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1/21/2019
1
CARBON FAMILY
C, Si, Ge, Sn, Pb
EC: ns2 np2
C : Nonmetal Si, Ge: Metalloids
S fSn, Pb: soft metals
IE: Pb>Sn (lanthanide contraction)
EA : Si > C
MP/BP: Greater than group 13 (tetrahedral network for C,Si, Ge and metallic bond for Sn/Pb)
EN values from Si to Pb almost same
CATENATION: Self linking property
C >>> Si > Ge > Sn (Pb does not show catenation as it is a metal.
C-C : 356; Si-Si : 222; Ge-Ge: 200; Sn-Sn : 150 (kJ/mole)
C: polymers ( n = several thousands),
Si: Si8H18(n=8), Ge: Ge6H14(n=6)
Sn: Sn2H6(n=2)
BONDING & OS
+2 and +4
INERT PAIR EFFECT:
The higher OS becomes less stable the lower becomes more stable down the group.
+4 state for C, Si, Ge, Sn are stable but +2 state for Pb is stable
PbCl4 does not exist at room temp.
PbO2 is unstable and strong OA
SnCl4 is stable and SnCl2 is strong RA.
EXPLANATION:
Unpairing and promotion of electron requires some energy which is provided by bond energy.
Down the group bond energy decreases and unable to provide for the excitation energyand unable to provide for the excitation energy adequately.
So the ns electron pair becomes more and more inert.
Covalent & Ionic character
• C, Si, Ge compounds : covalent
• Sn, Pb compounds in +4 state : covalent (Fajan’s Rule)
• Sn : compouns in +2 state with large sizeSn : compouns in +2 state with large size nonmetals Cl, Br, I : covalent(high polarisability)
• Sn, Pb: with F and O are ionic(SnF2, SnF4, SnO, PbO2 etc)
‐Bond Formation
• p‐p bond : C=C, C=N, C=O,
• No bond for Si, Ge, Sn due to larger size
• Why CO2 is a gas and SiO2 is a solid ?
C C
C N,
• C forms pi bonds to form discrete CO2
molecule, while Si‐O bond energy is high and forms network solid.
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d‐p Bonding in Si
• Vacant 3d orbital laterally overlaps with the filled(lone pair) orbitals of N and O
• Si – acceptor ; O/N – donors
• Not possible for Ge, Sn due to larger sizeNot possible for Ge, Sn due to larger size
• (CH3)3N is pyramidal and basic while (SiH3)3N is trigonal planar and neutral
• (CH3)3Si‐O‐Si(CH3)3 is nearly linear while corresponding C‐compound is bent
vacand d orbitalof Si
filled p-orbitalof N/O
of Si of N/O
N
SiH3H3Si
SiH3
ALLOTROPY
• C : Diamond, Graphite, Fullerene(Crystalline) (large allotropy of C is due to catenation and p‐pbonding
• Coal(natural), Coke, Charcoal, lamp black(AMORPHOUS)black(AMORPHOUS)
• Si: does not occur in free state due high Si‐O bond energy
• Crystalline: Shiny grey and brittle (semiconductor), Amorphous : brown powder(beach sand)
Allotropy(contd)
• Ge: does not exist freely
• Crystalline silvery grey
• Ge melts with decease in volume (like ice,Ga, i)Bi)
• Sn:
-Sn -Sn Rhombic Sn13.20C 1700C
greylow densitybrittle
whitehigh densitymalleable
Allotropy(contd)
• Sn : tin desease (in cold countries)
• Tin Cry : due to grating of crystal granules on each other
b bl i h hi f d ll bl• Pb : bluish white‐ soft and malleable
• turns dull grey in air due to Pb2O coating
ISOTOPES
• C: 12(98.9%), 13(1.1), 14(trace‐ radioacitve)
• Si: 28(92.2%), 29(4.7), 30(3.1) (three)
• Ge: 5 isotopes
• 70 72 73 74(most abundant) 76• 70, 72, 73, 74(most abundant), 76
• Sn : 10 isotopes(highest) 112‐124( most abundant‐120 and av. At. Mass: 119)
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Isotopes(contd.)
• Pb: 4 stable and 8 radioactive
– Stable : 204, 206, 207,208(most abundant)
OCCURENCE
• C : 17th most abundant element
• Native form: coal, diamond, graphite, fullerene
• Combined form : petroleum carbonates COCombined form : petroleum, carbonates, CO and CO2
• Si: 2nd most abundant element
• Combined state: SiO2(silica)‐ Sand, quartz etc.
Occurrence(contd.)
• Silicate minerals
• Ge : trace ( 0.1 ppm ) Germanite(GeO2), Argyrodite(GeS2), in Coal Ash, Zn/Ag ores
S C i i (S O ) i S• Sn: Cassiterite(SnO2) or Tin Stone
• Pb: Galena(PbS), Anglesite(PbSO4), Cerrusite(PbCO3)
COMPLEX FORMATION
• Carbon : no complex due to absence of vacant d‐orbitals
• Others : CN‐ 6 ( [SiF6]2‐, [SnCl6]
2‐ [Sn(OH)6]2‐ ,
[GeCl ]2‐ etc ) sp3d2 hy[GeCl6]2 etc.) sp3d2 hy.
• USES OF Si and Ge: Semiconductor devices and transistors
CHEMICAL PROPERTIES
• Reactivity: Poor RAs (low Oxidation Potentials)
• With Air: XO and XO2
• With Water : Pb does not react‐ Others withWith Water : Pb does not react Others with steam and red hot conditions. Si and Ge do not react.
• C + H2O ‐‐‐‐10000C)‐‐ CO + H2
• Sn + 2H2O(steam)heat SnO2 + 2H2
Chemical Properties(contd.)
• With Acids:
– C, Si, Ge do not react with dil. Nonoxidisingacids(HCl, H2SO4)
– Sn Pb react with dil Acids to give +2 compoundsSn, Pb react with dil. Acids to give +2 compounds
– Conc. HNO3 react with all giving NO2 and +4 oxides(C, Si, Ge), H2SnO3(Sn) and Pb(NO3)2(Pb)
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• Sn and Pb react with dil HNO3 giving N2O and +2 salts of metals.
• Pb becomes passive with H2SO4(PbSO4
coating) and with conc. HCl(PbCl2 coating)
HYDRIDES
• Carbon: alkanes, alkenes, alkynes, arenes
• Silicon : Silanes : SinH2n+2 ( n = 1‐8) : examples –Silane, disilane, trisilane etc.
• Germanium : Germanes: GenH2n+2(n=1‐6)Germanium : Germanes: GenH2n+2(n 1 6)
• Tin : Stannanes : SnH4 and Sn2H6
• Lead : Plumbane: PbH4
Thermal stability of Hydrides
• CH4 > SiH4 > GeH4 > SnH4 > PbH4
• This is due to decrease in covalent bond energy
O S S O S• HYDROLYSIS OF HYDRIDES
– Only Silanes undergo hydrolysis
SiH4 H2O H4SiO4 H2+ +NaOH
(SiO2. H2O)2silicic acid/hydrated sili
4 4
REASON:
Si has vacant d-orbital having appropriate energy to bond with H2O
REDUCING NATURE OF HYDRIDES
CH4 < SiH4 < GeH4 < SnH4 < PbH4
due to decrease in bond energy
MP/BP OF HYDRIDES:increases from CH4 to PbH4 due to
increase in V. Forces.
OXIDES
• Carbon : CO(neutral) and CO2 (acidic) C3O2, C12O9(suboxides‐ acidic)
• O=C=C=C=O (C3O2)‐Malonic acidO C C C O (C3O2) Malonic acid
• Silicon: SiO(unstable), SiO2(silica)
• CO2, SiO2 and GeO2 are acidic while SnO2
and PbO2 are amphoteric.
• GeO is acidic while SnO and PbO are amphoteric
SILICA
• 12 polymorphs
– Quartz, Tridymite, Crystobalite(common sand)
– Pure silica is colourless, glass like
– coloured due to impurity(Fe)
– 3D network structure: Each Si bonded with 4 O atoms in tetrahedral geometry and each O is bonded with 2 Si atoms (8‐membered ring network)
– Appreciable ionic character is present in each bond
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Silica(contd)
• Silica gel contains 4% H2O in the form of free –OH groups in the network structure.
• Natural Silica : Gem stones such as
A t l( hit ) (bl k/ hit )– Agate, opal(white), onyx(black/white), bloodstone, etc.
– Quartz – found in granite/sandstones(transparent) eg. flint
Propeties of Silica
• Unreactive
• Acidic oxide but does react with H2O
• Reacts with HF, F2 and alkali
SiO2 HF SiF4 H2O
SiF4 H2O H4SiO4 (SiO2. H2O) HF
+ +
+ +
SiF4 HF H2[SiF6] Hydrofluorosilicic acid
SiO2 NaOH Na4SiO4 CO2+ +
+
SiO2 NaOH Na4SiO4 CO2+ +
SiO2 F2 SiF4 O2+ +
USES OF SILICA
• Quartz : Transparent to UV/VIS. Light‐making of UV/Visible spectrometers, piezoelectric material
• Quartz: quality laboratory glass wares for low Q q y y gthermal expansion and high resistance to shock
• Silica gel : as drying agent and support for chromatography
• Kieselghur : filtration plants
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OXIDES OF Ge, Sn, Pb
• DIOXIDES
– GeO2(white), SnO2(white), PbO2(chocolate brown)
– Sparingly soluble in water
XO2 NaOH Na2XO3 H2O + +
+ +SnO2 HCl SnCl4 H2O
+ +PbO2 HCl PbCl2 H2O Cl2+
PbO2 does not dissolve or react with conc. HNO3
MONOXIDES:
GeO(brown, acidic)
SnO(blue black solid) - amphoteric
PbO(red solid) – amphoteric
MIXED OXIDES
Pb3O4(red lead) – 2PbO. PbO2
Pb3O4 HNO3 Pb(NO3)2 PbO2 H2O+ + +
brown ppt.(conc.)
SAQ
(a) PbO2/MnSO4/HNO3 (b) Pb3O4/H2SO4(dil)(c) PbO2/Cr(OH)3/KOH (d) PbCl2/NaOCl/HCl
HALIDES
• Dihalides(MX2)
• Tetrahalides(MX4)
• Upto Ge +4 state is more stable. Sn and Pbh b h 2 dshow both +2 and +4 states.
Tetrahalides
• SnF4, PbF4 are ionic solids, others are covalent liquids. PbI4 does not exist.
CX4(Carbon Tetrahalides)
• SiC + F SiF4 + C• SiC + F2 ‐‐‐‐ SiF4 + C
• CS2 + Cl2 –FeCl3/300C‐ CCl4 + S2Cl2• Inert‐ do not undergo hydrolysis due to absence of vacant d‐orbital
• (CCl4 + H2O(s.h.steam) ‐ COCl2 + HCl
Use of CX4
• solvents
• preparation of CFCs
• fire extinguisers
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SiX4
• Si + 2X2 ‐‐‐ SiX4• SiO2 + 2C + 4HCl ‐‐‐ SiCl4 + 2CO + 2H2
• Fast hydrolysis by water and alkali due to f d bi lpresence of vacant d‐orbital
• SiCl4 + 4H2O ‐‐Si(OH)4/H4SiO4/SiO2.2H2O(orthosilicicacid/hydrated silica) + 4 HCl
• SiF4 + NaOH ‐‐‐‐ Na4SiO4 + NaF + H2O
• SiF4 + 2HF ‐‐‐‐‐ H2[SiF6] hydroflurosilicic acid
GeX4
• Ge + 2X2 ‐‐‐‐ GeX4• GeO2 + HX ‐‐‐‐ GeX4 + H2O
• Hydrolyses less readily
• GeO2 + 4 H2O ‐‐‐ GeO2.2H2O + 4HX
• GeF4 + 2HF ‐‐‐ H2[GeF6]
SnX4
• Sn + 2Cl2 ‐‐‐ SnCl4• HgCl2 + SnCl2 ‐‐‐ SnCl4 + Hg2Cl2• SnCl4 is colourless fuming liquid, soluble in benzene CS2benzene, CS2
• SnCl4 + 4 H2O ‐‐‐ SnO2.2H2O + 4HCl
• SnCl4 + 2HCl ‐‐‐ H2 [SnCl6]
• SnCl4 + HCl ‐‐ H[SnCl5]
DIHALIDES
• C and Si do not form dihalides
• GeX2:
• GeX4 + Ge ‐‐‐ GeX2• Ge + 2HBr ‐ GeBr2 + H2
• GeX2 are good RAs.
SnX2
• Sn + 2HCl(g) ‐‐‐ SnCl2 + H2
• SnCl4 + Sn ‐‐‐‐‐ SnCl2• SnCl2 is a white solid, SnF2 exists as cyclic
S ( lid)tetramer Sn4F8(solid)
• SnCl2 + H2O ‐‐ Sn(OH)Cl + HCl
• white turbidity
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SnCl2 + NaOH ------ Sn(OH)2(white ppt.) + NaCl
Sn(OH)2 + 2NaOH(excess) --- Na2SnO2
(soluble) + H2O
SnCl2 + HgCl2 --- SnCl4 + Hg2Cl2 (whiteSnCl2 + HgCl2 SnCl4 + Hg2Cl2 (white ppt.)
Hg2Cl2 + SnCl2 (excess) --- Hg(grey ppt.) + SnCl4SnCl2 is bent(950) having appreciable ionic character.
SAQ
• (1)Why SnCl2 is a solid while SnCl4 is a liquid ?
• (2) Why SnCl2 is a strong RA although Sn4+
does not have high stability?
(3) h S Cl d di l i b• (3) Why SnCl2 does not dissolve in water but dissolves in Conc. HCl ?
Answers
• (1) SnCl4 has more covalent character while SnCl2 has more ionic character(Fajan’s rule)
• (2) Sn2+(aq.) ‐‐‐ Sn4+(aq.) has high SOP due to greater hydration energy of Sn4+.g y gy
• SnCl2 hydrolyses in water while forms complex with HCl
PbX2
• Pb + X2 ‐‐ PbX2• Pb(NO3) 2 + HX ‐‐‐ PbX2 + HNO3
• PbF2, PbCl2, PbBr2 – white solids while PbI2 is ld ll lidgolden yellow solid
• sparingly soluble in cold water but moderately soluble in hot water
UNIQUE PROPERTY OF CARBON
• HARDEST(diamond)• HIGHEST MP/BP• MAX OS = +4 OTHERS +6• MAX. CATENATION
HALIDES NOT HYDROLYSED EASILY• HALIDES NOT HYDROLYSED EASILY• FORMS PI BONDS• LARGE NUMBER OF ALLOTROPES• PRESENT IN ORGANIC COMPOUNDS• H2CO3 IS UNSTABLE
ALLOTROPES OF CARBON
• CRYSTALLINE
– DIAMOND
– GRAPHITE
FULLERENE– FULLERENE
• AMORPHOUS
– COAL (NATURAL)
– COKE, CHARCOAL, LAMP BLACK
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DIAMOND
• Colorless/glittering
• Black – industrial
• Hardest ( Mohs scale – 10)
• Abrasive material cutting drilling rocks and• Abrasive material‐ cutting,drilling rocks and sharpening metal tools
• Density low – 3.51 g/cc
• Thermal Conductivity – 5 times greater than Cu(disspates heat fast)
Diamond
• MP/BP – highest
• Poor conductor of electricity(lacks free electrons)
i d 0 hi• Diamond ‐‐‐‐‐‐1000C‐‐ Graphite
• Diamond + O2 ‐‐‐‐9000C‐ CO2
• High Refractive Index – gem stone
Diamond Structure UNIT CELL
FCC – ZnS type
Diamond StructureStructure of Diamond
• Infinite 3D tetrahedral network containing C‐C covalent bonds
• C‐C bond length = 154 pm.
C i 3 h b idi d• C is sp3 hybridised
• Occurrence: Igneous rocks(150Km depth)
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Artificial Diamond
• Graphite ‐‐‐‐50,000‐60000 atmpressure/16000C‐‐‐ Diamond
USES OF DIAMOND
• Jewellery( 1 carat = 200 mg)
• Abrasive
• Manufacture of tungsten filaments for l i li h b lbelectric light bulbs
• making dyes
GRAPHITE
• Occurrence: Metamorphic rocks mixed with silica and silicate minerals
• Aritificial Graphite : (ACHESON PROCESS)
i 0 / h i3C + SiO2 ‐‐‐‐‐‐30000C/24‐30 hrs‐ SiC + 2CO
SiC ‐‐‐‐‐‐25000C ‐‐ C(graphite)+ Si
Graphite Structure
2-D Hexagonal structure of each layer
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Structure of Graphite
• Parallel layers containing hexagonal 2D network (layered structure)
• Inter layer distance = 3.35 A0
h ld b k d l f• Layers held by weak Van der Waals forces
• In each layer, Carbon is sp2 hybridised
Carbon forms covalent bonds(alternate C-C and C=C) to form 2D hexagonal network structure in each layer. (C-C bond length : 1.41 A0
Each carbon atom has one unpaired electron to make pi bond.electron to make pi bond.
Extended conjugation(fused benzene rings) makes the unpaired electrons labile or free
Good conductor of electricity
Each carbon has a free electron(free radical): Dangling bond
Strucutre of unit cell
• Graphite – hcp(ABAB…..)
• Graphite – fcc(ABCABC…..)
Properties of Graphite
• Lubricating Property: sliding of loosely bound hexagonal layers
• soft, greasy grey solid
d i 2 /• density – 2.5 g/cc
• Hardness – Mohs scale : 1.5
• Soils fingers when touched
• Thermal Conductiviy – high(< dia.)
Propeties (Contd)
• Electrical Conductivity : High
• Metallic Lustre : due to free electrons
• Thermodynamic stability:
Graphite > Diamond
• Diamond ‐‐‐‐‐‐‐ Graphite + 1.9 KJ/mole
Chemical Properties
• Chemically inert but less inert than diamond
• C(graphite) + O2 ‐‐‐‐7000C‐ CO2
• Not attacked by dil. Acids/alkalies
• Forms Intercalation or Clathrate compounds: atoms• Forms Intercalation or Clathrate compounds: atoms and molecules incorporated in gaps between layers
Eg. C8M( M = K, Rb, Cs) – more conducting
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Graphite + [O] + H2O --- conc. H2SO4 ------ Graphitic acid(C11H4O3) Yellowish green
Graphite + [O] + H2O -----alk. KMnO4 --Melletic acid[C6(COOH)6 + Oxalic acid
USES OF GRAPHITE
• Making electrodes in metal extraction
• As a lubricant
• Pencil lead(black lead)
f• Brake lining and brushes for motors
• Steel making and metal foundaries
• Making crucibles
• Graphite fibres used to make light weight composites – rackets, fishing rods, aircraft parts, canoes ec.
Graphene
•Two dimensional single layer of hexagonal lattice(a polycyclic aromatic hydrocarbon(single atomic thick)• Basic unit in other allotropes•Honeycomb lattice
Graphene(contd)• Andre Geim and Konstantin Novoselovgot Nobel prize in 2010.
• It is 200 times stronger than steel.
• Conducts electricity and heat and isConducts electricity and heat and is nearly transparent.
• shows large and nonlinear diamagnetism
• Electrons have same velocity but have no mass and inertia(light)
• Electronics, semiconductor tech.
Buckminster Fullerene
• C60, C70, C76, C80, C82, C84 – Fullerenes
• Occurrence : soots, lightening discharge in atmosphere
• Black lustrous mineral – sunghites –Black lustrous mineral sunghitesC60(Russia)
• C60 – Bucky Ball
• Buckminster Fuller was a British architect after whom it was named
Discovery
• R.Curl(USA), H. Kroto(Eng). R. Smalley(USA) Nobel prize in 1996
• Discovered in 1985
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Structure of C60
• Looks like a soccer ball
• Contains 20 hexagons and 12 pentagons
• Truncated Icosahedron
• Only spherical molecule available in nature
• Contains 32 faces and 60 vertices
Each hexagon is surrounded alternately by 3 pentagons
Structure of C60
pentagons and 3 hexagons
Structure of C60
• C is sp2 hybridised. But there is no dangling bonds in it.
• 6‐6 junctions are C=C(1.39A0) while 5‐6 junctions are C C (1 43A0)junctions are C‐C (1.43A0)
• C=C bonds are largely localised
• It is a superalkene(not a superaromatic)
• Unit Cell: fcc
Preparation of Fullerene
• Graphite ‐‐‐‐‐laser beam‐ Fullerenes
Properties of Fullerene
• Thermodynamic stablity: Least
• Less stable than graphite by 38.1 KJ/mole ; less stable than diamond by 36.2 KJ/mole
• Shiny black crystals soluble in tolueneShiny black crystals, soluble in toluene, chlroform, benzene, hexane etc.
• Forms coloured solutions
Properties(contd.)
• Most symmetrical molecule
• When compressed becomes twice as hard as diamond. Henc resistant to collision
• Can accommodate molecules/atoms in the hollowCan accommodate molecules/atoms in the hollow cavity(7A0 dia.)
• K3C60(potassium buckide) super conductor
• Dissolves in water in presence of cyclic sugars called ‐cyclodextrin
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Chemical Properties
• C60 + x [H] ‐‐‐Li/liqNH3 ‐‐ C60Hx
(x=2,28,36)
• C60 + X2 ‐‐‐‐ C60 Xp (p = 2,6,8,24)
• C60 + H2O + [O] ‐‐‐‐HBO‐C60(OH)p(fullerols)
• C60 + RMgX ‐‐‐‐H3O+‐‐ R C60
USES OF FULLERNES
• Radical scavengers : prevents fowling of catalysts during petroleum fractionation
• Medical : cure parkinson diseases‐due to free radicals
L b i i Oil• Lubricating Oil :
• Catalysts:
• New polymer materials
• Insulators, semiconductors and superconductors
AMORPHOUS CARBON
• COAL (Natural)– Peat (4‐10% C)‐ used to make charcoal and compost in horticulture
– Lignite(Brown Coal)‐ 25‐35% C‐ youngest coal, used in thermal power plants
– Bituminous (soft coal) : 45‐86% used for domestic and industrial fuel
– used to make coke
Anthracite : (86-98% C)
Burns with a blue flame, used in household fireplaces
SYNTHETIC :
(1)COKE(1)COKE :
Coal ---destructive distillation-Coke is formed as residue
Used as RA in metallurgy
(2) Charcoal:
Wood/Peat/Sugar/Blood etc.----heated in limited supply of air-- Charcoal
Sugar charcoal – Purest
Wood charcoal – most impure
ACTIVATED CHARCOAL : prepared by passing super heated steam over ordinary charcoal. Used for adsorbing pollutant gases in air, water
ANIMAL CHARCOAL : used to remove colour pigments from crude sugar, oils and fats
(3) CARBON BLACK(Lamp Black or Soot)
Petroleum oil/natural gas ----burnt in limited air--- lamp black
Uses: black pigment for printing ink, shoe polish, filler in rubber and tyres
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Silicon
• Crystalline Silicon as diamond like structure.
• But the surface of silicon has some unsatisfied valence electron left free called DANGLING BONDSBONDS
SILICONES
• Silicones are long chain organo‐silicon polymers containing the following repeat unit
SiR
RO Si
R
RO
nREPEAT UNIT
SILICONE
R = alkyl or phenyl
Preparation of silicones
• Preparation of dichlorodialkylsilane
Si + 2 RCl ‐‐‐‐‐Cu/280‐3000C‐‐‐ R2SiCl2Minor Products – RSiCl3, R3SiCl, R4Si
HYDROLYSIS OF DICHLORODIALKYLSILANE AND POLYMERISATION
SiR
RClCl H2O Si
R
ROHHO HCl2 2+ +
DialkylsilanediolR R R
SiR
RO
n
SiR
OHH O SiR
OHHO SiR
OHH O+ + ++ ..................
S ILICON ES︵ n = 20 - 6,00,000 ︶
Chain length can be controlled by calculated use of R3SiCl which blocks the end.
SiOH
OH
R
R
SiHO
R
OHR
SiOH
R
OSi Si
OSi
R R
RR
CYCLIC POLYMERISATION:
OHR SiHO
R
RO RR
n = 3, 4, 5 and 6 forming 6, 8, 10- and 12 membered ring
CYCLIC SILICONE
Nature of Silcones
• n = 20 – 500 ‐ LIQUID – Silicone Oil
• n = 500 – 6000 – SEMISOLID – Silicone grease
• n = 6000 – 6,00,000 – SOLID – Silicone Rubber
• IF R‐ = Ph‐, and polymers are crosslinked –Hard Plastics
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Properties of Silicones
• Electrical Insulators, high dielectric strength
• Resistant to chemicals
• Heat resistant
• Water Repellant/nonsticky
• nontoxic
• Viscosity does not change over a wide range of temp. (due to high Si‐O bond energy)
SILICONE OIL/GREASE
• Car/shoe polish
• Oil in hydraulic pumps
• Insulator in high voltage transformers
• Cosmetic for skin (biocompatible)
• Lubricating oil in machines
• Adhesives
Silicone Rubber
• Retains elesticity over a wide range of temperature ( ‐90 – 3500C)
• Superior Endurance and reliability• Soft and wrinkle free shirts• Caps in injection vials• Caps in injection vials• Mould making materials• Rubber Products• Nipple for baby bottles• Insulators for spark plugs, anode caps, key board mats etc
SILICONE PLASTICS
• Hard as bakelites
• Electrical Insulators
• Printed circuit boards(PCBs)
• Prepared when RSiCl3 is hydrolysed and polymerised by network formation
CARBIDES
• Carbon + less EN element ‐‐‐‐ CARBIDES
• Types:
– IONIC or SALT LIKE
COVALENT– COVALENT
– METALLIC OR INSTERSTITIAL
IONIC OR SALT‐LIKE CARBIDES
• Group 1 and 2, Lanthanides and Actinides, Al from Group 13 form ionic carbides.
• Methanides: Al4C3, Be2C
• 2BeO + 3 C‐‐‐20000C‐‐ Be2C + 2CO2BeO + 3 C 2000 C Be2C + 2CO
• Al + C ‐‐‐heat‐‐ Al4C3(pale yellow)
• Predominantly ionic with covalent character
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Properties
• Al4C3 + H2O ‐‐ CH4 + Al(OH) 3• Be2C + H2O ‐‐‐ CH4 + Be(OH) 2• ACETYLIDES:
• Group 1, 2, 11(coinage metals), Zn, Cd of Gr. 12 form acetylides
• Be forms both types of carbides
ACETYLIDES(Contd.)
• CaO + C ‐‐‐‐22000C‐‐ CaC2 + CO
• Ca +2C ‐‐‐heat‐‐ CaC2• MgO + 2C ‐‐‐heat‐MgC2 + CO
• C H + 2Na ‐‐‐‐liq NH ‐‐ Na C + H• C2H2 + 2Na ‐‐‐‐liq. NH3 ‐‐ Na2C2 + H2
• C2H2 + 2AgNO3 + 2NH4OH ‐‐‐ Ag2C2 + 2NH4NO3 + 2H2O
• C2H2 + Cu2Cl2 + 2NH4OH ‐‐ Cu2C2 + 2NH4Cl + 2H2O
Properties of Ionic carbides
• transparent crystals (except Cu2C2 and Ag2C2)
• rock salt structure
• CaC2 + 2H2O ‐‐‐‐ C2H2 + Ca(OH) 2• Na C + 2H O ‐‐ C H + 2NaOH• Na2C2 + 2H2O ‐‐ C2H2 + 2NaOH
• CaC2 + N2 ‐‐‐‐11000C‐‐ CaNCN +C
The mixture is a fertiliser(NITROLIM)
CaNCN + H2O ‐‐‐‐ CaCO3 + NH3
Propynides(tricarbides)
• 2Mg + 3C ‐‐‐Mg2C3 (C34‐)
• Mg2C3 + 4H2O ‐‐‐‐ C3H4(propyne) + 2Mg(OH)2
COVALENT CARBIDES
• SILICON CARBIDE (CARBORANDUM)
• BORON CARBIDE
SILICON CARBIDE
• Acheson process (first step)
• Very hard (close to diamond)
• corrosion resistant
• high mp(22000C)• high mp(22000C)
• Pure SiC is yellowish. Often it is differently coloured due to impurites
• SiC + NaOH + O2 ‐‐‐‐ Na2SiO3 + CO2 + H2O
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SiC + 4 Cl2 ----- SiCl4 + CCl4
STRUCTURE:Diamond like structure(tetrahedral
network)
USES:
Abrasive material grinding Abrasive material – grinding, polishing and Cutting
Refractory Material – lining of furnaces
High temp. semiconductors
Ceramic material, Crucible
BORON CARBIDE
• 2 B2O3 + 7C ‐‐‐‐ B4C + 6 CO
• Properties same as SiC
• Greater electrical conductivity than SiC
• USES: Abrasive, Computer Discs, Artificial joints, Moderator in NPP
INTERSTITIAL/METALLIC CARBIDES
• TM – Group 4(Ti, Zr, Hf), 5(V, Nb, Ta), 6(Cr, Mo, W) carbides
• Refractory Carbides
• Possess all properties of metalsPossess all properties of metals
• High MP (HfC = 38900C, TaC = 38800C)
• Chemical Resistance, Hardness
• Non stoichiometric eg. MC0.9, MC0.8
STRUCTURE
• Carbon atoms occupy the holes or interstices of the metal lattice
• W + C ‐‐WC
i i• TiO2 + 2C ‐‐‐‐ TiC + 2CO
• V2O5 + 7C ‐‐‐ 2VC + 5CO
USES
• Abrasive materials
• Bullet proof vests
• rocket nozzles
• micro‐electronics
• catalysts
SILICATES
• 90% of earth crust are silicate
• O2‐ form fcc lattice and Si4+ ions occupy the tetrahedral holes. Metals ions occupy other tetrahedral and octahedral holestetrahedral and octahedral holes.
• 50% covalent and 50% ionic
• Hard, high density and refract. Ind.
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Types
• ORTHOSILICATES(NEOSILICATE/TETRHEDRAL SILICATE)
•PYROSILICATA(DISILICATE/SOROSILICATE/DOUPYROSILICATA(DISILICATE/SOROSILICATE/DOUBLE TETRAHEDRAL SILICATES)
TYPES(Contd)
• CHAIN SILICATE(INOSILICATE)
• CYCLOSILICATE(RING SILICATE)
•
SHEET SILICATES(PHYLLOSILICATES)
ORTHOSILICATES
• SiO44‐ (tetrahedral shape)
• Willemite : Zn2[SiO4], Phenacite: Be2[SiO4], Olevine: (Mg,Fe)[SiO4]
i SiOZircon : ZrSiO4
Garnets : M3M’ 2[(SiO4) 3] : M = Mg2+, Ca2+, Fe2+, Mn2+
M’ = Fe3+, Cr3+, Al3+
PYROSILICATES
• Si2O76‐
• Two tetrahedra linked by –O‐ bridge
• Hemimorphite: Zn4(OH)2[Si2O7].H2O
• Thortveitite : Sc2 [Si2O7]
SiO-
O-
O-O-
SiO4-4 ︵orthosilicate ︶
OSi
O-
O-
O-
SiO-
O-
O-
Si2O7-6 ︵pyrosilicate ︶
CHAIN SILICATE(Inosilicate)
• Single Chain Silicate (Pyroxenes)
• Double Chain Silicate (Amphiboles)
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Single Chain Silicates(Pyroxenes)
• SiO4 tetrahedra are linked with –O‐ bridge to form a polymeric chain (SiO3)n
2n‐
• Two O atoms attached to each Si are free with ‐1 charge each.
• Spodumene : LiAl[(SiO3)2],
• Enstatite: Mg2 [(SiO3) 2],
• Wollastonite: Ca3 [(SiO3) 3]:pyroxenoid group
O Si
O-
O-
O Si
O-
O-
O Si
O-
O-
O Si
O-
O-
.................
Si O
O-
(SiO )2n-
Si O
O-n
(SiO3)n
SINGLE CHAIN SILICATE(PYROXENES)
DOUBLE CHAIN SILICATES (Amphiboles)
• Two single silicates chains are crosslinked alternately by –O‐ bridges
• (Si4O11)n6n‐
li• Tremolite :
Ca2Mg5[(Si4O11)2](OH) 2(Asbestos)
• Croudolite :
Na2Fe3Fe2 [(Si4O11)](OH) 2
Properties and Uses
• Resistant to heat
• Resistant to flame and chemicals
• Strengthening cement
• Roofing sheets• Roofing sheets
• Thermal insulation
• Fibres used to make fire proof dresses
• Causes lung cancer – Silicosis, Asbestosis
O Si
O-
O
O Si
O-
O-O Si
O-
O
O Si
O-
O-O
SiO O SiO-
O-
O Si O
O-
Si
O-
O-
O
O OO- O
Si4O116-
unit
DOUBLE CHAIN SILICATE(AMPHIBOLES)
CYCLOSILICATES
• Analogous to single chain silicate but form a cyclic ring
• (SiO3)36‐ = Si3O9
6‐ (trisilicate)
• SiO3)612‐ = Si6O18
12‐SiO3)6 Si6O18
• Wollastonite : Ca3 [Si3O9]
• Benitonite : BaTa[Si3O9]
• Beryl : Be3Al2[Si6O18]
• Emerald : same as Beryl(+ 1‐2% Cr) green
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SiO-
O-
OSi
O-
O-
OSi
OSi
O- O-
Si3O96- (cyclosilicate)
SHEET SILICATES(PHYLLOSILICATES)
• Each SiO4 tetrahedron shares 3 O atoms with other three SiO4 tetrahedra to form an infinite network layer(sheet)
• Each Si is bonded to one O atom with 1• Each Si is bonded to one O atom with ‐1 charge
• (Si2O5)2‐
O Si
O-
O
O Si
O
O-O Si
O-
O
O Si
O
O-O
SiO O SiO-
O Si O SiO-
O
O O-O- O
Si O
O-
OSiO-
O
O Si
O
O-
O Si
O-
O
SHEET SILICATE : (Si2O5)n2n-
Sheet Silicates
• Kaolinite Al2(OH)4[Si2O5] – China Clay/Kaolin
• Uses: Refractory materials, porcelain cup/plate, sanitary wares
• Pyrophyllite : Al2 (OH) 2[(Si2O5) 2Pyrophyllite : Al2 (OH) 2[(Si2O5) 2• Chrysatile : Mg3(OH)4[Si2O5] – White asbestos
• Talc or soap stone : Mg3 (OH)2[(Si2O5) 2]
MICA (Sheet Silicates)
• Si4+ is partially replaced by Al3+
• [AlSi3O10]n5n‐
• Muscorite : KAl2(OH)2[AlSi3O10]
• Marganite : CaAl2 (OH)3[AlSi3O10]
• Uses : Electrical insulators in heaters, capacitors winding in furnaces, as fillers in plastics/rubber/paints
Montmorillonite(Sheet Silicate)
• (Na, Ca)(Al, Mg)6(Si4O10)3(OH)3.nH2O
• White
• Uses : Filler in plastics
• Making nanocomposites
MAN‐MADE SILLICATES:
Glass and Cement
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Tectosilicates(Framework Silicates)
• 3D network structure(Si:O=1:2) 75% earth C. SiO2 : Quartz, Tridymite, Cristobalite, Coesite etc.
• Feldspar family: Microcline‐KAlSi3O8, Orthoclase‐KAlSi3O8; Albite‐NaAlSi3O8, sodalite‐Na8(AlSiO4)6Cl2, Lazurite(Na,Ca)8(AlSiO4)6(SO4,S,Cl)2
• LAPIS LAZULI(contains Lazurite, sodalite, calcite and pyrite)a semiprecious gemstone
• Zeolites
Zeolites• Zeolites are microporous, crystalline hydrated alumiono silicates.
• Contain network of [SiO4]4‐ and [AlO4]
5‐
linked by O bridges.
A l t ili t t i hi h• Analogous to silica structure in which some Si4+ replaced by Al3+.
• The –ve charge is balanced by the presence of IA/IIA positive ions
• Natrolite‐Na2Al2Si3O10∙2H2O
• Erionite‐(Na2,K2,Ca)2Al4Si14O36∙15H2O
USE OF ZEOLITES
• Water Purification
• Softening hard water – ion exchangers
• Catalysts for cracking of hydrocarbons and i i iisomerization
• ZSM‐5(Zeolite Socony Mobil) Zeolite catalyses the conversion of ethyl alcohol to gasoline
CARBON MONOXIDE(Preparation)
CO2 + C –heat ‐‐ 2CO
CO2 + Zn ‐‐‐‐heat‐ ZnO + CO
HCOOH ‐‐‐conc. H2SO4 ‐1000C‐ CO + H2O
H C O ‐‐‐conc H SO ‐ CO + CO + H OH2C2O4 ‐‐‐conc. H2SO4 ‐ CO + CO2 + H2O
2CH4 + 3O2 (limited) ‐‐‐ 2CO + 4H2O
Fe2O3 + C ‐‐‐‐ Fe + CO
PbO + C ‐‐‐ Pb + CO
Water Gas and Producer Gas
• C(s) + H2O(steam) ‐‐‐ 1000K
CO + H2 (water gas or synthesis gas)
• 2C(s) + O2(g) + N2(g) (Air) –1273K 2CO + ( d )4N2 (producer gas)
• These are important industrial fuels.
Preparation of CO
• K4[Fe(CN)6] + 6H2SO4 +6H2O‐‐ 2K2SO4 + FeSO4 + 6CO + 3(NH4)2SO4
• Steps:– K4[Fe(CN)6] + H2SO4 ‐ 2K2SO4 + FeSO4 + 6HCNK4[Fe(CN)6] H2SO4 2K2SO4 FeSO4 6HCN
– HCN + 2H2O ‐‐‐ HCOOH + NH3
– 2NH3 + H2SO4 ‐‐‐ (NH4)2SO4
– HCOOH ‐‐‐ CO + H2O
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Properties
• Colourless, odourless, neutral
• bp = ‐1900C; mp= ‐205.10C
• Poisonous, sparingly soluble
CHEMICAL PROPERTIES
• CO + ½ O2 ‐‐ CO2 + Heat (fuel)
• RA :
• Fe2O3 + CO ‐‐ Fe + CO2
• CuO + CO ‐‐ Cu + CO2
• I2O3 + CO ‐‐‐ I2 + CO
• [Ag(NH3)2]OH + CO ‐‐ Ag + CO2 + NH3 + H2O
Chemical Properties(Contd)
• Thermal Decomposition
• 2CO ‐‐‐‐‐heat ‐‐‐ C + CO2
• Addition Reactions:CO + Cl COCl– CO + Cl2 ‐‐ COCl2
– CO + S ‐‐ COS
– CO + NaOH ‐‐‐pressure‐ HCOONa
– CO + 2H2 ‐‐‐100/200atm/300‐6000C/ZnO ‐‐‐‐CH3OH
Formation of Complexes
• Ni + 4CO ‐‐‐‐500C ‐‐ Ni(CO)4 (nickel tetracarbonyl)‐ vapour
• Ni(CO)4 ‐‐‐‐1800C ‐‐ Ni + 4CO
• Purification of Ni by Mond’s processPurification of Ni by Mond s process
• Fe + 5CO ‐‐‐‐2000C/200‐450 atm‐‐ Fe(CO)5(iron pentacarbonyl)
• CrCl3 + Fe(CO) 5 ‐‐ Cr(CO)6 + FeCl2 + CO
• CO is a sigma donor and pi‐acceptor.
Formation of Adduct
• Cu2Cl2 + 2CO + 4H2O ‐‐‐ 2CuCl.CO.2H2O
• CO is absorbed by ammoniacal Cu2Cl2
USES
• Fuel and RA in metallurgy
• Purification of Ni
• Manufacture of CH3OH, HCOOH etc
Harmful Effects:
Complexes with haemoglobin which is 300 times more stable than oxygen‐haemoglobincomplex.
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SAQ
• CO cannot be liquefied at room temperature by applying pressure like CO2. Explain.
• In metal carbonyls, M‐C bond order lies between 1 2 and C O bond order lies betweenbetween 1‐2 and C‐O bond order lies between 2‐3. Explain
ANSWERS
• 1. Critical Temp. of CO is low(subzero)
• 2. Filled 3d orbital of metal overlaps with * vacant MO of CO. So CO is a sigma donor but a pi acceptorpi‐acceptor.
CARBON DIOXIDE
• H2CO3/HCO3‐ buffer helps to maintain pH of
blood at 7.26 ‐ 7.42
• Dry ice is obtained by expanding liquid CO2
rapidly When pressure is reduced over liqrapidly. When pressure is reduced over liq. CO2, some of it evaporates and the cooling thus produced makes solid CO2.
• Sublimates : ‐ 78.50C at 1 atm.