Class Note for CHM 218 with Professor Berger at IPFW
Class Note for CHM 218 with Professor Berger at IPFW
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151 Chapter 15 e The Grnup 15 Elements Group 15 eonsrsts of two very dusxmxlarnonrmetals N and P a Elzmem m p c b p c semkmetal As andtwo weakmeta1s Sb andBr NandP are N am 49o both e1eetnea11y nonrconducung andhave aerate omdes and are p 44 m therefore classx ed as nonrmetals As has allotxopes that have As subumesrtots metanre and nonrmetalh appearanee and forms an amphotene omde Sb ande form an amphotene and basre omde 5 7 53 37 respeetve1y The deerease m m p wrth rnereasrng z and the long E1 271 1564 hqurd range para11e1 those of other mam goup metals Annmalnlls Nature or N39m39ngen There 15 httTe resemb1anee between mtxogen and the rest of the members ofthe farmly apart from storehrometry The NNmple bondrs abnormany strong whr1e the NrN stng1e bond 15 abnormauy weak As aresu1tN orms the dratomre mo1eeu1e N2 rather than eatenatang as c does The abnormany hgh NNbond suength a1so favors the formataon of damtxogen m a number of ehemrea1 reaetaons The NO bond strength 15 a1so eonsrderab1y weaker than the 0 bond strength NaHngH 0 9 Nan 2H20 CaHngH30 9 2C02Cg 2H20 Unhke Group 14rn Groups 15 and 16 the seeonde1ement m the famxly P and srespeetane1y has the greater propensrty to eatenataon Nforms only the tn uonde NE unhke P whreh forms a tn uonde PF and a penta uonde PP The best exp1anataon for thrs observataon 15 thatN 15 too sma11 to aeeommodate more than 3 F atoms whr1e P 15 suf mendy large to aeeommodate 5 F atoms The argument that P has d orbrta1s avar1ab1e whr1e N does not 15 weak srnee d orbrta1s neednot be rnvokedto prode a M o desenptaon ofPFr or other hypervalmt or expanded oetetquot mo1eeu1es Both N and P form a eompound ofthe formula sto In FXNO the Nr 0 bond 15 qurte weak Whlle m FZPO the P o bondrs qurte strong In FZPO the assumptaon 15 that there 15 eonsrderab1e double bond eharaeter m the P 0 bond whreh 15 not as easr1y rataonahzed m FZNO pK 152 The greater electronegativity of N also results in anomalous behavior The polarity of bonds in nitrogen compounds is o en the reverse of those in the analogous compounds of the heavier elements of the family NC13 0 3 H20 0 a NH3 g 3 HClO aq PC130 3 H20 0 a H3 PO3 aq 3 HCl g The greater polarity of the N H bond in ammonia results in ammonia being basic whereas phosphine PH3 aisine AsH3 and stibine SbH3 are all essentially neutral Nitrogen Nitrogen does not exhibit allotropy Its only stable form is the colorless odorless diatomic gas N2 N2 comprises about 78 of our atmosphere Nitrogen is also found in naturally occurring nitrate deposits N aNO3 Chile saltpeter On an industrial scale N2 is obtained by the fractional distillation of liquid air On smaller scales it can be obtained using a zeolite to separate it from other atmospheric gases or by the thermal decomposition of ammonium nitrite or sodium azide NH4N02 aq a N2 g 2 H20 0 2 NaN3 s a 2 Na s 3 N2 g N2 is fairly unreactive at room temperature but its reactivity increases at elevated temperatures At room temperature N2 reacts with Li 6 Li s N2 g a 2 Li3N s as well as with some transition metal complexes where N2 is a weak ligand At elevated temperatures a number of other reactions are possible including reaction with alkaline earths other than Be 3 M S N2 g M3N2 S It also reacts with 02 in the atmosphere when initiated by a lightning ash or in internal combustion engines N2 g t 202 v 2 N02 g 153 It reacts wnh H2 9 to proahee an equrhbnurr rmxmre ofNE g under appropriate conditions Nag3Ha ZN39Hng Overview nfNitrngEn Chemistry 7 Arm mam mm Bawiiandmom The chermstxy of mtxogen rs complex and mtxogen assumes oxidanon states from 510 r3 The 2 N0 relaaye stabxhty othe vanous oxrdaaor states 2 1 MO depends on pH gt r a 2 1 Molecular nitrogen N2 rs hermedyrrameauy g Y very stable as rs the ammmrurr mnNE r g mm L 5m 2 The oxoamds HNo3 and HNo1 are very Fxgnn 5 Frasrmapram u seed mans same however m base 3232er soluaorr No and NO are mueh Weaker oxrdrzrng agems 3 1r basre soluaorr hydroxylarmne NHZOH hydrazan NH and ammoma NE are all redunng agems m basre solution 4 Hydroxylamne ande hydroxylammomaum rorr NHsorr are both unstable wnh repent to dispropomonanon 3 NHon aq N2 g N39H aq 3Ha0 l 4NH30H aq N20 g 2 NH aq 2H aq 3Hzo a Ammunia Ammpma rs a colorless toxic gas wnh aprererng charactensm odor It rs a weak base and the only common gas whreh rs base NH aq HZO a NTL aq OH39 aq Ammpma ear be prepared by heaang a rrrrxmre of an ammonium salt and a hydrode 2 N39H l s CaOH2 s a 2 NH3 g Cacl1 s 2 H20 1 15 4 Reamons ofAmmoma Arnrnonra bums m nr to gve Waist and erdnerN2 or No dependmg on condmons N rs me unerrnodynarnredly preferred predict however m are presenee of a pladnurn catalyst NO rs me krneneauy preferred prode 4NHg30 2NgoHoa AG 713mm 4NHg50 4NOgoHoa AG 71132kJ NH undergoes two 6433an reaenons wrun emonne Wrun Excess NH N2 rs prodreed and me Hag that rs produeedreans wrun the excess NH to produce so1rdNHc1 2NHg3c1e N6Hc1 NH2 HCI NTLCMS Wrun Excess ch Nc1 rs uneprodun NHg3c1e NC1I3HCI NH reacts wrun Brmsted ands to form the arnrnonrurn ron NH NH aq HNo aq NHNO aq NH can an as a Brmsted and m are presenee of ememely strong bases to produee me amde ron NH N39H am CH am CE am N39Hz39 am Propnnes ofAmmoma 39 H Arnrnonra has an abnormally mgr bodmg point 7 35 C comparedto phosphme PH b p 7 134 C due to hydrogen bondng It rs yery soluble m Waist 50 g per 100 mL n 40 oo 30 1 qula wel l 155 quulol ammorua ls a polar solvent and undergoes autororuzataoh 2 NH l NTL am NH am Ammoruals a strong Levvls base by vlrtue oflts lohe pm and reaets Wth Levvls bases sueh as BF as vvell as Wth trmsltaoh metal lohs N39H 9 BF 9 HNr BF 5 N1HzOr W 6 IN39Hz aq NxNTLr 6 H20 1 Haber Proeess The reaetaoh ofN and H to prooluee NH ls an equlllbnum that mvolves a trade off between thermodynamles and kmencs Ng3H2 2N39H AS r1991 Kquot Beeause ofthe slgls of AH and AS AG becomes less hegauve athbeeomes smaller asthe temperature mereases Beeausethe reaetaoh mvolves a deereasem volume LeChateher39s Puhuple suggests that the equlllbnum shoulol be more favorable at htgr pressure E Hovvever reasonable reaeuoh rates are only aehleveol at lt hlgrer temperatures Fntz Haber drseovereol that a W reasonablevlelols eoulolbe achlevedln areasonable ume Prersurrtmu net 5 petsemeee yuehs at uslng apressure of 200 atm and a temperature of am as 5 mm m Drama 500 C at vavmus tempetalutes Uses of Ammoma The most lmportarrt use of ammomals m the femllzer molustrv Ammoma em be appheol drreetlv to elds as agas anhydrous ammorua or as asoholm theme of ammoruum sulfate or ammoruum phosphate 2 NH 3 HZSOO aq NE 50 ma 3 NH 3 190 aq NE PO aq 156 The Ammonium Ion The ammonium ion is colorless the most common nonmetallic cation used in chemistry Its geometry is tetrahedral and is considered a pseudoallmli metal cation with a radius close to that of K Although it is a pseudoalkali metal cation it undergoes reaction which do not occur for allmli metal ions NH4 can be hydrolyzed NHI 211 H20 0 NH 211 H30 211 it can dissociate 2 NH4C1 s 1 NH3 g HCl g or it can be oxidized as when some of its salts undergo thermal decomposition NH4N02 211 N2 g 2 H20 0 NH4NO3 s a N20 g 2 H20 0 NH42CT207 5 N2 g CT203 S 4 Hz0 g Other Hydrides of Nitrogen Hydrazine 039 Hydrazine is afuming colorless liquid It is a weak difunctional quot39 H base IN N H39 l H NZH4 aq H3O aq a NZH aq H20 0 N2H4 aq 2 H3O aq a N2H52 aq 2 H20 0 Hydrazine is also a potent reducing agentwhich reduces 12 to H1 and Cu to Cu NZH4 aq 2 I2 aq a 4 HI aq N2 g N2H4 aq 2 Cuzl aq H 2 Cu s N2 g 4 PF aq l 5 7 Hydrogen Azide Hydrazoic Acid Hydrogen azide is a colorless acidic liquid with a pKa of 19 X 10395 making it about as strong as acetic acid Although formally a hydride of nitrogen it bears no relationship to ammonia or hydrazine HN3 211 H20 0 N3 211 t H30 211 The liquid is highly toxic with an extremely disagreeable and irritating odor It is explosive and decomposes to H2 and N2 2 HN3 0 H2 g 3 N2 g The free acid can be obtained in solution by the reaction N2H5 211 HN02 211 HN3 211 H 211 t 2 H20 0 The terminal NeN bond length is 113 pm between the length ofa 124 Pm 113 pm typical NN bond 120 pm and that of the NEN bond in N2 110 pm 7 N N and the interior NiN bond length is 124 pm between that of the NeN bond length in hydrazine 147 pm and that of a typical NN bond 120 0 pm This can be rationalized with the following resonance structures 110 N N lt gt 3 H H The azide ion N3 is isoelectronic with C02 and the NeN bonds are equal in length 116 pm It is o en considered a pseudohalide 39 39 NN N The decomposition of sodium azide NaN3 is the reaction that causes quot quot automotive airbags to in ate rapidly 40 ms 2 NaN3 s a 2 Na 9 3 N2 g The sodium metal is then immobilized in a series of reactions which result in the formation of glassy silicates 10 Na 2 KNO3 s a K20 s 5 NaQO s N2 g 2 K20 s sro2 s K4Si04 s 2 NaZO s sro2 s Na4SiO4 s 158 Sodium azide can be prepared from sodium amide NaNHz by diiTerent routes 3 NaNH2 NaNO3 a NaN3 3 NaOH NH3 2 NaNH2 N20 4 NaN3 NaOH NH3 Azides of PbII and HgII are used as a shock sensitive detonators in blasting caps P DN32 S Pb S 3 N2 g Hydroxylamine Hydroxylamine NHZOH is a weak base much weaker than ammonia NHZOH aq H20 0 e NH3OH aq OH39 aq Kb 66 x 10399 It is prepared by the reduction of nitrates or nitrates either electrolytically or with 02 under controlled conditions Hydroxylamine is an unstable white solid In aqueous solution or as one of its salts eg NH3OHCl or NH3OHSO4 it is used as a reducing agent NOx The Oxides of Nitrogen Nitrogen forms an array of oxides in a variety of oxidation states Compound AG k Jm01 1 Each of these is thermodynamically unstable with respect to the elements but exists by virtue of kinetic stability Collectively the N20 g 104 oxides of nitrogen are referred to as NOX NO g 87 N 203 g 139 Dinitrogen Oxide nitrous oxide N 02 g 51 N20 is used as an anaesthetic sometimes called laughing gas NZO4 g 98 as well as a propellent for pressurized cans of whipped cream because of its solubility in fats and the fact that it is taste free N205 g 115 and nontoxic It is a fairly unreactive neutral gas which supports combustion Mg S N20 g MgO S N2 g It is also an effective electron scavenger in radiation chemical studies 6 211 H20 9 N20 211 a N2 g OH 211 0H 211 159 N20 15 preparede me unenna1 decomposmon ofrnouen NENO or more safely by are unenna1 decomposann of an and solution of NENO NTLNO aq N20 g 2 H20 1 N201sxsoelectxomcthh cq and Nbut has an asymmem structure The N o bondrs mta medwte m 1engun between a smgle and double bond whde are N Nbond 15 mtermedaate m 1engun between adouble and mplebond We can ranonahze Lhs obsa39vanon wrun are followmg resonance structures NEMQ H NNO Nxtxogen Mononde mm ornate Nxtxogen monoxide 15 a colorless neutral paramagnetic gas 115 pamal MO dAagram 15 srrnr1ar to that of co however wrun one addmonal electron whmh must resrde m an annrbondmg orbxtal1ts bond order 15 212 The mgr Energy 313mm m the v orbnal 15 readily 1051 to form are very stable mkosyl 1mNO39 whmh 15 xsoelectxomc wrun co The bond order 15 3 and enmer 106 pm than are bondm NO 115 pm ere co NO forms a vanety ofcomplexes wrun metals pamculady those m low oxxdanon states Deme the fact that r has an unpnred electron r 15 farly gable and 61mmzes to N202 only at low temperatures N015 reaenve toward q andrs oxxdazedto Nq 2N0g02 2NOZ 11 15 formed as a byrproohd m the combustion ofgasolme m mtemal combusnon engmes where are compressed gas rnnrmre contams both N2 and q Nng Oz 2N0g NO can be formede are reamenon of 50 HNo3 by O 3 015 8 111103 aq a 3 CuN032 aq 4Hzo 1 2 NO g 1 5 10 Dinitrogen Trioxide Dinitrogen trioxide N203 is the least stable of the common oxides of nitrogen with A 13 139 1d 39 mol39 1 It is prepared by condensing stoichiometric quantities of NO and N02 N0 N02 g x N203 0 It is an intensely blue liquid which solidi es to a pale blue solid at 102 C Decomposition to NO and N02 is signi cant even at 30quotC N203 a N0 g t N02 g The liquid appeals to undergo autoionization N203 Q 1 NOJr solv N027 solv N203 is the fust of the acidic oxides of nitrogen and is formally the anhydride of nitrous acid HNOZ N203 0 H20 0 2 HN02 aq N203 0 2 OH39 aq 2 N0239 aq H20 0 The structure is asymmetric with an abnormally long NiN bond length of 189 pm Recall the NiN single bond in hydrazine is about 146 pm The odd 0 to N bond is shorter than the other two consistent with the resonance structures shown 189 121 pm 0 o o o P o N N lt gt N N O O 112 pmN N D 1286 DU 0 o Nitrogen Dioxide and Dinitrogen Tetraoxide 105 These two oxides exist in a strongly temperature dependent equilibrium 0 O O N N 2 39 N AH 57 kJmol O O O colorless red brown 15 1 1 The solid is colorless but the equilibrium constant increases with increasing temperature The liquid is pale yellow at the freezing point 11 C due to 001 N02 At the boiling point 212 C the liquid is deep redbrown and contains about 01 N02 At 100 C the vapor is about 90 N02 and dissociation is complete above about 140 C N02 can be prepared by the reduction of concentrated nitric acid with Cu Cu s 4 HNO3 aq a CuNO32 aq 2 H20 0 2 N02 g the thermal decomposition of metal nitrites CuN032 S v 0110 S 2 N02 g 12 02 g or heavy metal nitrates 2 PbNO32 s a 2 PbO s 4 N02 g 02 g or by the oxidation of NO by 02 2 N0 g 02 g x 2 N02 g N02 is another acidic oxide which dissolves in water to form a mixture of nitric acid and nitrous acid and is a major contributor to acid rain 2 N02 g H20 0 1 HNO3 aq HNO2 aq O The ONO angle in N02 is 134 somewhat larger than the 39 Nltgt 13 4o ideal trigonal planar angle of 120 This is consistent with a 0 single unpaired electron requiring less space than shared pairs of electrons The OiNi 0 angle in N204 is virtually identical 175 pm but the NiN bond length is again abnormally large at 175 pm with a bond energy of only about 57 ld39mol39l O o N N 1338 0 j 1512 Dinittogen Pentaoxide Dinitrogen pentaoXide is a colorless deliquescent solid which is the anhydride of nitric acid N205 s H20 0 a 2 HNO3 aq In the liquid and gas phase the molecule has a structure similar to N204 with an O 14939 8 pm atom between the two N atoms but the 0 solid is actually an ionic substance 0 118 8 m formulated as N02NO339 The No 1 3 3 2 NltON p cation is called the nitronium ion and is g 11 1 80 O isoelectronic with C02 N20 and N31 0 Z O N 25 0 N205 is formed by the dehydration of HNO3 by P205 2 HNO3 P205 4 HPO3 N205 or by the interaction of FN02 with LiNO3 FNO2 LiNO3 a N205 LiF The Nitrate Radical The nitrate radical is formed by the reaction of N02 with ozone N02 g 03g N03g 02 and is important in nighttime atmospheric chemistry In daylight it is photolyzed to NO or N02 N03 9 No 9 02 9 N03 9 L Now 09 1513 In the absence of light it reacts with allmnes or alkenes in the environment to form strongly oxidizing products Q 9R H9 quotR9 FNOs 9 Nitrogen Halides Nitrogen trichloride NC13 is an oily yellow liquid as is characteristic of covalent chlorides It undergoes hydrolysis to ammonia and hypochlorous acid N013 aq H20 0 NH3 g 3 HClO aq These products are consistent with the expected polarity of the 6 TI 6 N 7 C1 b d 39 on C I NH The compound is explosive when pure but the vapor is used AF OH industrially as a bleaching agent for our 6 6 Nitrogen tri uoride NF3 is a thermodynamically stable colorless odorless gas of low reactivity and is stable to hydrolysis Unlike NH3 it is a poor Lewis base and has FiNiF bond angles of about 102 This is consistent with Bent s Rule which suggests the hybrid orbitals used in bonding to F are high in p character and the orbital in which the lone pair resides is high in s character NF3 reacts with 02 gas at low temperature to form a compound with a coordinate covalent bond between N and O FquotINO I F 2 NF3 g t 02 g A 2 FsNO g Nitrous Acid and Nitrites Nitrous acid is a weak acid that can be prepared by the action of a strong acid on a nitrite salt BaN022 aq H2804 aq a 2 HN02 aq BaSO4 s It is unknown in the liquid state but has been observed in the gas phase In solution it undergoes slow disproportionation at room temperature and the rate speeds up at elevated temperatures 3 HNO2 aq HNO3 aq 2 NO g H20 0 1514 The nitrite ion is an oxidizing agent which is capable of oxidizing many common ions including Fe and I39 HNO2 aq H aq e39 a NO aq H20 0 EO 10 V As a result nitrites of metals in low oxidation states cannot be prepared Sodium nitrite is used as a preservative for fresh and cured meats because it inhibits the growth of bacteria When used with fresh meat it oxidizes hemoglobin to methemoglobin which resists oxidation Nitric Acid and Nitrates Nitric acid is a colorless oily liquid when pure and is extremely hazardous It is a strong acid as well as a strong oxidizing agent Although colorless when pure the acid may appear yellow due to trace NO2 which results from photolytic decomposition 11 4mm 4mz022uol The pure liquid undergoes slight autoionization 3 HNO3 a e NO HNO3 H3O HNO3 2 N03 HNO3 Concentrated nitric acid is a 70 aqueous solution which is about 16 M in HNO3 Fuming nitric acid is an extremely potent oxidizing agent and is a red solution of NO2 in pure HNO3 The rst industrial synthesis of nitric acid used a mixture of N2 O2 and water in an electric arc fumace to produce HNO3 directly The arc lmace was needed to overcome the large activation banier 2N2g502g 2H20g 4HN03g Fortunately this banier exists Ifnot for it our atmosphere would have high HNO3 concentrations and our lakes and oceans would be nitric acid Today the Ostwald Process is used to prepare nitric acid 4 NH3 9 5 029 gt 4 N0 9 6 H20 9 2 NO 9 02 9 2 N02 9 3N02 9 H20 I gt 2HN03 I NO9 The tammal NaObonds m HNO3 are shorter 121 pm than the Na 0711 bond 141 pm but an three bonds m he nmate 1m are equal m 1eng1h 122 pm Nxtxates of most metals m eommon oxldanon gates are known and are so1ub1e makmg these salts 141m convement sources of a vanety of cations The Nnxaee 1m 15 strongly omdamg oh1y m and sohmon so mtxates ofmetals mloweroxxdanon states can be 1so1azede g FeNO2 o The men 1mponantmtxate mobsmauy 15 ammomum mtxate whmh ean be obtanedby reacting ammoma wnh mm and 122 pm N39H aq HNO aq NTLNOZ aq NTLNOZ 15 usedm eo1d packs beeause the dassolunon ofNENO 15 endothermm NTLNOZ s N39Ha aq No aq AH 2s kl AS 110 1Kquot NTLNOZ 15 a1so used as a femhzer but muSL be handled wnh care beeause 11 deeomposes exp1os1ve1y at hgher temperatures NTLNO3 s a 2 H20 g N20 9 2NH4N025quot2N230134H20 thsphnnls Chemistry Unhke mtxogEn the hgher omdanon gates of phomhoms are the most gable wh1e the Iowa oxxdanon states are least stable Wh1le mm and 15 a strong oxldamg agem phosphone ambs not The eonaascs are obmous from the Frost dagam for the two elemems 2 1 11 a1 a a xuhniun mm 1516 Allotxopes of Phomhoms Phosphorus has several allotxopes whlte red and bl aek phosphorus The slmplesL and least gable ls whlte phomhoms sorneurnes ealled yellow phosphorus Whue phomhoms ls ahlghly wxm whlte waxy solld oeeumng as P tetrahedra heldtogether by weak dlsperslon forces As aresult n has alow rnelung pomt 44 C Whue phosphorus ls eruernely reaeuye due to the hlghly stained bonds m the P tetrahedra Ills montaneously ammablem arr and must be stored underwater Ills solubleln eornrnon nonepolar sellants P s 5 O 9 Psoln 5 When whlee phosphorus ls exposed to uluawoln llght u undergoes a slow rearrangement to redphosphorus where one ofthe Pep bond m P ls broken and adjacent tetrahedra are lmked by a slngle bond Redphosphoms ls lherefore polyrnene and less saarnedrn nature Redphosphorusrs stablem arr and reacts dlrecdy wuh q only at elevatedtemperatures The rnelung pmnt of red phosphorus ls 600 C where the eharns break to yleldrndyldual P unlts Red phomhomsls lnsolubleln eornrnon solvents The moSL stable form ofphomhoms ls blaekphosphorus whreh ls also the most dlfflcult to prepare Blaek phosphorus has a complex polyrnene structure shown below andls prepared by heaung whlte phosphorus under exuerne pressure 1517 Extraction of Phosphorus Phosphorus is prepared from naturally occurring calcium phosphate Ca3PO42 in an energy intensive process 180 000 A 500V and 1500 C 2C03PO4251OCO A accocs 10 oogs P4ltg Compounds of Phosphorus Phosphine Phosphine PH3 is a colorless extremely toxic gas Unlike ammonia phosphine is sparingly soluble in water and an extremely weak base The P H bonds are much less polar and phosphine is incapable of hydrogen bonding It can be prepared by combining an active metal phosphide with water or dilute acid Ca3P2 s 6 H20 0 a PH3 g 3 CaOH2 aq The HiPiH bond is only 930 compared to about 1070 for the HiNi H bond P in ammonia This suggests that phosphorus uses pure p orbitals rather than sp3 H quotH hybrid orbitals for bonding to H The lone pair is essentially in the s orbital H Phosphine itself has limited utility but substituted alkyl and aryl phosphines are IllP Pmquotl common in coordination chemistry H30quot I CH2CH2 39CHS H36 CH 3 dmpe Oxides of Phosphorus Phosphorus forms two molecular oxides representing the 3 and 5 oxidation states Both are white solids at room temperature Tetraphosphorus hexaoxide P405 is formed by heating white p phosphorus in an oxygen de cient environment The structure of P406 consists of a tetrahedron of phosphorus atoms with bridging oxygen atoms between the P atoms rather than P P bonds A P45 3029 gt P4065 O P O 1518 Tetraphosphorus decaoxide P4010 is formed by heating white 0 phosphorus in an excess of oxygen The structure of P4010 is based on the P406 structure with terminal 0 atoms bonded to each P atom A P4 5 5 02 9 P4010S O O l 0 l o Tetraphosphorus decaoxide is a potent dehydrating agent and P I 7O forms phosphoric acid as it absorbs water 0 O P O P4010 s 6 H20 0 9 4 H3PO4 aq i It is capable of dehydrating nitric acid to N205 Halides of Phosphorus Phosphorus forms two series of halides PX3 and PXS representing the 3 and 5 oxidation states respectively Trihalides other than PF3 are formed by the direct reaction between the halogen and an excess of phosphorus PF3 is formed by the uorination of PC13 P4S 6029 gt 4PC3 Pentahalides other than PF5 are formed by the reaction of phosphorus and an excess of the halogen PF5 is formed by the reaction of PC15 with CaF2 at 3004000C P4 5 10 a2 g 4PCI5s Unlike NCIS which is hydrolyzed to NH3 and HClO PCl3 is hydrolyzed in a multistep process to phosphonic acid commonly referred to as phosphorous acid PC13 0 3 H20 0 a H3PO3 a 3 HCl g PCl5 undergoes hydrolysis to phosphoric acid in a series of steps The rst step yields phosphoryl chloride alm phosphorus oxychloride POCl3 POCIS subsequently undegoes further hydrolysis to the acid PC15 s H20 0 a POC13 a 2 HCl g 130013 03 H20 H3PO40 3HC1 g 1519 PCl3 has atrigonal pyramidal geometry due to the lone pair on P 39 PCl5 has a trigonal bipyramidal geometry in the liquid and vapor phase Cl However in the solid phase it exists as an ionic compound POLY PC1639 where the cation is tetrahedral and the anion is octahedral in geometry CI CI Cl 39 C C39 quotquotll PI J CI P a 39I39 CI P CI CI CI 0 I 539 CI CI Phosphorus Oxychloride Phosphorus oxychloride is a dense toxic liquid which reacts with trace moisture in the air and is the stalting material for a great deal of phosphorus chemistry It is produced on an industrial scale by the catalytic oxidation of PC13 2 13013 a 02 g a 2 130013 0 although it can also be prepared by the reaction of PC5 with a stoichiometric amount of water 13015 s H20 130013 a 2HC1 g 1520 Phosphorus Oxoacids Phosphorus forms a series of oxoacids with interesting properties phosphoric acid H3PO4 phosphonic acid commonly referred to as phosphorous acid H3PO3 and phosphinic acid commonly referred to as hypophosphorous acid H3P02 In an oxyacid a hydrogen atom is ionizable if it is bonded to an oxygen atom In most series of oxoacids terminal oygen atoms are typically lost as the oxidation state of the central atom decreases For example sulfuric acid and sulfurous acid whose structures are shown are both diprotic T acids quot Squot 5quot H O I quot39o H ol quot o O O H H However as we proceed from phosphoric acid to phosphorous acid to hypophosphorous acid bridging O atoms are lost leaVing an H atom bonded directly to P As a result those H atoms are not ionizable and while phosphoric acid is a triprotic acid phosphorous acid is diprotic and hypophosphorous acid is monoprotic o o l u H oo H H Ol H o Ho Ho H Phosphoric Acid Pure orthophosphoric acid is a colorless syrupy liquid and a concentrated aqueous solution of the acid is 85 by mass H3PO4 with a molar concentration od about 147 M Unlike nitric acid it is essentially a nonoxidizing weak triprotic acid H3P04 aq H20 0 e H2P04 aq H30 aq H2130 aq H200 e HP042 aq H30 aq HP042 211 211 H20 0 P04 211 t H30 211 1521 The pure acid is obtained by the thermal process which involves buming white phosphorus in excess oxygen to produce P4010 and then treating the oxide with water P4 5 5 02 g P4010 S P4010 S 6 H20 9 a 4 H3P04 aq It can also be prepared by treating calcium phosphate with sulfuric acid in a process known as the wet process 021303042 s 3 HZSO4aq 3 CaSO4s 2 H3PO4aq Heating phosphoric acid leads to the loss of water and the O 0 formation of a series of condensed phosphoric acids The rst of these is pyrophosphoric acid H4P207 Hoiioiiol HO HO 2 H3P04 I gt H4P207 I H20 I Pyr Ph SP quoti id Further condensation leads to triphosphoric acid 0 lt1quot lt1quot H5P3010 P P oiiOloloH Ho HO 9 3H4P2070 i 2H5P3010I H200 Triphosphoric acid Metaphosphoric acid is polymeric anPo4I i FPOsn nHzoa ol 0l 0 O metaphosphor ic acid 1522 Phosphates The phosphate ion PO4339 is very basic and subject to hydrolysis in aqueous solution Hydrolysis leads to the formation of hydrogen phosphate dihydrogen phosphate or even phosphoric acid depending on pH 1304 aq H20 0 e HPOf aq 0H aq HPO aq H20 0 e H2130 aq 0H aq HzPor aq H20 0 e H3P04aq 0H aq With the high charge of the phosphate ion most phosphates have relatively high lattice enthalpies and are typically insoluble Only those of the allmli metals and ammonium ion are soluble Sodium phosphate Na3PO4 is very basic and is used as an effective degreaser and industrial cleaner known as TSP for trisodiurn phosphate Solid hydrogen and dihydrogen phosphates are only known for monopositive cations and the larger dipositive cations Recall that large anion are only stabilized by cations of low charge density The Remaining Elements Hydrides The stability of the hydrides decreases going down the family This is primarily due to the decreasing XeH bond strength as X becomes larger and orbital overlap becomes less effective NH3 gt PH3 gt AsHs gt SbHs gt BiH3 J Tba39mally unstable The basicity decreases in the same order l 523 Halides Arsenic trihalides may be hydrolyzed to a1senous acid like the phosphorus ttihalides AsClS 0 3 H20 0 a H3As03 a 3 HCl g Antimony and bismuth ttihalides yield oxychlorides in reversible reactions BiClS 0 H20 0 BiOCl s 2 HCl aq Pentahalides especially the uorides of P As and Sb are very good Lewis acids but the ttihalides are not Lewis acids Oxides The stability of higher oxidation state decreases with increasing atomic number For example bismuth V oxide has never been isolated as a pure substance In a given oxidation state the metallic character of the elements and therefore the basicity of the oxides increases with increasing atomic number increasing basici ry gt P406 lt AS406 lt Sb406 lt Bi203 l acidic ampho rer ic basic
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