heating coal at high temperatures in the absence of air.

Answer 42

-Graphite is used as electrodes in batteries - activated charcoal is used to absorb poisonous gases and in water filters and in airconditioning systems -Carbon black is used as a black pigment and filler in tyres - Coke is used as fuel and as a reducing agent in metallurgy

Answer 43

Carbon monoxide is a colourless, odourless and almost water insoluble gas. It is a powerful reducing agent and reduces almost all metal oxides. Because of the presence of a lone pair on carbon, CO molecule acts as a donor and reacts with certain metals when heated to form metal carbonyls.

Answer 44

C+O2(limited)=CO HCOOH+H2SO4=CO+H2O

Answer 45

It is a colourless and odourless gas. Its low solubility in water makes it of immense biochemical and geo-chemical importance. H2CO3/HCO3 – buffer system helps to maintain pH of blood between 7.26 to 7.42.

Answer 46

C+O2=CO2 CH4+O2=CO2+H2O CaCO3+HCl=CaCl2+CO2 commercially it is prepared by heating limestone

Answer 47

-used as a fire extinguisher -used in manufacture of NH3

Answer 48

Quartz, cristobalite, tridymite

Answer 49

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 forming 8-membered rings.

Answer 50

HF, NaOH SiO2 +NaOH =Na2SiO3 + H2O SiO2 + HF = SiF4 + H2O

Answer 51

Amorphous silica (used in filtration plants

Answer 52

-quartz is used as a piezoelecctric material, used in clocks, radio, television, mobile communication -silica gel is used as a drying agent

Answer 53

They are a group of organosilicon polymers, which have (R2SiO) as a repeating unit.methyl chloride reacts with silicon in the presence of copper as a catalyst at a temperature 573K various types of methyl substituted chlorosilane of formula MeSiCl3, Me2SiCl2, Me3SiCl with small amount of Me4Si are formed, which on hydrolysis form straight chain polymers

Answer 54

The chain length of the polymer can be controlled by adding (CH3)3SiCl which blocks the ends

Answer 55

A large number of silicates minerals exist in nature. Some of the examples are feldspar, zeolites, mica and asbestos. The basic structural unit of silicates is (SiO4)4–. Two important man-made silicates are glass and cement.

Answer 56

If aluminium atoms replace few silicon atoms in three-dimensional network of silicon dioxide, overall structure known as aluminosilicate. Examples are feldspar and zeolites. Zeolites are widely used as a catalyst in petrochemical industries for cracking of hydrocarbons and isomerisation.

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