chem chapter 22 lec

8/12/2019 Chem chapter 22 LEC

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Chapter 22

Chemistryof the

Nonmetals

2008, Prentice Hall

Chemistry: A Molecular Approach, 1stEd.

Nivaldo Tro

Roy Kennedy

Massachusetts Bay Community College

Wellesley Hills, MA


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Tro, Chemistry: A Molecular Approach 2

Nanotubes

nanotubeslong, thin, hollow cylinders of atoms carbon nanotube =sp2C in fused hexagonal rings electrical conductors

boron-nitride nanotubes = rings of alternating B and Natoms

isoelectronic with C

similar size to C

average electronegativity of B & N about the same as C

electrical insulators


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Properties of BN and C


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Main Group Nonmetals


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Atomic Radius and Bonding atomic radius decreases across the period

electronegativity, ionization energy increase across theperiod nonmetals on right ofpblock form anions in ionic

compounds

often reduced in chemical reactionsmaking them oxidizing agents

nonmetals on left ofpblock can form cations andelectron-deficient species in covalent bonding

nonmetals near the center of thepblock tend to usecovalent bonding to complete their octets

bonding tendency changes across the period fornonmetals from cation and covalent; to just covalent; toanion and covalent


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Insulated Nanowire


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Silicates

the most abundant elements of the Earths crustare O and Si

silicatesare covalent atomic solids of Si and Oand minor amounts of other elements

found in rocks, soils, and clays

silicates have variable structuresleading to thevariety of properties found in rocks, clays, and soils


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Bonding in Silicates

each Si forms a single covalent bond to 4 Osp3hybridizationtetrahedral shape

Si-O bond length is too long to form Si=O

to complete its octet, each O forms a singlecovalent bond to another Si

the result is a covalent network solid


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Quartz

a 3-dimensional covalentnetwork of SiO4tetrahedrons

generally called silica formula unit is SiO2

when heated above 1500C andcooled quickly, get amorphous

silica which we call glass


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Aluminosilicates

Al substitutes for Si in some of the lattice sites

SiO2becomes AlO2

the negative charge is countered by the inclusionof a cation

Albite = of Si replaced by Al; Na(AlO2)(SiO2)3

Anorthite = of Si replaced by Al; Ca(AlO2)2(SiO2)2


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Silicates Made of Individual Units O of SiO4picks up electrons from metal to form SiO4

4

if the SiO44are individual units neutralized by cations,

it forms an orthosilicate

willemite = Zn2SiO4

when two SiO4units share an O, they form structurescalled pyrosilicateswith the anion formula Si2O7

6

hardystonite =Ca2ZnSi

2O

7


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Single Chain Silicates

if the SiO44units link as longchains with shared O, the

structure is called a pyroxene

formula unit SiO3

2-

chains held together by ionicbonding to metal cations

between the chains

diopside = CaMg(SiO3)2whereCa and Mg occupy lattice points

between the chains


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Double Chain Silicates

some silicates have 2chains bonded togetherat the tetrahedrathese are calledamphiboles

often results in fibrousminerals

asbestostremolite asbestos =

Ca2(OH)2Mg5(Si4O11)2


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Sheet Silicates when 3 O of each

tetrahedron are shared,the result is a sheetstructure called a

phyllosilicate formula unit = Si2O5

2

sheets are ionicallybonded to metal cationsthat lie between thesheets

talc and mica


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Mica: a Phyllosilicate


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Silicate Structures


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Boron metalloid at least 5 allotropes, whose structures are

icosahedrons

each allotrope connects the icosahedra indifferent ways

less than 0.001% in Earths crust, but

found concentrated in certain areas almost always found in compounds with O

borax = Na2[B4O5(OH)4]8H2O kernite = Na2[B4O5(OH)4]3H2O colemanite = Ca2B6O115H2O

used in glass manufacturingborosilicate glass = Pyrex used in control rods of nuclear reactors


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Boron Trihalides

BX3

sp2Btrigonal planar, 120bond anglesforms single bonds that are shorter and stronger than

sp3C

some overlap of emptypon B with fullpon halogen

strong Lewis Acids


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Boron-Oxygen Compounds

form structures with trigonalBO3units

in B2O3, six units are linkedin a flat hexagonal B6O6ring

melts at 450Cmelt dissolves many metal

oxides and silicon oxides toform glasses of differentcompositions


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Boranes

closo-Boranes compounds of B and H

used as reagent in hydrogenation of C=C

closo-Boranes have formula BnHn2and formclosed polyhedra with a BH unit at each vertex


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Boranes

nido-Boranes and arachno-Boranes

nido-Boranes have formula BnHn+4consisting ofcage B missing one corner

arachno-Boranes have formula BnHn+6consisting of cage B missing two or three corners


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Carbon

exhibits the most versatile bonding of all theelements

diamond structure consists of tetrahedralsp3

carbons in a 3-dimensional array graphite structures consist of trigonal planarsp2

carbons in a 2-dimensional array

sheets attracted by weak dispersion forces

fullerenes consist of 5 and 6 member carbonrings fused into icosahedral spheres of at least60 C


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Crystalline Allotropes of CarbonDiamond Graphite Buckminster-

fullerene, C60

Color clear-blue black black

Density, g/cm3 3.53 2.25 1.65

Hardness, Mohs Scale 10 0.5

Electrical Conductivity, (mcm)-1 ~10-11 7.3 x 10-4 ~10-14

Thermal Conductivity, W/cmK 23 20 ()

Melting Point, C ~3700 ~3800 800 sublimes

Heat of Formation (kcal/mol) 0.4 0.0 9.08

Refractive Index 2.42 2.2 (600 nm)

Source Kimberlite

(S. Africa)

Pegmatite

(Sri Lanka)

Shungite

(Russia)


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Allotropes of Carbon - Diamond

Inert to Common Acids

Inert to Common Bases

Negative Electron Affinity

TransparentHardest

Best Thermal Conductor

Least Compressible

Stiffest


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Allotropes of Carbon - Graphite

Soft and Greasy Feeling

Solid Lubricant

Pencil LeadConducts Electricity

Reacts with Acids and

Oxidizing Agents


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Noncrystalline Forms of Carbon

coalis a mixture of hydrocarbons and carbon-rich particles the product of carbonationof ancient plant material

carbonation removes H and O from organic compounds in the form ofvolatile hydrocarbons and water

anthracite coalhas highest C content

bituminous coalhas high C, but high S heating coal in the absence of air forms coke

carbon and ash

heating wood in the absence of air forms charcoal

activated carbonis charcoal used to adsorb other molecules sootis composed of hydrocarbons from incomplete combustion

carbon blackis finely divided form of carbon that is a component of soot

used as rubber strengthener

All t f C b


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Allotropes of Carbon -

Buckminsterfullerene

Sublimes between 800C

Insoluble in water

Soluble in toluene

Stable in airRequires temps > 1000C to

decompose

High electronegativity

Reacts with alkali metalsBehavior more aliphatic than

aromatic


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Nanotubes long hollow tubes constructed of fused C6rings electrical conductors can incorporate metals and other small

molecules and elementsused to stabilize unstable molecules

single-walled nanotubes (SWNT) have one

layer of fused rings multi-walled nanotubes (MWNT) have

concentric layers of fused rings


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Nanotubes


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Nanocars


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Carbides carbidesare binary compounds of C with a less electronegative

element

ionic carbidesare compounds of metals with C generally alkali or alkali earth metals

often dicarbide ion, C22 (aka acetylide ion)

react with water to form acetylene, C2H2 covalent carbidesare compounds of C with a low-

electronegativity nonmetal or metalloid

silicon carbide, SiC (aka carborundum)

very hard

metallic carbidesare metals in which C sits in holes in the metallattice

hardens and strengthens the metal without affecting electrical conductivity

steel and tungsten carbide


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Calcium Carbide


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Cementite

Fe3C regions found in steel


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Carbon Oxides CO2

0.04% in atmosphere increased by 25% over the past century

high solubility in water due to reaction with water to form HCO3

ions

triple point 57C and 5.1 atm

liquid CO2doesnt exist at atmospheric pressure solid CO2= dry ice

CO colorless, odorless, tasteless gas

relatively reactive 2 CO + O22 CO2

burns with a blue flame

reduces many nonmetals CO + Cl2COCl2(phosgene) CO + S COS (fungicide)


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Carbonates

solubility of CO2in H2O due to carbonate formationCO2+ H2O H2CO3H2CO3 + H2O H3O++ HCO3

HCO3

+ H2O H3O++ CO32

washing soda = Na2CO310H2Odoesnt decompose on heating

all carbonate solutions are basic in waterdue to CO3

2+ H2O OH+ HCO32

baking soda = NaHCO3decomposes on heating to Na2CO3, H2O and CO2


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Elemental Nitrogen

N278% of atmosphere

purified by distillation of liquid air, or

filtering air through zeolites

very stable, very unreactive

NN


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Elemental Phosphorus P

white phosphoruswhite, soft, waxy solid that is flammable and toxic

stored under water to prevent spontaneous combustion

2 Ca3(PO4)2(apatite) + 6 SiO2+ 10 C P4(g, wh) + 6 CaSiO3+ 10 CO tetrahedron with small angles 60

red phosphorus formed by heating white P to about 300C in absence of air amorphous

mostly linked tetrahedra

not as reactive or toxic as white P

used in match heads

black phosphorus formed by heating white P under pressure

most thermodynamically stable form, therefore least reactive

layered structure similar to graphite


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Phosphorus

White PhosphorusRed Phosphorus


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Hydrides of Nitrogen ammonia, NH

3

pungent gas

basic NH3+ H2O NH4++ OH reacts with acids to make NH4

+salts used as chemical fertilizers

made by fixing N from N2using the Haber-Bosch process

hydrazine, N2H4 colorless liquid

basic N2H4+ H2O N2H5++ OH powerful reducing agent

hydrogen azide, HN3

acidic HN3+ H2O H3O++ N3 thermodynamically unstable and decomposes explosively to its elements


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Hydrazine


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Oxides of Nitrogen formed by reaction of N2or NOxwith O2

all unstable and will eventually decompose into N2and O2 NO = nitrogen monoxide = nitric oxide

important in living systems

free radical

NO2= nitrogen dioxide 2 NO2N2O4 red-brown gas

free radical

N2O = dinitrogen monoxide = nitrous oxide laughing gas

made by heating ammonium nitrate NH4NO3 N2O + H2O oxidizing agent Mg + N2O N2+ MgO decomposes on heating 2 N2O 2 N2+ O2 pressurize food dispensers


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Nitric Acid

HNO3= nitric acidproduced by the Ostwald Process

4 NH3(g)+ 5 O2(g)4 NO(g)+ 6 H2O(g)2 NO(g)+ O2(g)2 NO2(g)

3 NO2(g)+ H2O(l)2 HNO3(l)+ NO(g) strong acid

strong oxidizing agent

concentrated = 70% by mass = 16 M

some HNO3in bottle reacts with H2O to form NO2

main use to produce fertilizers and explosives

NH3(g) + HNO3(aq)NH4NO3(aq)


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Nitrates and Nitrites NO3= nitrateANFO = ammonium nitrate fuel oil

used as explosive in Oklahoma City

ammonium nitrate can decompose explosivelyand other nitrates

2 NH4NO32 N2+ O2+ 4 H2Ometal nitrates used to give colors to fireworks

very soluble in water

oxidizing agent

NO2= nitriteNaNO2used as food preservative in processed meats

kills botulism bacteria

keeps meat from browning when exposed to air

can form nitrosamines which may increase risk of colon cancer??


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Phosphine

PH3 colorless, poisonous gas that smells like rotting fish

formed by reacting metal phosphides with water

Ca3P2(s)+ 6 H2O(l)2 PH3(g)+ 3 Ca(OH)2(aq) also by reaction of wh P with H2O in basic solution

2 P4(s)+ 9 H2O(l)+ 3 OH

(aq)5 PH3(g)+ 3 H2PO4(aq) decomposes on heating to elements

4 PH3(g)P4(s)+ 6 H2(g) reacts with acids to form PH4+ ion does notform basic solutions


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Phosphorus Halides P4can react directly with halogens to form PX3and

PX5compounds PX3can react with water to form H3PO3PX5can react with water to form H3PO4

PCl3(l)+ 3 H2O(l)H3PO3(aq)+ 3 HCl(aq) PCl3reacts with O2to form POCl3(l)phosphorus oxychloride

other oxyhalides made by substitution on POCl3

phosphous halide and oxyhalides are key startingmaterials in the production of many P compounds fertilizers, pesticides, oil-additives, fire-retardants,

surfactants


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Phosphorus Oxides

P4reacts with O2 to make P4O6(s) or P4O10(s)get P4O10with excess O2


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Phosphoric Acid and Phosphates

H

3PO

4= phosphoric acid

white solid that melts at 42Cconcentrated = 85% by mass = 14.7 M

produced by reacting P4O10with water or the

reaction of Ca3(PO4)2with sulfuric acidP4O10(s)+ 6 H2O(l)4 H3PO4(aq)

Ca3(PO4)2(s)+ 3 H2SO4(l)3 CaSO4(s)+ 2 H3PO4(qa)used in rust removal, fertilizers, detergent additives

and food preservative

sodium pyrophosphate = Na4P2O7

sodium tripolyphosphate = Na5P3O10


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Use of Phosphates in Food


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Oxygen

2s22p46 valence electrons

stronger oxidizing agent than other 6A elements

used by living system to acquire energy

second highest electronegativity (3.5)

very high abundance in crust, and highestabundance of any element on Earth

found in most common compounds


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Elemental Oxygen O2

nonpolar, colorless, odorless gas freezing point 183C at which it becomes a pale blue liquid slightly soluble in water

0.04 g/L

mainly produced by fractional distillation of air also by the electrolysis of water

can be synthesized by heating metal oxides, chlorates, or nitrates

HgO(s)Hg(l)+ O2(g)2 NaNO3(s)2 NaNO2(s)+ O2(g)2 KClO3(s)2 KCl(s)+ 3 O2(g)

used in high temperature combustion

blast furnace, oxyacetylene torch used to create artificial atmospheres

divers, high-altitude flight

medical treatment lung disease, hyperbaric O2to treat skin wounds


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Ozone O3 toxic, pungent, blue, diamagnetic gas

denser than O2

freezing point 112C, where it becomes a blue liquid synthesized naturally from O2through the activation by

ultraviolet lightmainly in the stratosphere

protecting the living Earth from harmful UV rays

spontaneously decomposes into O2

commercial use as a strong oxidizing agent and disinfectant

formed in the troposphere by interaction of UV light and autoexhaust

oxidation damages skin, lungs, eyes, and cracks plastics and rubbers


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Sulfur

large atom and weaker oxidizer than oxygen often shows +2, +4, or +6 oxidation numbers in itscompounds, as well as 2

composes 0.06% of Earths crust

elemental sulfur found in a few natural deposits some on the surface

below ground recovered by the Frasch Process superheated water pumped down into deposit, melting the

sulfur and forcing it up the recovery pipe with the water

also obtained from byproducts of several industrialprocesses

N t l S lf D it


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Natural Sulfur Deposit


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Frasch Process


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Allotropes of Sulfur

several crystalline forms the most common naturally occurring allotrope has S8rings

most others also ring structures of various sizes

when heated to 112C, S8melts to a yellow liquid with low

viscosity when heated above 150C, rings start breaking and a dark brown

viscous liquid forms

darkest at 180C above 180C the liquid becomes less viscous

if the hot liquid is quenched in cold water, a plastic amorphoussolid forms that becomes brittle and hard on cooling


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sulfur at ~150C sulfur at ~180C


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Amorphous Sulfur


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Other Sources of Sulfur H2S(g)from oil and natural gas deposits

toxic gas (death > 100 ppm), smells like rotten eggs bond angle only 92.5 nonpolar

S-H bond weaker and longer than O-H bond

oxidized to elemental S through the Claus Process

2 H2S(g)+ 2 O2(g)2 SO2(g)+ 2 H2O(g)4 H2S(g)+ 2 SO2(g)6 S(s)+ 4 H2O(g)

FeS2(iron pyrite) roasted in absence of air forming FeS(s)and S2(g)

metal sulfides roasted in air to make SO2(g), which is later reduced react with acids to make H2S

most insoluble in water

used as bactericide and stop dandruff in shampoo


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Metal Sulfides


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Sulfur Dioxide SO2

colorless, dense, acrid gas that is toxicproduced naturally by volcanic action and as a byproduct of

industrial processes including electrical generation by burning oil and coal, as well as

metal extraction

acidic

SO2(g)+ H2O(l)H2SO3(aq) forms acid rain in the air

2 SO2(g)+ O2(g)+ 2 H2O(l)2 H2SO4(aq) removed from stack by scrubbing with limestone

CaCO3(s) CaO(s)+ O2(g)2 CaO(g)+ 2 SO2(g)+ O2(g)2 CaSO4(g)

used to treat fruits and vegetables as a preservative


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Sulfuric Acid

most produced chemical in the world strong acid, good oxidizing agent, dehydrating agent

used in production of fertilizers, dyes, petrochemicals,paints, plastics, explosives, batteries, steel, anddetergents

melting point 10.4C, boiling point 337C

oily, dense liquid at room temperature reacts vigorously and exothermically with water you always oughter(sic) add acid to water


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Dehydration of Sucrose

C12H22O11(s)+ H2SO4(l) 12 C(s) + 11 H2O(g) + H2SO4(aq)


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Production of H2SO4

contact process step 1: combustion of elemental S complete using V2O5catalyst

S(g)

+ O2(g)

SO2(g)

2 SO2(g)+ O2(g)2 SO3(g) step 2: absorbing the SO2into conc. H2SO4to form

oleum, H2S2O7

SO3(g)+ H2SO4(l)H2S2O7(l) step 3: dissolve the oleum in waterH2S2O7(l) + H2O(l)2 H2SO4(aq)


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Halogens

most reactive nonmetal group, never found inelemental form in nature come from dissolved salts in seawater except fluorine, which comes from minerals fluorospar

(CaF2) and fluoroapatite [Ca10F2(PO4)6] atomic radius increases down the column most electronegative element in its period, decreasing

down the column

fluorine only has oxidation states of -1 or 0, othershave oxidation states ranging from -1 to +7


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Properties of the Halogens


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Fluorine F

2

is a yellow-green toxic gas

F2is the most reactive nonmetal and forms binary compoundswith every element except He, Ne, and Ar including XeF2, XeF6, XeOF4, KrF2 so reactive it reacts with other elements of low reactivity resulting in

flames

even reacts with the very unreactive asbestos and glass stored in Fe, Cu, or Ni containers because the metal fluoride that forms coats

the surface protecting the rest of the metal

F2bond weakest of the X2bonds, allowing reactions to be moreexothermic

small ion size of F

leads to large lattice energies in ioniccompounds

produced by the electrolysis of HF


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Hydrofluoric Acid HF

produced by the reaction of fluorospar with H2SO4CaF2(s)+ H2SO4(l) CaSO4(s)+ 2 HF(g)

crystalline HF is zig-zag chains

HF is weak acid, Ka= 6.8 x 10-4at 25C

F can combine with HF to form complex ion HF2

with bridging H strong oxidizing agent

strong enough to react with glass, so generally stored in plastic

used to etch glass

SiO2(g)+ 4 HF(aq)SiF4(g)+ H2O(l) very toxic because it penetrates tissues and reacts with internal organs and

bones

Halogen Compounds


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Halogen Compounds form ionic compounds with metals and molecular compounds

having covalent bonds with nonmetals

halogens can also form compounds with other halogenscalledinterhalides for interhalides, the larger has lower electronegativityso it is central in the

molecule; with a number of more electronegative halides attached

general formula ABnwhere ncan be 1, 3, 5, or 7most common AB or AB3; only AB5has B = F, IF7only known n= 7

only ClF3used industrially to produce UF6in nuclear fuel enrichment

most halogen oxides are unstable tend to be explosive

OF2 only compound with O = +2 oxidation state

ClO2(g)is strong oxidizer used to bleach flour and wood pulp explosiveso diluted with CO2and N2

produced by oxidation of NaClO2with Cl2or the reduction of NaClO3with HCl

2 NaClO2+ Cl22 NaCl + 2 ClO22 NaClO3+ 4 HCl 2 ClO2+ 2 H2O + 2 NaCl

chem chapter 22 lec

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