Preparation and Properties of Compounds

8/11/2019 Preparation and Properties of Compounds

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Page No.-1

Preparation & Properties of Compounds

ORON FAMILY

Elements : B, Al, Ga, In, Tl

General eletroni onfiguration : 2 1ns , np

!elting Points, Boiling Points and strutures

The melting points of group III elements do not show a regular trend as did the metals of group Iand II, because B and Ga have unusual crystal structures.Boron has an unusual crystal structure which results in the melting point being very high. Otherelements form metallic bonding, but small sie and high lonisation energy ma!e this impossiblefor boron. Boron e"ists in four different allotropic forms, all of which contains icosahedral unitswith boron atoms at all 12 corners. #Icosahedral contains 12 corners and 2$ faces%. Only &'( ofthe space is occupied by the atoms, compared with ')( for a close*pac!ed arrangement. Thisshows that icosahedra fill up space ineffectively.The elements +l, In and TI all have close*pac!ed metal structures Ga has an unusual structure.

ach metal atom has one close neighbour at a distance of 2.)& - and si" more distant neighboursat distance between 2.' - and 2.' -. This remar!able structure tends towards discrete diatomicmolecules rather than a metallic structure. This accounts for the incredibly low melting point ofgallium at &$/0

!elting Point "#C$ Boiling Point "#C$

B+lGaInTl

21$$&$13'&$&

&3$2)'2)$&2$$1)3'

+s is obvious from the above table, the melting point decreases in the group but irregularitiesoccur. B has very high melting point because of its uni4ue covalent structure. Ga has e"tremelylow melting point again because of its uni4ue structure.The boiling point for B is unusually high, but the values for Ga, In and Tl decrease ondescending the group as e"pected. 5ote that the boiling point for Ga is in line with the others,whereas its melting point is not. The very low melting point is due to the unusual crystalstructure, but the structure no longer e"its in the li4uid.

%ie of atoms and ions

The metallic radii of the atoms do not increase regularly on descending the group. 6owever, thevalues are not strictly comparable because of their uni4ue structures.

7etallic radius#-%

Ionic radius

( )&7 -+ ( )7 -+8aulingselectronegativity

B+lGaInTl

#$.3%1.)&

#1.223%1.'1.'$

#$.2'%$.3&3$.2$$.$$$.3

991.21.)1.3

21.31.1.'1.

The ionic radii for &7+ increase down the group, though not in the regular way as observed inGroup I and II. There are two reasons for this.

NA'A(ANA )*A'+A CENT'E1-A, )imension )urga Toer, Plot No. / 1, %etor 0 !aret, )ara Ne )el2i / 1134, P2 : 045130 6 4


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Page No.-

Preparation & Properties of Compounds#i% There is no evidence for the e"istence of &B+ under normal condition and the value of

ionic radius is an estimate.#ii% The electronic structures of the elements are different Ga and In have a 1$d inner shell

which is poorly screening and so have higher ionisation energies than would otherwise bee"pected. This contraction in sie is sometimes called the d*bloc! contraction.

In a similar way Tl follows immediately after 1) f*bloc! elements.. The sie andionisation energy of TI are affected even more by the presence of 1) f*electrons, whichshield the nuclear charge even less effectively. The contraction in sie from these f*bloc!elements is called the lanthanide contraction.

Eletropositi7e C2arater

The electropositive or metallic nature of the elements increase from B to +l, but thendecreases from +l to TI as is shown by the standard electrode potentials for the reaction:

&7 &e 7+ +

( )&7 ; 7


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Page No.-9

Preparation & Properties of CompoundsPreparation:

"i$ Boron is obtained by the reduction of B2O&with magnesium or sodium B2O& is firstprepared by strongly heating 6&BO&which is obtained by the action of 60l or 62AO)on aconcentrated solution of bora":

5a2B)O'> 260l > 362O )6&BO&> 25a0l26&BO& B2O&> &62O

B2O&> &7g 2B > &7gO

8ure crystalline boron may be obtained in small 4uantities by the reduction of BBr&with62on a heated metal filament at 12'3*1)'3 .

"ii$ !odern !et2od

B is obtained these days by the electrolysis of a fused mi"ture containing boric anhydride, 7gO

and 27g? at 11$$/0. The electrolysis is done in a carbon crucible, which acts as anode and ?e

rod is used as cathode. The 7g discharged at cathode reduces 2 &B O to B.

2

2 &

27gO 27g O

B O &7g 2B &7gO

+

+ +B thus obtained is heated electrically in vacuum at 11$$/0, when the impurities are volatilisedoff and pure boron is obtained.

"iii$ By thermal decomposition of &BI over red hot tungsten filament #


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Page No.-0


2 2 22B 25aO6 26 O 25aBO &6+ + +

2 2 & 22B &6 O B O &6+ +

o"idation

2 ) & & 22B &6 AO 26 BO &AO+ +

o"idation& & & 22B 65O 6 BO 5O+ +

). Boron reacts with 7g and conse4uent hydrolysis gives diborane.

& 2&7g 2B 7g B+

& 2&0a 2B 0a B+

& 2 2 2 7g B 60l &7g0l B 6+ +

2 2 & & 2B 6 6 O 26 BO 6+ +

3. Boron reduces silica and 0O2

2 2 &&AiO )B 2B O &Ai+ +

2 2 &&0O )B 2B O &0+ +

Illustration - 1

Chich of the statement is true for the above se4uence of reactions #a% H is hydrogen #b% is B

26

#c% H and J are ?2and B

26

respectively #d% H is potassium hydro"ide

Ans. "$

Note : + 2 3(Z ) ( X)

B F BF ;

3 2 6 4(Y )

8BF 6LiH B H 6 LiBF+ +

COMPOUNDS OF BORAN

Diborane (B2H6)

Preparation: Kiborane can be prepared in almost 4uantitative yields by the reduction of borontrifluoride etherate #B?&.Ot2% with lithium aluminium hydride #Di+l6)% orsodium borohydride #5aB6)%.

2,t O

& 2 ) 2 ) 2)B? .Ot &Di+l6 2B 6 &Di+l? )t O+ + +

diglyme

& 2 ) 2 ) 2)B? .Ot &5aB6 2B 6 &5aB? )t O+ + +



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Page No.-4

Preparation & Properties of Compoundswhere, diglyme is diethyleneglycol dimethyl ether, #7eO062062%2O.

Kiborane can also be prepared by treating 5aB6)with conc. 62AO)or 6&8O):

) 2 ) 2 2 2 )25aB6 6 AO B 6 26 5a AO+ + +

) & ) 2 2 2 )25aB6 26 8O B 6 26 25a6 8O+ + +

Properties: 1. Kiborane is a colourless gas #b.p., 1&%. It is rapidly decomposed by waterwith the formation of 6&BO&and 62:

2 2 & & 2B 6 6 O 26 BO 6+ +

2. 7i"tures of diborane with air or o"ygen inflame spontaneously produce largeamount of heat. Kiborane has a higher heat of combustion per unit weight offuel than most other fuels. Therefore, it is used as a roc!et fuel.

91

2 2 2 & 2B 6 &O B O &6 O, 6 9213 !L mol+ + =

&. 8yrolysis of B26 in sealed vessels at temperatures above &'3 is ane"ceedingly comple" process producing a mi"ture of various boranes, e.g.,B)61$, B36, B3611, B61$, B612 and B1$61). By careful control oftemperature, pressure and reaction time, the yield of various intermediate

boranes can be optimised. ?or e"ample, by storing B26under pressure for 1$days, B)61$is produced in 13( yield according to the following e4uation:

2 ) 1$ 22B 6 B 6 6 +

). Kiborane reacts with ammonia gives inorganic benene

2 & & & 2& 2 12

# %

+ +B H NH B N H H

inorganicbenzene

Illustration -

Chen an inorganic compound #% having &0 9 2e as well as 2e 9 2e bonds reacts with ammoniagas at a certain temperature, gives a compound #J%, isostructural with benene. 0ompound #%with ammonia at a high temperature produces a substance #H%.

#a% #% is B26 #b% #H% is !nown as inorganic graphite

#c% #J% is B&5

&6

#d% #H% is soft li!e graphite

+ns. #a, b, c%Note: Kiborane, B

26

, is a compound consisting &092e and 2e 9 2e bonds. B

26

> 256

& Low temp.

B26

200C3 3 4

( Y)

B N H M 256& . #J% has structure similar to benene. It is called inorganic

benene. + High temp.

2 6 3 X(Z )

B H NH (BN) . #H% is a hard substanceN.

3. Kiborane undergoes a facile addition reaction with al!enes and al!ynes in

ether solvents at room temperature to form organoboranes:

06 P 062> B26 2B#062062%ydroboration eaction%



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Page No.-5

Preparation & Properties of CompoundsIllustration - 9

Chich one of the following compounds does not e"ists

#a% B26

)#06

&%

2#b% B

26

&%

c% B

26

2#06

&%

)#d% B

26#06

&%

3

+ns. #d%Note 5ot more than four hydrogen atoms can be substituted by methyl groups in the molecule of B

26

.

The bridge hydrogen atoms are not to be substituted.

Boric Acid: Orthoboric acid 6&BO&commonly !nown as boric acid and metaboric acid 6BO2,are two well*!nown and important o"oacids of boron.

Preparation: On a large scale, 6&BO& is prepared by the action of 60l or 6 2AO) on aconcentrated solution of bora":

2 ) ' 2 & &5a B O 260l 36 O )6 BO 25a0l+ + +

Properties: 1. Boric acid is a fla!y, white crystalline solid.

2. It is moderately soluble in water.

&. Boric acid is a very wea! monobasic acid #p P .23%, because it acts as anelectron pair acceptor #Dewis acid% from 9O6 rather than as a proton donor#+rrhenius acid%.

9

& & 2 ) &6 BO 26 O QB#O6% N 6 O++ +

). On heating boric acid at &'3 , metaboric acid, 6BO2is formed. On further

heating above 3$$ , B2O&is formed:&'3 B

& & 2 26 BO 6BO 6 O + F 3$$ B2 2 & 226BO B O 6 O +

In solution metaboric acid changes into orthoboric acid.

Borax(Sodium tetraborate decahydrate, Na2B4O7. 10H2O)

Preparation: It is obtained by e"tracting impure bora" with water and then concentrating thesolution until crystals of bora" separate out.

Bora" can also be prepared from the mineral colemanite by boiling it with 5a20O&solution::

2 11 2 & 2 ) ' 2 &0a B O 25a 0O 5a B O 25aBO 20a0O+ + +

Properties: 1. Bora" is a white crystalline solid. It is hydrolysed by water to give an al!alinesolution:

2 ) ' 2 & &5a B O '6 O )6 BO 25aO6+ +

2. On heating, bora" loses water to become anhydrous. +nhydrous bora" onstrong heating with 56)0l gives boron nitride and boron trio"ide:

2 ) ' ) 2 & 25a B O 256 0l 2B5 B O 25a0l )6 O+ + + +

&. On heating alone, it decomposes to form 5aBO2and B2O&

2 ) ' 2 2 &5a B O 25aBO B O +



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Page No.-3

Preparation & Properties of CompoundsIllustration -0

5a2B

)O

'M 1$6

2O is correctly represented as

#a% 25aBO2M 5a

2B

2O

&M 1$6

2O #b% 5a

2QB

)O

3#O6%

)N M 6

2O

#c% 5a2QB)O3#O6%)N M 62O #d% 5a2QB)#62O%)O'N M 62O

+ns. #b%Note Bora" molecule is actually made of two tetrahedra and two triangular units Roined as shown

below :

N a 2 H O ! B

O ! B ! O

O ! B

O

! O

B ! O H

O H

O H

Illustration - 4

+morphous boron is e"tracted from bora" by following steps :

Bora" ( ") Heat (B)3 3 2 3H BO B O Bo#o$

#a% 62AO

), +l #b% 60l, carbon #c% 6

2AO

), 7g #d% 60l, ?e

+ns. #c%

Note 5a2B

)O

'> 6

2AO

)> 36

2O 5a

2AO

)> )6

2BO

&F +2 3 2 3 22H BO B O 3H O;

+ +2 3B O 3%g 2B 3%gO&

). Bora ;ead Test:The formation of coloured metaborates by transition metalsalts is used in bora" bead test in 4ualitative analysis. The colour depends onthe o"idising or reducing flame of the bunsen burner.

+ cupric salt forms blue cupric metaborate in the o"idising flame:

5a2B)O'> 0uO 0u#BO2%2> 25aBO2

In the reducing flame , #ie. in presence of carbon % the coloured salt is reducedto colourless cuprous metaborate:

20u#BO2%2> 25aBO2> 0 20uBO2> 5a2B)O'> 0O. and to metalliccopper and hence bead becomes dull red and opa4ue.20u#BO2% > )5aBO2> 20 20u > 25a2B)O'> 20O

Compounds ofColour of ;ora ;ead


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Page No.-=


Aluminium

Aluminium oxide - Al2O3(Alumina)

Preparation: In the lab, it is prepared by igniting aluminium hydro"ide, aluminium sulphate or

ammonium alum.2+l#O6%& +l2O&> &62O+l2#AO)%& +l2O&> &AO8)%2AO).+l2#AO)%&.2)62O 256&> +l2O&> )AO&> 2362O

Properties: Chite crystalline powder and it is an amphoteric o"ide.+l2O&> 60l 2+l0l&> &62O+l2O&> 25aO6 25a+lO2> 62O

Aluminium Chloride: AlCl3.6H2O

Preparation: It is prepared by the action of dil or conc. hydrochloric acid on aluminium

2+l > 60l 2+l0l&> &62

i% +luminium chloride e"ists as dimer #+l20l% in inert solvent as well as invapour state.

ii% It is a white crystalline, hygroscopic solid and it fumes in moist air due tohydrolysis.

+l0l&> &62O +l #O6%&> &60l

Alums:

+lums are the double sulphates having general formula: 2AO).72#AO)%&.2)62O

P monovalent cation such as 5a>, >, 56)>etc.7 P trivalent cation such as +l&>, 0r&>, ?e&>etc.

when alum contains aluminium as trivalent cation then it is named after monovalent cation.

e.g. 2AO).+l2#AO)%&.2)62O potash alum5a2AO).+l2#AO)%&.2)62O * Aoda alum.

Chen trivalent cation is not aluminium then alum is named after both, monovalent as well as

trivalent cation.

#56)%2AO).?e2#AO)%&.2)62O * ferric ammonium alum.

Illustration - 5

Chich of the following minerals does not contain aluminium

#a% 0ryolite #b% 7ica #c% ?eldspar #d% ?luorspar

+ns. #d%

Note : 0ryolite 9 5a&

+l?

F ?eldspar 9 +lAi&

O

S

Q7ica 9 2O M &+l

2O

&MAiO

2M 26

2OF ?luorspar 9 0a?

2N



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Page No.->


Illustration - 3

The function of luorspar in the electrolytic reduction of alumina dissolved in fused cryolite#5a

&+l?

% is

#a% as a catalyst

#b% to lower the temperature of melt and to ma!e the fused mi"ture very conducting

#c% to decrease the rate of o"idation of carbon anode

#d% none of these

Ans. ";$

Illustration - =

+l2O&can be converted to anhydrous +l0l&by heating

#a% a mi"ture of +l2O

&and carbon in dry 0l

2 gas

#b% +l2O

&with 0l

2gas

#c% +l2O

&with 60l gas

#d% +l2O

&with 5a0l in solid state

Ans. "a$

?int:+l2O&> &0 > &0l22+l0l&> &0ON

Illustration - >

6ydrated +l0l&is used as

#a% catalyst in crac!ing of petroleum #b% catalyst in ?riedel*0raftSs reaction

#c% mordant #d% all of these

Ans "$

Illustration - 1

+l0l&on hydrolysis gives

#a% +l2O

&M 6

2O #b% +l#O6%

c% +l

2O

d% +l0l

&M 6

2O

Ans ";$



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Page No.-1


CA'B


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Page No.-11

Preparation & Properties of Compounds;$Amorphous form:0oal, 0o!e, 0harcoal #or wood charcoal%, animal charcoal #or bone blac!%,

Damp blac!, 0arbon blac!, Gas carbon and 8etroleum co!e are the amorphous form of carbon.

Structure of Diamond: In diamond, the carbon atoms are arranged tetrahedrally#sp&hybridisation of 0%: ach 0 atom is lin!ed to its neighbours by four single covalent bonds. This

leads to a three*dimensional networ! of covalent bonds. It is because of this, that diamond is very hardand has high melting and boiling points. Aince, all the valence electrons of carbon are used up in formingthe covalent bonds, hence diamond does not conduct electricity.

Structure of Graphite:In graphite, the carbon atoms are arranged in regular he"agons in flatparallel layers. ach carbon in these layers is bonded to three other by sp2covalent bonds. This givessome double bond character to graphite. ach layer is bonded to the adRacent layers by wea! vanderCaalSs forces. +s a result, each layer can slide over the other easily. It is because of this structure thatgraphite is soft and slippery and can act as a lubricant. The presence of double bond character #the

presence of delocalised *electrons% ma!es graphite a good conductor of electricity.

Oxides:0arbon burnt in air forms two o"ides, carbon mono"ide, 0O and 0arbon dio"ide 0O2.

a)Carbon Monoxide (CO)

Preparation: i% By heating carbon in limited supply of o"ygen.

0 >2

'O2 0O.

ii% By heating o"ides of heavy metals e.g. iron, inc etc with carbon.?e2O&> &0 2?e > &0OHnO > 0 Hn > 0OTwo important industrial fuels water gas and producer gas contain carbonalong with hydrogen and nitrogen, Cater gas is obtained by passing steamover hot co!e

0 > 62O 2#water gas%0O 6+

Chen air is passed over hot co!e, producer gas is obtained.

20 > O2> )52 2#producer gas%20O )5+

Properties: i% It is powerful reducing agent and reduces many metal o"ides to thecorresponding metals e.g.

?e2O&> &0O 2?e > &0O20uO > 0O 0u > 0O2

ii% It burns in air to give heat and carbon dio"ide

0O >1

2O2 0O2> heat.

Tests: a% Burns with blue flame

b% + filter paper soa!ed in platinum or palladium chloride is turned pin!,green or blac! due to reduction of the chloride by carbon mono"ide.

b)Carbon di-oxide (CO2):

Preparation: i% In the lab., it is prepared by the action of acids on carbonates.



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Page No.-1

Preparation & Properties of Compounds0a0O&> 260l 0a0l2> 62O > 0O2

ii% By combustion of carbon0 > O2 0O2

Properties: i% It turns lime water mil!y and mil!iness disappears when 0O2is passed in

e"cess0a#O6%2> 0O2 0a0O&> 62O0a0O&> 62O > 0O2 0a#60O&%2

ii% Aolid carbon dio"ide or dry ice is obtained by cooling 0O2under pressure.It passes to the solid state straight from gaseous state without li4uefying#hence dry ice%.

iii% + burning candle is put out but burning magnesium continues burning inthe gas Rar.

Carbides:0arbon combines with more electropositive elements than itself when heated to high

temperature to form carbides. 0arbides are of mainly three types.

i% Salt like Carbides:These are the ionic salts containing either 022*#acetylide ion% or 0)*

#methanide ion%e.g. 0a02, +l)0&, Be20.

ii% Covalent Carbides:These are the carbides of non*metals such as silicon and boron. Insuch carbides, the atoms of two elements are bonded to each other through covalent bonds.Ai0 is also !nown as 0arborundum.

iii%Interstitial Carbides:

They are formed by transition elements and consist of metalliclattices with carbon atoms in the interstices. e.g. tungsten carbide C0, vanadium carbide 6

2AO

)> 6

2O 2

2AO

)> ?eAO

)> 8

)%

2AO

)> 0ON



13/74

Page No.-19


Illustration - 19

The number and type of bonds between two carbon atoms in 0a02are#a% one sigma and one pi bond

#b% one sigma and two pi bonds

#c% one sigma and one and a half pi bonds

#d% one sigma bond

Ans ";$

?int :

Illustration - 10

C a C O ( )3

H e a t( " ) ( ) ( B ) ( g )

C a # * o $h e a t

( C ) ( ) ( + ) ( g )

( C ) ( ) H O ( , ) ( g )2

The 0ompound #% #g% is

#a% 0O #b% 0O2

#c% 06)

#d% 026

2

Ans. "d$

?int : +Heat

3(" ) (B)

CaCO CaO CO

+ +Heat 2(+)(C )

CaO C CaC CO

+ +2 2 2 2 2(,)

CaC 2H O Ca(OH) C H &

Silicon

Etration: 0ommercial form of silicon is obtained by reduction of AiO2with 0 or 0a02in an electricfurnace. 6igh purity silicon is obtained either from Ai0l)or from Ai60l&. These volatilecompounds are purified by e"haustive fractional distillation and then reduced with very

pure Hn or 7g. The resulting spongy Ai is melted, grown into cylindrical single crystaland then purified by one refining.

Properties: Ailicon is obtained by the reduction of silica. It e"ists in two allotropic forms: #a%amorphous and #b% crystalline. The amorphous variety is obtained by heating dry

powdered silica with magnesium.



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Page No.-10


2AiO 27g Ai 27gO+ +

1. The crystalline variety is obtained by heating a finely powdered sand or 4uart withcarbon and in electric furnace a small amount of iron is added to prevent theformation of carborundum #Ai0%.

2AiO 20 Ai 20O+ +2. +morphous silicon is chemically more reactive than crystalline silicon. +morphous

silicon is brownish powder. It burns brilliantly in o"ygen and ignites spontaneously influorine.

2 2Ai O AiO+

2 )Ai 2? Ai?+

&. It decomposes steam at red heat. It dissolves in the mi"ture of 65O& and 60l.6owever, it dissolves readily in al!aline medium.

2 2Ai 26 O AiO+ >2622 )Ai 2? Ai?+

). It combines with certain metals forming silicides

227g Ai 7g Ai+

3. Chen amorphous silicon is strongly heated, it fuses and on cooling solidifies to thecrystalline form. It is very hard crystalline silicon, does not burn in o"ygen but itreadily combines with fluorine. It dissolves in mi"ture of 65O&and 6?. Chen fusedwith al!ali, it gives a silicate.

2 & 2 &5a 0O Ai 5a AiO 0+ +

Silicones:Ailicones are a group of organo silicon polymers. Unli!e Ai0l )which on completehydrolysis gives AiO2, al!yl substituted chlorosilanes on hydrolysis do not give the e"pectedsilicon compound analogous to !etone but get hydrolysed to long chain polymers or silicones.Chile the hydrolysis of trial!ylmonochlorosilane yields he"al!yldisilo"ane, theal!yldichlorosilane gives straight chain polymers with active hydro"yl groups at each end of thechain and trichlorosilane gives comple" cross*lin!ed polymers. The chain sie is limited by thesie of al!yl group and the amount of cross*lin!ing is regulated by the relative amounts of di*and tri*methylchlorosilanes

Ai

O

O

Ai

Ai

O

0yclic silicone

Ai

O

O

O

Ai

O

06&

06&

O

O

O

O

06&

O

06&

0ross lin!ed silicone polymer

Ai

O Ai

O Ai

O

Dinear silicone polymer

Silicates:Ailicates are regarded as the salts of silicic acid, 6 )AiO). +ll the silicates are

comprised of AiO)units. These units have a tetrahedral structure formed as a result of sp &

hybridistion.



15/74

Page No.-14


Ailicon atom has its complete octet but each o"ygen atom is still short ofone electron to complete its octet. They can complete their octet by ta!ingup ) electrons from a metal, getting converted to an anion QAiO)N)9.

O Ai

O

O

O

The QAiO)N)9tetrahedral can be represented in three ways

Ai

OO

O

O

O O

O

O

O

O

'epresentations of)9

)AiO tetra2edra

In some silicates, the o"ygen atoms of AiO) units tend to complete their octet by sharingelectrons with other silicon atoms, the o"ygen atoms, thus, form bridges of the type AiVOVAi toother silicon atoms. The number of such bridges can vary from one to four. This leads to the

formation of comple" silicates. +ny o"ygen which fails to pic! up electrons from the othersilicon atom is not able to complete its octet. The resulting silicate chains are, therefore,negatively charged anions. The metal cations generally present in silicate minerals are Di >, 5a>,>, 0a2>, +l&>, etc. Kepending upon the way these AiO)units are lin!ed, silicates of differentstructure and comple"ity are obtained. Aome representative types are:

#a% pyrosillicate #b% cyclic silicate #c% chain silicate

#d% sheet silicate

Silicon Carbide or (Carborundum)

Preparation: Ai0 is made commercially by reducing silicon with carbon in an electricresistance furnace.

AiO2> &0 Ai0 > 20O

Properties: It is e"tremely hard and is very difficultly fusible #does not decompose below22$$o0%



16/74

Page No.-15

Preparation & Properties of CompoundsIt resists most chemical reagents but is o"idised by fused 5aO6 in contact withair.

Ai0 > )5aO6 > 2O2 5a20O&> 5a2AiO&> 262O

In Ai0, carbon and silicon atoms are alternate and are each surroundedtetrahedrally. It is widely used as an abrasive for grinding, cutting and polishing.

Illustration - 14

Chich of the following is correct

#a% Ailicones are organosilico polymers containing Ai V O V Ai lin!age

#b% &Ai0l on hydrolysis gives

&Ai V O V Ai

&

#c% Both of these#d% Both #b% and #c%

Ans. "$

Illustration - 15

In silicon dio"ide

#a% each silicon atom is surrounded by four o"ygen atoms and each o"ygen atom is bonded to two

silicon atoms#b% each silicon atom is surrounded by two o"ygen atoms and each o"ygen atom is bonded to two

silicon atoms

#c% silicon atom is bonded to two o"ygen atoms

#d% there are double bonds between silicon and o"ygen atoms

Ans. "a$

?int :Q ach silicon atom is surrounded tetrahedrally by four o"ygen atoms

- -

- -

- -O O

!O!i ! O !i ! O !&

O O

- -

Illustration - 13

The compound #0% is

#a% AiO2 #b% Ai #c% Ai0 #d% 5a2AiO&

Ans. "d$



17/74

Page No.-13


?int:Q + 2 3Na COHeat

4 2 4 2 2 3Heat(") (C )

iC/ H O i(OH) iO Na iO &

Illustration - 1=

Chen a mi"ture of air and steam is passed over red hot co!e, the outgoing gas contains

#a% producer gas #b% water gas

#c% coal gas #d% mi"ture of #a% and #b%

+ns. #d%

?int: + + + +2 2 2# o1e# ga team ate# ga

Co5e ai# CO N ; Co5e H O CO H &


18/74

Page No.-1=

Preparation & Properties of CompoundsProperties

It is a white powder, insoluble in water. It is somewhat unreactive. 6owaver, it dissolves in

concentrated 2 )6 AO forming stannic sulphate.

2 2 ) ) 2 2AnO 26 AO An#AO % 26 O+ +

Chen the solution is diluted, stannic o"ide is reprecipitated.

( )) 2 2 2 )2An AO 26 O AnO 26 AO+ +It readily dissolves in al!alies forming stagnates.

2 2 & 2AnO 2O6 AnO 6 O+ +

%tannous 2loride " ( )2An0l

Preparation

#i% 6ydrated stannous chloride 2 2An0l .26 O is prepared by dissolving tin in hot concentrated

hydrochloric acid and subRecting the solution to crystalliation.

2 2An 260l An0l 6+ +

6ydrated stannous chloride consists of two molecules of water as water of crystalliation

2 2#An0l .26 O%.

+nhydrous salt cannot be obtained by heating the hydrated salt as it undergoes hydrolysisand a white solid of tin hydro"yl chloride is formed.

2 2 2An0l .26 O An#O6%0l 60l 6 O + +

It can also be obtained when a mi"ture of An and calculated 4uantity of mercuric chlorideis heated.

2 2An 6g0l An0l 6g+ +

Properties

#i% It is a white crystalline solid. It is soluble in water, alcohol and ether.#ii% In water, it is soon hydrolysed. 6owever in presence of 60l #acid%, hydrolysis is revered.#iii% It forms a white precipitate with al!alies. The precipitate of stannous hydro"ide, however,

dissolves in e"cess of al!ali.

2 2An0l 25aO6 An#O6% 25a0l+ +

2 2 2 2An#O6% 25aO6 5a AnO 26 O+ +

#iv% It forms a dar! brown precipitate of stannous sulphide on passing 26 A through its

solution. The precipitate dissolves in yellow ammonium sulphide.

2 2An0l 6 A AnA 260l+ +

) 2 2 ) 2 &

Jellowammonium +mmoniumthiostannate

Aulphide

AnA #56 % A #56 % AnA+

#v% It is a strong reducing agent. ?ew e"amples are given below:#a% It reduces mercuric chloride to mercurous chloride #white ppt% and finally to metallic

mercury #dar! grey or blac!%2 2 2 2 )

7ercurouschloride

26g0l An0l 6g 0l An0l+ +

2 2 2 )6g 0l An0l 26g An0l+ +

#b% It reduces ferric salts to ferrous salts and cupric salts into cuprous salts.

& 2 2 )2?e0l An0l 2?e0l An0l+ +

2 2 )20u0l An0l 20u0l An0l+ +#c% It decolourises iodine and thus can be titrated with it.



19/74

Page No.-1>


2 2 )An0l 260l I An0l 26I+ + +

#d% Organic nitro compounds are reduced to amino compounds.

3 2 2 3 2 ) 2

5itrobenene +niline

0 6 5O 60l &An0l 0 6 56 &An0l 26 O+ + + +

#e% Its reduces gold chloride to metallic gold.& 2 )

0olloidalgold

2+u0l &An0l 2+u &An0l+ +

An0l)undergoes hydrolysis forming stannic acid which absorbs colloidal particle of goldand thus forms purple of cassius.

%tanni 2loride )#An0l %

Preparation

2 )An 20l An0l+ Properties

#i% It is a colourless fuming li4uid having disagreeable smell.#ii% It is hygroscopic and forms crystalline hydrates containing &, 3, and molecules

of water as water of crystalllisation. The pentahydrate ) 2An0l .36 O, is !nown as

Wbutter of tinX or Wo"ymuriate of tinX.#iii% It is soluble in water in which it undergoes hydrolysis.

An0l) )62O An #O6%)> )60lIt is also soluble in organic solvents showing that it is a covalent compound.

#iv% It dissolves in concentrated 60l forming chlorostannic acid. In presence ofammonium chloride, it forms ammonium salt of this acid.An0l)> 260l 62An0l

0hlorostannic acid

An0l)> 256)0l #56)%2An0l+mmounium chlorostannate


20/74

Page No.-

Preparation & Properties of CompoundsOn heating in air at )'$/0, it forms red lead.

2 & )8bO O 28b O+ #red lead%

'E) EA) ( )& )8b OPreparation

It is obtained by heating litharge at )'$/0 in air.o

)'$ 02 & )8bO O 28b O+

8ropertiesIt is a red powder, insoluble in water. Chen heated, it becomes almost blac!, but it again

becomes red on cooling. On heating above )'$/0, it decomposes into 8bO and 2O .

& ) 228b O 8bO O +

Chen treated with concentrated &65O

, lead nitrate and brownish blac! insoluble o"ide, 28bO

,are formed. This indicates that & )8b O is a compound o"ide containing both 28bO and 8bO in

the ratio of 1 : 2

( )& ) & & 2 228b O )65O 28b 5O 8bO 26 O+ + +

Cith 2 )6 AO , it evolves o"ygen,

& ) 2 ) ) 2 228b O 6 AO 8bAO 6 O O+ + +It acts as an o"idising agent.

& ) 2 2 2

& )

& ) 2

8b O 60l &8b0l )6 O 0l

8b O )0 &8b )0O8b O )0O &8b )0O

+ + +

+ ++ +

EA) C?


21/74

Page No.-1


NIT'


22/74

Page No.-

Preparation & Properties of CompoundsC2emial Properties :

O"idation Atates and trends in a chemical reactivity:The common o"idation states of these elements are 9&, >& and >3. The tendency to e"hibit 9& o"idationstate decreases down the group, bismuth hardly forms any compound in 9& o"idation state. The stability

of >3 o"idation state decreases down the group. The only well characteried Bi#3 o"idation state decreases and that of >& state increases #due to inert pair effect% downthe group.

& & & 3 3 3Bi Ab +s F Bi Ab +s+ + + + + +> > < 1 to >) tend to disproportionate in acid solution.

?or e"ample, 2 & 2&65O 65O 6 O 25O + +Aimilarly, in case of phosphorus nearly all intermediate o"idation states disproportionate into >3 and 9&

both in al!ali and acid. 6owever >& o"idation state in case of arsenic, antimony and bismuth becomeincreasingly stable with respect to disproportionation.

5itrogen is restricted to a ma"imum covalency of ) since only four #one s and three p% orbitals areavailable for bonding. The heavier elements have vacant d orbitals in the outermost shell which can be

used for bonding #covalency% and hence, e"pand their covalence as in 8? .

eactivity towards hydrogen :

+ll the elements of Group 13 form hydrides of the type &6 where P 5, 8, +s, Ab or Bi. Aome of the

properties of these hydrides are shown in Table. The hydrides show regular gradation in their properties.

The stability of hydrides decreases from &56 to &Bi6 which can be observed from their bond

dissociation enthalpy. 0onse4uently, the reducing character of the hydrides increases. +mmonia is only a

mild reducing agent while &Bi6 is the strongest reducing agent amongst all the hydrides. Basicity also

creases in the order & & & & &56 86 +s6 Ab6 Bi6> > >

P'


23/74

Page No.-9


e"ample, for the o"yacids of the type ( ) nmO6 HO , the acid strength varies directly with the

value of n. Thus, nitric acid ( )&65O is stronger than nitrous acid ( )265O .

The acids & 2 & & & )6 8O , 6 8O and 6 8O are appro"imately of e4ual strength, because all these

acids contain only one unhydrogenated o"ygen atom each. The order of acid strength is

& 2 & & & )6 8O 6 8O 6 8O> >

Nitrogen

Preparation: 1. ) 2 2 256 5O 5 26 O +

Aince ammonium nitrite is very unstable, it cannot be !ept as such. 6ence nitrogen isusually prepared by heating a mi"ture of ammonium chloride and sodium nitrite.

) 2 ) 256 0l 5a5O 56 5O 5a0l

+ +) 2 2 2

56 5O 5 26 O +

2. By heating ammonium dichromate: +mmonium dichromate on heating decomposesto give nitrogen gas.

) 2 2 ' 2 2 2 8 % 0r O 5 )6 O 0r O + +

& 2 2256 &0uO 5 #g% &0u &6 O+ + +

2 2 2 2 2 256 0O56 265O 25 0O &6 O+ + +

2 2

5a5O 60l 5a0l 65O+ +

2 2 2 2 2 256 0O56 265O &6 O 0O 25+ + +

@iation of atmosp2eri nitrogen in 8anamide fertilier "T2e 8anamide proess$

5itrogen is also fi"ed as calcium cyanamide on heating it with calcium carbide at 1$$$/0in an electric furnace.

electric furnace

2 2 2calcium carbide calcium cyanamide

0a0 5 0a05 0+ +

The mi"ture of calcium cyanamide and carbon #trade name nitrolim% is an importantfertilier.

0alcium cyanamide may also be used as a source of ammonia. The ammonia so producedcan be converted into useful fertiliers. 0alcium cyanamide is decomposed by water togive ammonia.

2 2 & &0a05 &6 O 0a0O 256+ +

& 2 ) ) 2 )256 6 AO #56 % AO+

& 2 ) ) 2 )256 6 AO #56 % AO+

2 3 & 2 ) & )8 O 56 &6 O 2#56 % 8O+ +

2 2 2 &0a0l 56 0a0l .56+



24/74

Page No.-0

Preparation & Properties of CompoundsIllustration - 1>

+mmonia will be obtained in

#a% 0a052> 6

2O #b% Heat4 2 4NH H O

#c% Both of these #d% 5one of these

Ans "$

?int:Q + +2 2 3 3CaCN 3H O CaCO 2NH ; + +4 2 4 3 3 2NH H O NH HO H O&

Illustration -

Chich one of the following compounds on strong heating evolves ammonia gas

#a% #56)%

20r

2O

'#b% 56

)5O

c% 56

)5O

2#d% #56

)%

2AO

)

Ans "d$

?int:Q 4 2 2 2 3 3 2(NH ) C# O N ; NH NO N O; 3 2 2 4 2 4 3NH NO N ; (NH ) O NH &

Oxides of Nitrogen

@ormula Name Colour 'emars

52O 5itrous o"ides 0olourless ather unreactive

5O 5itric o"ide 0olourless 7oderately reactive

52O& Kinitrogen trio"ide Kar! blue "tensively dissociated as gas

5O2 5itrogen dio"ide Brown 7oderately reactive

52O) Kinitrogen tetro"ide 0olourless"tensively dissociated to 5O2as gas andpartly as li4uid

52O3 Kinitrogen pento"ide 0olourless unstable as gasF ionic solid

5O&, 52O 5ot well characteried and 4uite unstable

Preparation: 1. 52O is obtained generally by heating 56)5O&:

) & 2 256 5O 5 O 26 O +52O is also !nown as laughing gas because it induces laughter mi"ed with 52.It is used as an anesthetic by dentists

2. 5O is best prepared by the reduction of 65O&with reducing agents li!e 0u orby reduction of nitrous acid or nitrites by ?e2> ofI9ions:

& & 2 2&0u 65O 20u#5O % 25O )6 O+ + +

2 ) 2 )

) 2 ) & 2

25a5O 2?eAO &6 AO

25a6AO ?e #AO % 25O 26 O

+ +

+ + +2 2 ) ) 2 2

25a5O 25aI )6 AO )5a6AO 25O I 26 O+ + + + +



25/74

Page No.-4

Preparation & Properties of Compounds5O is formed as an intermediate in the manufacture of nitric acid by o"idationof 56&.

&. 52O&is obtained as an intense blue li4uid or a pale blue solid on cooling ane4uimolar mi"ture of 5O and 5O2:

2 2 &5O 5O 5 O+

On warming, its colour fades due to its dissociation into these two o"ides.

). 5O2can be prepared by reduction of conc. 65O&with 0u or by heating heavymetal nitrates:

& & 2 2 20u )65O 0u#5O % 25O 26 O+ + +

& 2 2 228b#5O % 28bO )5O O + +

3. 52O3is an anhydride of 65O&. It is best prepared by dehydrating 65O&with8)O1$at low temperatures:

23$ B

& ) 1$ 2 3 &)65O 8 O 25 O )68O+ +

Properties: O"ides of nitrogen are all o"idiing agents. 52O even support the combustion of Aand 8. 5O which is thermally more stable, supports the combustion of 7g and 8

but not of A. Aulphur flame is not hot enough to decompose it 52O and 5O areneutral, while the other o"ides are acidic.

Di4uid 52O)undergoes self*ionisation to form 5O>and9

&5O ions and therefore,

it has been e"tensively studied as a non*a4ueous solvent. Aolid 52O3e"ists in the

ionic form, 92 &5O 5O+ . In the gaseous form, the discrete 52O3molecules have a 5

VOV5 bond angle close to 1$/.

Oxyacids: The most important o"o*acid of nitrogen is nitric acid 65O&

Preparation: i% In the lab, it is prepared by heating 5a5O&or 5O&with conc. sulphuric acidin a glass retort.

5a5O&> 62AO)5a6AO)> 65O&

ii% It is manufactured by the catalytic o"idation of ammonia and the process is!nown as Ostwald process

)56&> 3O2 8t OhE )5O > 62O25O > O2 112$ 25O2&5O2> 62O 265O&> 5O.

Properties: i% In a4ueous solution, nitric acid is a strong acid and dissociates to givehydronium and nitrate ions.

65O&> 62O 6&O>> 5O&*

ii% Ation on metals:0onc. nitric acid is a strong o"idising agent and attac!smost metals e"cept noble metals such as gold and platinum. The product ofreduction depend upon the concentration of the acid, temp and the nature of



26/74

Page No.-5

Preparation & Properties of Compoundsthe material undergoing o"idation. Cith dilute nitric acid the principle productis nitric o"ide 5O and with conc. nitric acid, the principle product is 5#I


27/74

Page No.-3


?int : + 2 2$C/ 7 HC/ HNO

3 2 2(X) (Y) (Z)

C 1i/. HNO NO NH OH 9 HC/ N O&

Illustration -

5itrogen forms 52but phosphorus is converted into 8

)from 8

2. The reason for this is

#a% triple bond is present between phosphorus atoms

#b% p*pbonding is wea!

#c% p*pbonding is strong

#d% multiple bond is formed easily

Ans. ";$

Illustration - 9

Chen +g5O&is heated strongly, the products formed are

#a% 5O and 5O2

#b% 5O2and 5

2O

#c% 5O2and O

2#d% 5O and O

2

+ns. #c%

Phosphorous

Etration: It is a very reactive element, so it does not occur free in nature. Kifferent ores are:

8hosphorite : 0aO)%2?luorapatite : &0aO)%20a?20hlorapatite: &0aO)%2. 0a0l2

8hosphorous is obtained by heating bone ash or phosphorite roc! 0a O)%2with sand#AiO2% and co!e #c% in an electric furnance at about 1''$ . The reactions are as thefollowing:

& ) 2 2 ) 1$ &20a #8O % AiO 8 O 0aAiO+ +

) 1$ )8 O 1$0 8 #v% 1$0O+ +Properties: i% 'eation it2 o8gen: Jellow phosphorus readily catches fire in air giving dense

white fumes of phosphorus pentao"ide. ed phosphorus combines with o"ygen onlyon heating. Both of them form either phosphorus trio"ide or phosphorus pentao"ide.

heat

) 2 2 &red phosphorous phosphorus trio"ide

8 &O 28 O+

heat

) 2 2 3red phosphorus phosphorus pento"ide

8 3O 28 O+

ii% 'eation it2 2lorine: 8hosphorus reacts with chlorine gas to form tri and

pentachlorides. Jellow phosphorus reacts violently at room temperature, whereas redphosphorus reacts on heating only.



28/74

Page No.-=


) 2 &phosphorus trichloride

8 0l )80l+

) 2 3phosphorus pentachloride

8 1$0l )80l+

iii% 'eation it2 alalies "sodium6potassium 28droide$: Jellow phosphorusdissolves in caustic soda on boiling under an inert atmosphere liberating phosphine.

boil

2 & 2 2yellow phosphorus sodium hypophosphitephosphine

)8 &5aO6 &6 O 86 #g% &5a6 8O+ + +

iv% eaction with nitric acid

8hosphorus gets o"idied by nitric acid to phosphoric acid.

) & & ) 2 2phosphoric acid

8 2$65O )6 8O 2$5O )6 O+ + +

v% Cith metals

8hosphorus reacts with metals forming phosphides. ?or e"ample

) & 2magnesium phosphide

7g 8 27g 8+

Allotropes: 8hosphorus e"ists in the following five different allotropic forms.

i% Chite #yellow% phosphorus is e"tremely reactive.

ii% Below $$/0, its vapor density corresponds to the formula 8). +bove 1'$$/0, ite"ists as 82.

iii% Kue to is low ignition temperature #Z&$/0%, it undergoes

o"idation in the presence of air which slowly raises itstemperature and after a few moments it catches firespontaneously. Kue to this reason, it is stored under water. 8 8

8

8

'ed P2osp2orus: ed phosphorus is stable allotrope at room temperature. edphosphorus is formed by heating white phosphorus in the absence of air at about 23$/0.It is not poisonous. It is safe to handle because it does not burn spontaneously at roomtemperature.

8 8

8

8

8 8

8

8

%truture of red p2osp2orus

1. Oxides:Two important o"ides of phosphorus are :

1. 8hosphorus trio"ide * 8)O, also called phosphorous o"ide or phosphorus #III% o"ide

2. 8hosphorus pento"ide * 8)O1$, also called as phosphoric o"ide or phosphorus #


29/74

Page No.->


a)Phosphorous trioxide (P4O6):

Preparation: 8repared by burning white phosphorus in limited supply of air

8)> &O2 8)O

Properties: i% On heating in air, it forms phosphorus #


30/74

Page No.-9


Oxoacids of phosphorus and their properties

Aid Nature Preparation Anion 'emars

& 26 8O or

26 8#O6%O

6ypophosphorous

crystallinewhite solid

white 8)> al!ali 92 26 8O

hypophosphite

strongly reducing,monobasic p Z 2

& &6 8O or

268O#O6%

Orthophosphorous

deli4uescentcolourlesssolid

8)Oor 80l&> 62O 9 292 & &6 8O , 68O

phosphite

reducing, but slow,

dibasic 1p Z 2

2p Z

6)82O&8yrophosphorous

white solid 80l&> 6&8O& 292 2 36 8 O

pyrophosphite

reducing, dibasic

6)82O6ypophosphoric

white solid red 8 > al!ali )92 8 O hypophosphate not reducing or

o"idiing, tetrabasic

1p Z 2

6&8O)Orthophosphoric

white solid 8)O1$> 62O 9 292 ) )6 8O , 68O ,

&9

)8O , phosphate

not o"idiing, tribasic

6)82O'8yrophosphoric

colourlesssolid

heat phosphates orphosphoric acid

)9

2 '8 O pyrophosphate tetrabasic 1p Z 2

68O&7etaphosphoric

deli4uescentsolid

heat 6&8O)to $$

+ large number of condensed phosphoric acids or their salts are !nown which have rings or chains of8O) tetrahedrally lin!ed through 8*O*8 lin!ages, e.g., di or pyrophosphoric acid, 6)82O' andtriphosphoric acid, 638&O1$.

O6 8

O

O 8

O

O6

O6O6

Triphosphoric acid

O6 8

O

O 8

O

O

O6O6

8

O

O6

O6

Kiphosphoric acid

Aodium salt of triphosphoric acid, 5a38&O1$, forms stable chelate comple"es with al!aline earth metalcations. It is, therefore, used in water softening. Chat is !nown as metaphosphoric acid and given theempirical formula 68O&is in fact a mi"ture of cyclo*polyphosphoric acids containing V8VOV8VO

V lin!ages. Two important cyclo*polyphosphoric acids are cyclotriphosphoric acid, 6&8&Oand cyclo*tetraphosphoric acid, 6)8)O12.



31/74

Page No.-91


O6 8

O

O 8

O

O6

OO

8O6 O

O

8

O

O6

cyclo*triphosphoric acid 0yclo*tetraphosphoric acid

O

8

8

O

8

OO6

O O

O6

OO6

3. Phosphine, PH3:8hosphine, 86&, is the most stable hydride of phosphorus. It is intermediatein thermal stability between ammonia and arsine.

Preparation 1. 6ydrolysis of metal phosphides such as +l8 or 0a&82:& 2 2 & 2

0a 8 6 O 286 &0a#O6%+ +2. 8yrolysis of phosphorous acid at )$ 9 )3 :

& & & & ))6 8O 86 &6 8O +

&. +l!aline hydrolysis of phosphonium iodide:

) & 286 I O6 86 I 6 O+ + +

). +l!aline hydrolysis of white phosphorus #industrial process%:

) 2 & 2 28 &O6 &6 O 86 &6 8O+ + +

8hosphine is a colourless, e"tremely poisonous gas having a faint garlic odour. +s the896 bond is not polar enough to form 896****8 or 8*6****O bonds, unli!e ammonia,phosphine is not associated in the li4uid state and is much less soluble in water. Incontrast to the basic nature of solutions of ammonia in water, a4ueous solutions of

phosphine are neutral, which is due to the much wea!er tendency of 86&to protonatein water. 6owever, it does react with 6I to form phosphonium iodide:

& )86 6I 86 I+

8ure phosphine ignites in air at about )&3 , but when contaminated with traces of826)it is spontaneously inflammable:

& 2 & )86 2O 6 8O+

Illustration - 0

H O3 42 : 0 C ( X )

( Y ) t # o $ g / ;h e a t e 1

( Z )

6 0 0 C

#%, #J% and #H% are :

#a% 6)8

2O

', 68O

&and 8

)O

1$#b% 68O

&, 6

)8

2O

'and 8

)O

1$

#c% 6)8

2O

, 6

&8O

&and 8

)8

#d% 6

)8

2O

, 68O

&and 8

)O



32/74

Page No.-9

Preparation & Properties of CompoundsAns."a$

?int : Q 2:0C 600C t#o$g/

3 4 4 2 3 4 '0heate1

H O H O HO O &

Illustration - 4

6ow many 8 9 O bonds and how many lone pairs respectively are present in 8)O

molecule

#a% 12, ) #b% , #c% 12, 1 #d% 12, 12

Ans. "$

?int : The structure of 8)O

is the number of 8 9 O bonds and lone pairs are shown. These are 12 and

1 respectivelyN.

<

Q80l

N9in solid stateN.



33/74


34/74

Page No.-90

Preparation & Properties of Compounds"iii$ )ensit8

Kensity of group


35/74

Page No.-94

Preparation & Properties of Compounds"7i$ Ioniation energ8 or ioniation ent2alp8, 6

The ionisation energies of group 2 2? O in and *1 in pero"ides22O

. Other elements of group 2, > ) and > also. The o"idations state of > ) and > being more

stable.

?or sulphur, selenium and tellurium, the o"idation states of > ) and > are important.

The > ) state is more stable for Ae, Te and 8o, then > state. This is due to the

availability of d*orbitals is the valence shells of the atoms of these elements.

"7iii$ !oleular struture "or atomiit8$

O"ygen forms stable diatomic 2O molecules, while sulphur, selenium, tellurium and

polonium are octa atomic molecules, vi, A ,Ae ,Te and 8o with puc!ered*ring

structures. The puc!ered ring structure of sulphur is shown in figure. Under ordinary

conditions, o"ygen e"ists as a gas, while all other elements of this group are solids.

Eplanation

This is because o"ygen has tendency to from p p multiple bonds. Ao, o"ygen formsa diatomic #O P O% molecule. Kue to wea! van der CaalsS forces between the o"ygenmolecules, o"ygen e"ists as a gas.

Because of their larger atomic sie, sulphur and other heavier elements of this group do

not form stable p p bonds. Ao, these elements fo not occur as diatomic molecules.Instead, A and other heavier elements of this group form 7 * 7 single bonds giving rise

to polyatomic molecule. ?or e"ample, sulphur froms ( )A octatomic molecules. Kue to

stronger van der CaalSs forces between these polyatomic molecules, these elements

#sulphur and other% e"ists as solid.



36/74

Page No.-95




37/74

Page No.-93




38/74

Page No.-9=




39/74

Page No.-9>


Illustration - >

In which of the following reactions O2is not formed as one of the product

#a% 2%$O

3Heat

=C/O #b% + + 2 3$C/ HC/ O

#c% + + 4 2 4 3FeO H O O #d% + 3* O

Ans "$

?int : Q + + +2 3 4 23$C/ 6HC/ O 3$C/ 3H O N

Illustration - 9

+cidified 7nO)is dropped over sodium pero"ide ta!en in a flas! at room temperature, vigorous

reaction ta!es place to produce

#a% hydrogen pero"ide #b% a mi"ture of hydrogen and o"ygen

#c% a colourless gas hydrogen #d% a colourless gas dio"ygen

Ans. "d$



40/74

Page No.-0


?int: + + 2 2 2 4 2 4 2 2Na O H O Na O H O & :

+ + + +4 2 4 2 4 4 22=%$O 3H O = O 2%$O 3H O :0

+ + 2 2 2 2H O O H O O & :

Illustration - 91

The structure of O&and 5

&9are

#a% linear and bent respectively

#b% both linear

#c% both bent

#d% bent and linear respectively

And "d$

?int :



41/74

Page No.-01


8otassium iodide and starch produces deeper blue colour with acidified 2 2H O

2 2 3 2H O 2H 2> > 2H O+ + + +



42/74

Page No.-0




43/74

Page No.-09


%E%1. In bleaching of delicate materials such as sil!, wool, cotton, ivory etc.2. +s a valuable antiseptic and germicide for washing wounds, teeth and ears under the name

perhydrol.&. +s [antichlorS to remove traces of chlorine and hypochlorite.

). +s o"idising agent in roc!et fuels.

Illustration - 9

+n inorganic substante liberates o"ygen on heating and turns acidic solution of I brown andreduces acidified 7nO

)solution. The substance is

#a% 6gO #b% 62O

2#c% 5O

d% 8b#5O

&%

2

And ";$

?int : +Heat2 2 2 2

2H O 2H O O ?

+ +"3i1i3

2 2 2

B#ow$

2=> H O 2=OH >

+cidified 7nO)acts as an o"idising agent when it is decolourised, 6

2O

2> O 6

2O > O

2N

Illustration - 99

Chen 62O

2 is added to ice cold solution of acidified potassium dichromate in ether and the

contents are sha!en and allowed to stand

#a% a blue colour is obtained in ether due to formation of 0r2#AO

)%

&.

#b% a blue colour is obtained in ether due to formation of 0rO3

#c% a blue colour is obtained in ether due to formation of 0rO&

#d% chromyl chloride is formed

And ";$

?int : ++ + +22 2 2 : 2

B/e o/o#i$ ethe#

C# O 2H 4H O 2C#O :H O

Illustration - 90

Chat is false about 62O

2

#a% acts both as o"idising and reducing agent

#b% two O6 bonds lie in the same plane

#c% plane blud li4uid

#d% can be o"idised by O&

And "a$



44/74

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Preparation & Properties of Compounds?int :QTwo O6 bonds lie in the different planesN

Illustration - 94

Two li4uids #+% and #B% are made of same elements and are diamagnetic. Di4uid #+% on treatmentwith I and starch gives blue coloured solution, however, li4uid #B% is neutral to litmus and does

not give any response to starch iodide paper. Ans. Q 2 2 2(") H O ; (B) H O N

Sulphur

Etration: The most important method for the e"traction of sulphur from native deposits is the?rasch 8rocess. It consists of boring a hole from the ground surface to the sulphur bearingcalcite deposit and lowering three concentric pipes to the ore bed. Auperheated water, )&, is forced down the outer pipe into the ore bed where it melts the sulphur. 0ompressedhot air is pumped down through the innermost pipe when a frothy mi"ture of molten

sulphur, water and air is forced to the surface through the middle pipe. +s it comes outfrom the well, sulphur has a purity of .39.( and virtually does not contains +s, Aeor Te.

Properties: Aulphur displays allotropy to a remar!able degree, e"isting both in a variety of differentmolecular and physical forms. The molecular species, vi., A2, A), A and A are ine4uilibrium in gaseous sulphur, their proportions varying with the temperature. Thecommon and the most stable allotrope of sulphur at room temperature is !nown as

rhombic sulphur or \*sulphur, A . In rhombic sulpur, A rings are arranged in a way that

gives a rhombic crystal structure. +t & , rhombic sulphur gets converted into

monoclinic sulphur or ]*sulphur, A . In monoclinic sulphur,

A rings are arranged in a

monoclinic structure. It is stable between & and &2 . +t &2 it melts to produce ali4uid containing Amolecules, A. +t about )&& the Arings open up and Roin togetherinto long spiral*chain molecules resulting in a thic! viscous li4uid *sulphur, A. Di4uidsulphur boils at '1 to give gaseous sulphur containing Amolecules, which dissociateto A, A), A2and finally to sulphur atoms at 22'& . If li4uid sulphur at )& is pouredinto cold water, plastic sulphur or *sulphur is formed. The allotropy of sulphur as afunction of temperature is summaried as follows:

&. B &.2 B )&& B '1 B

12'& B 22'& B

) 2

A A A A A #g% A

A A A

0old water A



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C


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Bond lengt2s and p

/ d

;onding

The bonds between A and O, or Ae and O, are much shorter than might be e"pected fro a single bond.In some cases they may be formulated as localied double bonds. + 9bond is formed in the usualway. In addition a *bond is formed by the sideways overlap of a p*orbital on the o"ygen with a d*

orbital on the sulphur, giving a p9dinteraction. This p9dbonding is similar to that found in theo"ides and o"oacids of phosphorus and is in contrast to the more common p 9ptype of double

bond found in ethane.To obtain effective p * doverlap, the sie of the d*orbital must be similar to the sie of the p*orbital. Thus sulphur forms stronger *bonds than the larger elements in the group. On crossing a

period in the periodic table, the nuclear charge is increased and more s and p*electrons are added.Aince these s and p*electrons shield the nuclear charge incompletely, the sie of the atoms and thesie of the d*orbitals decreases from Ai to 8 to A to 0l. The decrease in the sie of the &d*orbitals inthis series of elements leads to progressively stronger p*dbonds. Thus, in the silicates there ishardly any p*dbonding. Thus, AiO)units polymerise into an enormous variety of structure lin!ed

by Ai9O9Ai 9bonds. In the phosphates, 9bonding is stronger, but a large number of polymericphosphates e"ist. In the o"oacids of sulphur, 9bonding is even stronger and has become a dominantfactor. Thus, only a small amount of polymeriation occurs and only a few polymeric compounds are!nown with A9O9A lin!ages. ?or chlorine, p9dbonding is so strong that no polymeriation ofo"oanions occurs.In cases where these is more than one *bond in the molecule it may be more appropriate to e"plainthe *bonding in terms of delocalied molecular orbitals covering several atoms.

%ulp2uri aid, "?%


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Illustration - 95

Aulphur on reaction with concentrated 65O&gives #+% which reacts with 5aO6 gives #B%. #+% and

#B% are

#a% 62AO

&, 5a

2A

2O

b% 5O

2, 5a

2A

#c% 62AO), 5a2AO) #d% 62A2O&, 5a2A2O&



52/74

Page No.-4

Preparation & Properties of CompoundsAns "$

?int : + + +3 2 4 2 2(" )

6HNO H O 6NO 2H O;

+ +2 4 2 4 2(B)

H O 2NaOH Na O 2H O&

Illustration - 93

Chich of the following elements forms p*dbonding in its o"ide

#a% Dithium #b% Boron #c% Aulphur #d% 5itrogen

Ans. "$

?int :Q+mong the given elements, sulphur forms d*pbonding in its o"ides such as AO2and AO&NIllustration - 9=

0ompounds + and B are treated with dilute 60l respectively. The gases liberated are J and Hrespectively. J turns acidified

20r

2O

'paper green while H turns lead acetate paper blac!. The

compounds + and B are respectively.

#a% 5a2A and 5a

2AO

b% 5a

2AO

&and 5a

2A

#c% 5a0l and 5a20O

d% 5a

2AO

&and 5a

2AO

)

Ans. ";$

?int :QAO2turns acidified

20r

2O

'paper green.

+ + +2 3 2 4 2 4 2 2(Y )

Na O H O Na O O H O

+ + + +2 2 2 4 2 2 4 3 2 4 2@#ee$

= C# O H O 3O C# (O ) = O H O

62A turnes lead acetate paper blac!

+ +2 2 4 2 4 2(Z )

Na H O Na O H

+ +2 3 2 3H * (CH COO) * 2CH COOH&



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EE!ENT% "?A


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+ll the halogens are diatomic and e"ist as 2 2 2 2? ,0l ,Br and I . The intermolecular forces are very

wea! and their magnitude increases down the group. Thus, 2 2? , 0l are gases, bromine is a

volatile li4uid and iodine is a volatile solid.

"7$ Colour

6alogens are coloured. The colour of the halogen is due to absorption of certain wavelengths ofvisible light by their molecules resulting is the e"citation of outer electron to higher energyorbitals. ?luorine being smaller in sie absorbs shorter wavelengths corresponding to violetcolour for e"citation and appears pale yellow. Iodine on the other hand absorbs longerwavelengths corresponding to yellow colour for e"citation and therefore appears violet. In

between fluorine and iodine, the colour of chlorine is greenish yellow and of bromine is reddishbrown. Thus, the colour deepens down the group.

"7i$ Non-metalli 2arater

+ll the halogens are non*metals because of their very high ionisation energies. The non*metallic

character, however, decreases with the increase in atomic number. Iodine shows some of thedistinct metallic properties, e.g., it possesses metallic lustre and forms positive ions li!e &I , I+ +

etc."7ii$ Eletron affinities

The halogens have strong tendency to accept electrons. Their electron affinities are highest intheir respective periods. On moving down the group the electron affinity values generallydecrease with the increase in sie of the atom. The e"ception to this general rule is fluorine whichhas lower electron affinity than chlorine. It is due to the small sie of fluorine atom, the incomingelectron e"periences repulsion due to e"isting electrons in the 2p subshell resulting in low valueof electron affinity.

"7iii$


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Preparation & Properties of CompoundsAtandard eduction potential #A8%

2 2e 2 +

o o2 2? 2e 2? 2.'< F 0l 2e 20l 1.& > >

Aince A8 is the highest for 2? #among all elements of periodic table%, it is a strongest o"idising agent.

6ydration energy of

Amaller the ion, higher is the hydration energy

? 0l Br I

313 &1 &)' &$3 in !LEmolAnomalous ;e2a7iour of fluorine

The anomalous behviour of fluorine is due to its small sie, highest electronegativity, low ? 9 ?bond dissociation enthalpy, and non availability of d orbitals in valence shell. 7ost of thereactions of fluorine are e"othermic #due to the small and strong bond formed by it with otherelements%. It forms only one o"oacid while other halogens form a number of o"oacids. 6ydrogenfluoride is li4uid #b.p. 2& % due to strong hydrogen bonding. Other hydrogen halides are gases.

"i$ 'eati7it8 toards 28drogen :

They all react with hydrogen to give hydrogen halides but affinity for hydrogen decreases fromfluorine to iodine with increasing atomic number. They dissolve in water to form hydrohalicacids. The acidic strength of these acids increases in the order : 6? @ 60l @ 6Br @ 6I. Thestability of these halides decreases down the group due to decrease in bond #6 9 % dissociationenthalpy in the order : 6 9 ? ^ 6 9 0l ^ 6 9 Br ^ 6 9 I.

"ii$ 'eati7it8 toards o8gen :

6alogens form many o"ides with o"ygen but most of them are unstable. ?luorine forms twoo"ides 2O? and 2 2O ? . 6owever, only 2O? is the thermally stable at 2. These o"ide are

essentially o"ygen fluorides because of the higher electronegativity of flurorine than o"ygen.

Both are strong fluorinating agents. 2 2O ? o"idies plutonium to 8u? and the reaction is used in

removing plutonium as 8u? from spent nuclear fuel. 0hlorine, bromine and iodine form o"ides

in which the o"idation states of these halogen vary from >1 to >'. + combination of !inetic andthermodynamic factors lead to the generally decreasing order of stability of o"ides formed byhalogens, I ^ 0l ^ Br. The higher o"ides of halogens tend to be more stable than the lower ones.

Halogens

a) Fluorine

Etration: ?luorine the only practicable method of preparing fluorine gas is 7oissanSsoriginal procedure based on the electrolysis of ? dissolved in anhydrous 6?.

6e electrolysed a cooled solution of ? in anhydrous li4uid 6? at 23$ usingplatinum*iridium electrodes sealed with fluorspar caps in a platinum U*tube. Inthis reaction, the actual electrolyte is ? while 6? acts as an ioniing solvent, ?2is evolved at the anode and 62at the cathode as indicated below:

9? ?+ +

At the anode9? ? e +



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2? ? ?+

At the cathode

e + +

22 26? 2? 6+ +

7oissonSs original method has been modified. In place of the e"pensive 8tEIralloy, cells made of copper, steel or 7onel metal, which is a nic!el*copper alloy,have been used. +node is a carbon rod impregnated with copper to render it inertand cathode is made of steel or copper. + mi"ture of ? and 6? in the molar ratioof 1 : 1 or 1 : 2 is used as electrolyte.

Properties of @luorine:8ale greenish yellow gas, which is highly poisonous and having pungentodour. It is heavier than air. lectronegativity value is ).$ #8aulingSs scale%.

C2emial: 2 2 &&6 O &? 6? O+ +

2 2 226 O 2? )6? O+ +

2 &2+l &? 2+l?+

0opper does not appreciably react with ?2at this temperature because of 0u?2layer formation on it.

2 2 25aO6 2? 5a? O 26 O+ + +

2 2 225aO6 2? ? O 25a? 6 O+ + +

2 2 3I 3? 2I?+

2 2&? )6Br )6? Br 2Br?+ + +

2 2&? )6I )6? I 2I?+ + +

2 2 ) 2AiO 2? Ai? O+ +

Atrongest o"idising behaviour of ?2

& 2 2 )0lO ? 6 O 26? 0lO+ + +

2 & 2 2 2 ) 0O ? 6 O 26? 0O+ + +

2 ) 2 2 2 AO ? A O 2?+ +

C?


57/74

Page No.-43

Preparation & Properties of Compounds0u powder rare earth chloride

2 2 2)60l O 26 O 20l++ +

These methods are e"clusively used only for chlorine

Properties :

#i% It is a greenishVyellow gas with pungent and suffocating odour. It is about 2V3 timesheavier than air. It can be li4uefied into greenishVyellow li4uid which boils at 2& . Itis soluble in water.

#ii% +t low temperature it forms a hydrate with water having formula 2 20l .6 which is infact

a clathrate compound.#iii% O"idising _ bleaching properties : 0hlorine dissolves in water giving 60I and 6Od.

6ypochlorous acid #6O0I% so formed, gives nascent o"ygen which is responsible foro"idising and bleaching properties of chlorine.

#a% Ito"idises ferrous to ferric, sulphite to sulphate, sulphur dio"ide to sulphuric acid andiodine to iodic acid.

#b% 0hlorine o"idies both 2 2Br and I to Br and I respectively.

2 2 0l 20l + +

#c% It is a powerful bleaching agent F Bleaching action is due to o"idation.

2 20l 6 O 260l O+ +0oloured substance O+ colourless substanceIt bleaches vegetable or organic mather in the presence of moisture. Bleaching effect of chlome is

permanent

5ote : The bleaching action of 2AO is temporary because it ta!es place through reduction.

educed colourless material 2O of air coloured material."i7$ 'eation it2 Na


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#b% ( ) 2 & 25aO6 hot _ concentrated &0l 35a0l 5a0lO &6 O+ + +

These reactions are also given by 2 2Br and I

#v% eaction with dry sla!ed lime, ( ) 20a O6 : To give bleaching powder.

( ) ( )2 2 22 2

20a O6 20l 0a O0l 0a0l 26 O+ + +

ses : 20l is used

1. for bleaching woodpulp #re4uired for the manufacture of paper and rayon%. bleachingcotton and te"tiles,

2. in the manufacture of dyes, drugs and organic compounds such as ) &00l , 060l , KKT,

refrigerants, etc.&. in the e"traction of gold and platinum.). in sterilising drin!ing water and

3. preparation of poisonous gases such as phosgene ( )20O0l tear gas ( )& 200l 5O mustard

gas ( )2 2 2 20l06 06 A06 06 0l .

B'

#i% 0ommon method : ( )2 ) 2 2 ) ) 225aBr &6 AO conc. 7nO Br 7nAO 25a6AO 26 O

+ + + + +

#ii% ?rom Aea*water

5a0l is main component but 5aBr is also present in some 4uantity in sea water. 20l gas is

passed through sea water when vapours of bromine are evolved.

( ) ( )2 22Br a4 0l 20l a4. Br + +

The 2Br is removed by a stream of air since 2Br is 4uite volatile. The gas is passed through asolution of 2 &5a 0O when the 2Br is absorbed forming a mi"ture of 5aBr and 5aBrO&. The

solution is then acidified and distilled to give pure bromine.

2 2 & & 2

& 2 ) & 2 )

& 2 2

&Br &5a 0O 35aBr 5aBrO &0O

35aBr 5aBrO &6 AO 36Br 6BrO &5a AO

36Br 6BrO &Br &6 O

+ + +

+ + + +

+ +Properties :

#i% eddish brown li4uid, fairly soluble in water. It also forms hydrate li!e 20l

( )2 2Br .6 O 0lathrate compound#ii% est reactions are same as with 20l

I


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Preparation & Properties of Compounds2

& & )

& 2 2

2IO 6AO 2I AO 6

3I IO 6 &I &6 O

+

+

+ + +

+ + +"iii$ @rom sea-eeds:

0ertain marine plants absorb and concentrate I*selectively in presence of 0l and Br . Aea*weeds

are dried and burnt in shallow pits, ash left is called !elp. +sh on e"traction with hot waterdissolves out chlorides, carbonates, suiphates and iodides of sodium and potassium. The solutionon concentration seperates out all leaving behind iodide in the solution. Aolution is mi"ed with

27nO and concentrated 2 )6 AO in iron retorts. Diberated iodine is condensed in series of earthen*

ware !nown as aludels.

2 2 ) ) ) 2 225aI 7nO &6 AO 25a6AO 7nAO I 26 O+ + + + +

#iv% ) 2 ) 2 2 2 2 20uAO 2I AO 0uI F 20uI 0u I I+ + +

This 2I gets dissolved into I forming &I , since &I ions are yellow, therefore solution develops

yellow colour.

P'


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Page No.-5

Preparation & Properties of CompoundsThe factor, which ma!e 6? the wea!est halogen acid in water, becomes apparent if the variousthermodynamic terms are e"amined in more detail. The dissociation constant ! for the change

#hydrated% #hydrated% #hydrated%6 6 + +

is given by the e4uation:oG Tln ! =

#where $G is the Gibbs standard free energy, the gas constant and T is absolute temperature%.

6owever, G depends of the change in enthalpy 6 and the change in entropy AG P 6 9 TA

0onsider first the total enthalpy change 6 for the dissociation of #hydrated%6 into #hydrated%6+ and

#hydrated% . The 6 values for the various halogen acids are all negative, which means that energy,

is evolved in the process, so the change in thermodynamically possible. 6owever, the value for 6?is small compared with the values for 60l, 6Br and 6I #which are all similar in magnitude%. Thus,6? is only slightly e"othermic in a4ueous solution whereas the other evolve a considerable amountof heat.

The low total 6 value for 6? is the result of several factors.1. The enthalpies of dissociation show that the 69? bond is much stronger than the 690l, 69Br

or 69I bonds. Thus, the dissociation energy of 6? is nearly twice that re4uired to dissociate 6I.#The strength of the 6? bond is also shown by the short bond length of 1.$ -.

2. The heat of dehydration for the step #hydrated% #gas%6 6 is much higher for 6? than for theothers. This is because of the strong hydrogen which occurs in a4ueous 6? solutions.

&. The une"pectedly low value for the electron affinity of ?9also contributes and though theenthalpy of hydration of ?9is very high, it is not enough to offset these other terms.

?()' O6 6?2> 62O6&BO&> )6? 6B?)> &62OAi?)> 26? 62Ai?

B?&> 6? 6B?)Ba0l2> 26? Ba?2> 260l

?()'


61/74

Page No.-51

Preparation & Properties of CompoundsProperties

8hysical propertiesF 0olourless gas with pungent smell. It is heavier than air, highly soluble inwater.

C2emial properties

2 2 2 27nO )60l 7n0l 0l 26 O+ + +2 2 2 28bO )60l 8b0l 0l 26 O+ + +

2

ordinary test2 2 ' & 2 0r O 1)60l 20l 20r0l &0l '6 O+ + + +

ordinary test) 2 2 227nO 160l 20l 27n0l 3l 6 O+ + + +

& &curdy white

+g5O 60l +g0l 65O

+ +

2 & 2 2 2 &curdywhite

6g #5O % 260l 6g 0l 265O+ +

Chat happens when urea is treated with al!aline sodium hypochlorite and heated to 1$$$0

?()'

16Br > 27nO)2Br > 27nBr2> 3Br2> 62O26Br > 62AO)Br2> AO2> 262O20r2O'> 1)6Br 2Br > 20rBr&> &Br2> '62O)6Br > O2

2Br2

262O

?()' 62O 6I > 26&8O&2. 5aI > 62AO)5a6AO)> 6I

26I > 62AO)I2> AO2> 262O&. AO2> 262O > I262AO)> 26I

62AO)> BaI2BaAO)> 26IC2emial properties

)6I > O2262O > I2

'eduing Properties1. ) 2 ) 2 ) ) 2 2

8in! colourless

27nO &6 AO 1$6I AO 27nAO 3I 6 O + + + + +



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Page No.-5


2. 2 2 ' 2 ) 2 ) 2 ) & 2 2 0r O 6I )6 AO AO 0r #AO % &I '6 O+ + + + +

&. 2 2 2 26 O 26I 26 O I+ +

). 265O&> 26I I2> 262O > 25O23. & 2 22?e0l 26I 2?e0l 260l I+ + +

. ) 2 2 2 ) 220uAO )6I 0u I 26 AO I+ + +'. & 2 2 &8b#06 0OO% 26I 8bI 206 0OO6+ +eaction with I in acid medium gives the detection test I9.

2I > 262AO)2AO)> AO2> I2> 262O

'edution Propert8 of 28drogen 2alides

The stability of hydrogen halide decreased as we move down the group. The reducing property isin the order 6? @ 60ll @ 6Br @ 6I. The ease of o"idation of halide ion is e"pected to increase inthe order of increasing in the order of increasing sie of the halide ions ?9, 0l9, Br9and I9. Theelectrode to bt removed from ?9is very near to nucleus and therefore it is most difficult to

remove and easy for I9

. Therefore, 6I should be strong reducing agent

BEAC?ING P


63/74

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2 2 2 2

2 2 ) ) 2 2

2 2 & 2

0aO0l 260l 0a0l 6 O 0l

0aO0l 6 AO 0aAO 6 O 0l

0aO0l 0O 0a0O 0l

+ + +

+ + +

+ +

&65O is a strong o"idising acid to be avoided, here

E%TI!ATI

The property of halogens, that indicated incorrect is

#a% ? ^ 0l Br ^ I....... ionisation energy #b% ? ^ 0l Br ^ I....... electron affinity

#c% ? ^ 0l Br ^ I ...... electronegativity #d% I ^ Br 0l ^ ?...... density in li4uid state

Ans. ";$

?int :QThe electron affinity of 0l is ma"imum. The trend is : 0l ^ ? ^ Br ^ IN

Illustration - 0

C /2

C o / 1 a $ 1 1 i / t e N a O H

H o 1 a $ 1 3 o $ 3 . N a O H

( " ) N a C / H O2

( B ) N a C / H O2

0ompounds #+% and #B% are :NA'A(ANA )*A'+A CENT'E

1-A, )imension )urga Toer, Plot No. / 1, %etor 0 !aret, )ara Ne )el2i / 1134, P2 : 045130 6 4


64/74

Page No.-50

Preparation & Properties of Compounds#a% 5a0lO

&, 5a0lO #b% 5aO0l

2, 5aO0l

#c% 5a0lO), 5a0lO

d% 5aO0l, 5a0lO

&

Ans. "d$

?int : + + +2 2Co/1 a$1 1i/. (" )

C/ 2NaOH NaC/ NaOC/ H O

+ + +2 3 2Hot a$1 o$. (B)

3C/ 6NaOH :NaC/ NaC/O 3H O&

Illustration - 01

The property of halogen acids, that indicated incorrect is

#a% 6? ^ 60l ^ 6Br ^ 6I.......acidic strength

#b% 6I ^ 6Br ^ 60l ^ 6?.....reducing strength

#c% 6I ^ 6Br ^ 60l ^ 6?........bond length

#d% 6? ^ 60l ^ 6Br ^ 6I......thermal stability

Ans. "a$

?int :Q6I is the strongest acid while 6? is the wea!est acid. The order of acidic strength is

6I ^ 6Br ^ 60l ^ 6?N

Illustration - 0

The halogen that is most readily reduced is

#a% fluorine #b% chlorine #c% bromine #d% iodine

Ans. "a$

?int :QThe reduction potential of fluorine is ma"imum and thus, it is easily reduced, i.e., it acts asstrongest o"idising agentN.

Illustration - 09

" g C / O ( " ) ( B ) ( C ) ( + )3

% $ O H C /2

C o $ 3 .

The substances #+%, #B%, #0% and #K% are

#a% 0l2, +g0l, 0lO2, O2 #b% 0l2, +g, 0l2O, O2

#c% 62, +g0l, 6

2O, O

2#d% 60lO, +g0l, 0l

2O, O

2



65/74

Page No.-54

Preparation & Properties of CompoundsAns. "$

?int : + + +3 2 2 2(B)(") (C) (+)

2"gC/O C/ 2 "gC/ 2C/O O &



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P%E)


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Preparation & Properties of Compounds"7i$ T2ermal sta;ilit8

Thermal stability of +B type interhalogen compounds decreases with the decrease inelectronegativity difference between + and B atoms. Thus the order of stability of some +Bcompounds is asI? #1.3%^ Br? #1.2% ^ 0I? #1.$% ^ I0l #$.3% ^ IBr #$.&%^ Br0l #$.2%

In parentheses are given the electronegativity difference between + and B atoms. The aboveorder is also e"plained by saying that greater is the difference between the electronegativityvalues of + and B, the more polar is the +9B bond and hence greater is the thermal stability of+B compound.

"7ii$ 'eati7it8

+B type compounds are more reactive than 2+ and 2B molecules, since +VB bond in +B

compounds is wea!er than +V+ and BVB bonds in 2+ and 2B respectively. Thus +B type

compounds convert the metals into a mi"ture of two halides. ?or e"ample

I0l 25a 5aI 5a0l+ +The order of reactivity of some interhalogen compounds has been found as

& & ' 30l? Br? I? Br? Br?> > > > ."7iii$ ?8drol8sis

6ydrolysis gives halogen acid and o"y*halogen acid. The o"y*halogen acid is of larger#i.e., central% halogen atom. "amples are

2Br0l 6 O 60l+ #halogen acid% > 6OBr #o"y*halogen acid%

2I0l 6 O 60l 6IO+ +

& 2 2

3 2 &

3 2 &

Documents

Preparation and Properties of Compounds