TRNG I HC KHOA HC HU KHOA HA

TS. TRN NGC TUYN

BI GING

HO HC V C(INORGANIC CHEMISTRY)

Hu 2008

Chng 1. HIDRO - OXI - NC1.1. HIDRO 1.1.1. c im chung Nguyn t hidro c cu trc n gin nht (1s1), gm mt electron v mt ht nhn mang in tch +1 gi l proton. Hidro c 3 ng v: ng v Hm lng (%)1 1

H (H)

2 1

H (D)

3 1

H (T)

99.984

0.016

0.0001

H v D l 2 ng v bn, T l ng v phng x. Do c cu trc c bit nn H c 3 kh nng: + Mt electron ha tr to thnh ion H+: H - e H+ H = 313,5 kcal/ntg Kh nng ny th H ging kim loi kim nhng nng lng ion ha ca H ln hn nhiu so vi kim loi kim. Proton c kch thc ( 1,5.10-13cm) b hn nhiu so vi nguyn t (10-8cm) v mang in tch nn mt in tch ln, c kh nng lm nhiu lon m my electron ca cc nguyn t xung quanh. V th, proton khng th tn ti mt mnh m lun kt hp vi phn t hay nguyn t khc. Chng hn: H+ + H2O H3O+ + Kt hp vi electron to thnh ion H-: H + e HH = -16 kcal/ntg Ion H- c cu trc electron ca He, v th H- t do c kh nng tn ti trong cc hidrua mui nh KH, CaH2. V kh nng ny, H ging nh halogen, nhng i lc i vi electron ch bng 1/5 i lc electron ca halogen. + To nn cp electron chung cho lin kt cng ha tr: Lin kt ny c th khng phn cc nh trong phn t H2, hoc c cc nh trong phn t HCl. Do c cc kh nng nh trn nn H c mt v tr c bit trong Bng HTTH, n va ging, va khc vi kim loi kim v halogen. Nu phi xp H vo mt trong 2 nhm th xp vo nhm halogen hp l hn. Do bn cht ca proton v do khng c lp electron no chn in tch ht nhn, H c nhng c im m nhng nguyn t khc khng c c nh to lin kt hidro v cc hp cht khng hp thc vi kim loi. 1.1.2. Tnh cht l hc - Dng tn ti trng thi t do l H2. Nng lng lin kt H - H l 103Kcal/ptg, di lin kt l 0,74 . Phn t H2 c bn ln, kh b phn cc ha, nhit nng chy v nhit si rt thp. - Kh H2 khng mu, khng mi v khng v, nh nht trong tt cc cc kh nn n c tc khuch tn ln (3,5 ln so vi khng kh). Do H2 c dn nhit ln, dng lm ngui rt tt. Mt khc v rt nh nn trc y H2 thng c dng bm vo cc kh cu.1

1.1.3. Tnh cht ha hc - Phn t H2 c bn ln nn kh phn hy thnh nguyn t. N ch phn hy r rt 2000C: H2 2H H = 103 kcal/ptg. V th nhit thng H2 rt km hot ng. Ch khi un nng n mi kt hp vi nhiu nguyn t. - H2 c th kt hp trc tip vi kim loi kim v kim th to nn hidrua kim loi: H2 + Na NaH H2 + Ca CaH2 - H2 c th kt hp vi cc nguyn t phi kim nh: O, S, N... H 2 + O 2 H 2O H = - 63kcal/mol - H2 c th kh cc oxit kim loi nh: CuO, Fe2O3, HgO, PbO... H2 + CuO Cu + H2O H2 + Fe3O4 Fe + H2O - Khi c mt Pt lm xc tc, H2 c th kh cc hp cht hu c khng no thnh hp cht no, andehit thnh ru... - Hidro mi sinh c kh nng kh rt mnh. nhit thng hidro nguyn t c th kt hp vi O, S, P, As, kh c nhiu oxit kim loi, y c mt s kim loi nh Cu, Ag, Pb ra khi dung dch mui ca chng, tham gia vo nhng phn ng m iu kin H2 khng th phn ng c. 1.1.4. Trng thi thin nhin v phng php iu ch 1.1.4.1. iu ch a. Trong cng nghip Hidro c iu ch theo cc phng php khc nhau: - Phng php i t than: Ngi ta cho hi nc i qua than cc t nng n 1000oC v thu c mt hn hp 2 kh CO v H2 gi l kh than: C + H2O CO + H21000o C

H = 130kJ/mol

- Phng php i t kh thin nhin: Cho hn hp kh thin nhin v hi nc c t nng n 1000oC i qua cht xc tc Ni: CH4 + H2O CO + 3H21000o C , Ni

H = 209kJ/mol

Kh thin nhin cng c th c t chy khng hon ton trong oxi hay khng kh to thnh kh than: 2CH4 + O2 2CO + 4H2 H = - 71kJ/mol

2

- Phng php in phn: Phng php in phn nc cho hidro tinh khit. Trong cng nghip ngi ta in phn dung dch NaOH 25%, H2 bay ra cc m v O2 bay ra cc dng. Dteri c dng lm cht lm chm ntron trong l phn ng ht nhn. Trong ho hc teri c dng cho vic nghin cu c ch ca cc phn ng. iu ch teri ngi ta in phn nc nng. b. Trong PTN Trong PTN hidro c iu ch bng cch cho Zn tc dng vi axit H2SO4 long hoc axit HCl trong bnh kp: Zn + H2SO4 ZnSO4 + H2 Trong trng hp dng Zn tinh khit, phn ng xy ra rt chm, cn phi cho thm vo mt lng mui ng phn ng xy ra nhanh hn. 1.1.4. ng dng Hidro c s dng rng ri trong nhiu ngnh cng nghip: - Nguyn liu cho cc ngnh: cng nghip ho hc (tng hp NH3, HCl), cng nghip thc phm (hidro ho du m, sn xut margarin...), cng nghip luyn kim (hidro dng lm cht kh kh cc qung). - Hidro lng c s dng trong k ngh tn la, hidro nguyn t c s dng ch to cc hp kim siu cng. - Cc ng v nng ca hidro (D2, T2) ng vai tr quan trng trong vic iu ho cc phn ng ht nhn. 1.2. HIDRUA Hidrua l hp cht ca hidro vi mt nguyn t khc. Da vo bn cht ca lin kt ho hc trong hp cht, ngi ta phn chia cc hidrua ra lm 3 loi: hidrua ion, hidrua cng ho tr v hidrua kiu kim loiLi Na K Rb Cs Ca Sr Ba Sc Y La Ti Zr Hf V Ta Cr W Mn Re Fe Os Co Rh Ir Ni Pd Pt Cu Ag Zn Cd Ga In Tl Nb Mo Tc Ru C Si Ge Sn Pb N P As Sb Bi O S Se Te Po F Cl Br I At

Au Hg

Hidrua ion

Hidrua kiu kim loi

Hidrua cng ha tr

1.2.1. Hidrua ion Hidrua ion l cc cht dng tinh th khng mu, ging vi mui nn c gi l hidrua mui. Hidro c i lc electron rt b v xu hng to thnh ion m ca n rt yu so vi cc halogen l nguyn t m in hn.1/2H2(k) H(k) H(k) + 1e H-(k) H = 218 kJ/mol H = -66 kJ/mol 1/2Br2(k) Br(k) Br(k) + 1e Br-(k) H = 113 kJ/mol H = -326kJ/mol

1/2H2(k) + 1e H-(k) H = 152 kJ/mol 3

1/2Br2(k)+1e Br-(k) H = 213 kJ/mol

Do tnh thu nhit ca ion H- cho nn ch nhng kim loi hot ng mnh nh kim loi kim, kim loi kim th mi c th to nn cc hidrua ion. 1.2.1.1. Tnh cht vt l Hidrua ion c cc c tnh sau: - C nhit nng chy cao, iu kin thng chng l cc cht kt tinh mu trng. - Khi nng chy c dn in kh cao - Khi in phn nng chy c kh hidro thot ra anot. 1.2.1.2. Tnh cht ho hc Nhit to thnh ca cc hidrua ion khng cao, do chng km bn, nhit cao chng b phn hy cho cc n cht. Nhit to thnh ca cc hidrua ion Cht LiH NaH KH RbH Nhit to thnh (Kcal/mol) 21.7 14.4 14.2 20.3 Cht CsH CaH2 SrH2 BaH2 2NaH 2Na + H2 Trong kh quyn hidro, chng bn hn v c th nng chy, phn ly thnh ion: MH M+ + H- Anion H- c tnh baz rt mnh, nn ch tn ti trong mng tinh th. Khi tip xc vi cc cht c kh nng cho H+ n phn ng rt mnh lit. Do cc hidrua ion b phn hu hon ton trong nc cho mi trng kim mnh: NaH + H2O NaOH + H2 - Cc hidrua ion c tnh baz nn chng phn ng vi cc hidrua axit (trong dung mi khng nc) to thnh cc phc hidrua: LiH + AlH3 Li[AlH4] LiH + BH3 Li[BH4] Thc t l phn ng: H- + BH3 [BH4]- H- rt d mt electron, cc hidrua ion l cc cht kh rt mnh, l mt trong cc cht kh mnh nht c bit: H2 + 2e 2H1.2.2. Cc hidrua cng ho tr Xp vo loi ny l cc hp cht gia hidro vi cc nguyn t km m in hn n nhng khng c kh nng to thnh hidrua ion. Lin kt trong loi hidrua ny c bn cht cng ho tr hoc ion cng ho tr. Tu thuc vo cu trc electron ca4

Nhit to thnh (Kcal/mol) 19.9 46.6 42.2 41.0

- LiH v NaH b phn hu nhit khong 350 600C:

Eo = -2,25V

nguyn t dng in m cc cht c cu trc phn t v cu to trng thi rn khng ging nhau. 1.2.2.1. Cc hidrua cng ho tr d bay hi c to thnh gia hidro vi cc kim loi hoc mt s phi kim c s electron ho tr bng hoc ln hn s phi tr ca nguyn t . V d: Hidrua ca cc nguyn t m in km nhm IVA v VA ca bng h thng tun hon: SiH4, GeH4, SnH4, AsH3, PH3, SbH3... trng thi rn chng c mng tinh th phn t, do nhit nng chy v nhit si thp. Cc hidrua loi ny c bn cht axit. Do nguyn t H c s oxi ho (-1) nn n cng c cc tnh cht ging hidrua ion: - Khng bn, nhiu hidrua b phn hu ngay khi va to thnh: 2SbH3 2Sb + 3H2 - B thu phn mnh, gii phng H2: SiH4 + 4H2O H4SiO4 + 4 H2 - C tnh kh mnh, nhiu cht t bc chy khi tip xc vi oxi ca khng kh: 2PH3 + 4O2 2H3PO4 1.2.2.2. Cc hidrua cng ho tr kh bay hi c to thnh bi cc kim loi hoc phi kim c s electron ho tr nh hn s obitan ho tr c kh nng tham gia lin kt (thng l cc nguyn t thuc nhm IIA hoc IIIA). V d: BeH2, B2H6, AlH3, ZnH2, InH3...Cc hidrua c tnh cht trung gian gia hidrua ion v hidrua cng ho tr d bay hi. Chng thng c tnh cht lng tnh. Trong dung mi khng nc n phn ng c vi cc hidrua ion v hidrua cng ho tr. V d: BeH2 + 2NaH Na2[ BeH4] BeH2 + 2BH3 Be [BH4]2 Nhn chung cc hidrua cng ho tr km bn hn nhiu so vi hidrua ion v thng c iu ch bng phng php gin tip. 1.2.3. Cc hidrua kiu kim loi Cc nguyn t chuyn tip cng to thnh hp cht bc hai vi hidro v cng thng gi l hidrua. Mc d c gi l hidrua nhng y l cc hp cht c lin kt kim loi, c thnh phn khng hp thc gn vi cc cng thc l tng MH, MH2, MH3. Thng cc hp cht ny l cc cht rn c mu xm dn in v dn nhit tt. Hin nay c 2 thuyt gii thch tnh dn in kim loi ca cc hp cht ny. Thuyt th nht cho rng H xm nhp vo mng tinh th kim loi di dng ion H+ v nhng electron ho tr cho vng dn ca kim loi. Thuyt th hai cho rng H nhn electron ca vng dn ca kim loi v tn ti trong mng tinh th di dng ion H-. Do c tnh kh mnh, cc hidrua ion, hidrua phc, hidrua kim loi v hidrua cng ho tr khng bay hi thng c s dng rng ri lm cht kh trong nhiu qu trnh tng hp khc nhau. c bit cc hidrua kiu kim loi do c tnh gin, d nghin thnh bt mn, thng c s dng iu ch kim loi dng bt.

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1.3. OXI 1.3.1. Nhn xt chung - Nguyn t O c cu hnh electron: 1s2 2s2 2p4. L nguyn t u tin ca nhm VIA, thuc chu k 2 v l nguyn t c s electron ho tr ln hn s obitan ho tr nn oxi c nhiu c tnh khc hn cc nguyn t cng phn nhm. Tnh cht ca nguyn t Bn knh CHT (nm) 0.066 NL ion ha th nht I1 (eV) 13.61 m in 3.5

- Do c bn knh nh, c 2 electron c thn v l nguyn t c m in ln (ch km F), s oxi ho c trng nht ca oxi l -2, s oxi ho +2 ch gp trong cc hp cht vi F. - Trong cc hp cht c s to thnh lin kt gia cc nguyn t O-O n c th c s oxi ho +1. - Ho tr v s phi tr cc i ca oxi trong cc hp cht cng ho tr l 4, nhng mun t n ho tr v s phi tr ny, nguyn t oxi phi s dng cp electron cha lin kt ca mnh to lin kt cho nhn vi nguyn t ca nguyn t khc. Chnh v vy, ho tr v s phi tr thng gp ca oxi l 2. 1.3.2. Trng thi t nhin Oxi l nguyn t ph bin nht. N chim 47% khi lng v 55% NT ca cc nguyn t to thnh v tri t. Oxi c 3 dng ng v bn 16O (99,759%), 17O (0,03%) v 18O (0,204%). Ngoi ra cn c cc ng v phng x nhn to 14O, 15O c chu k bn phn hu vi chc giy. Trong t nhin, oxi tn ti di dng t do hoc dng hp cht ca cc nguyn t. Do c hm lng rt ln, li l nguyn t c hot tnh ho hc rt cao nn oxi quyt nh dng tn ti ca hu ht cc nguyn t trong t nhin. 1.3.3. n cht Oxi tn ti 2 dng th hnh: oxi (O2) v ozon (O3), dng bn nht l O2. 1.3.3.1. Oxi a. Cu to phn t - Tnh cht vt l Oxi tn ti dng phn t 2 nguyn t (O2). Theo phng php MO, cu hnh electron ca phn t l: (S)2 (S*)2 (Z)2 (X, Y)4 (X*, Y*)2 ng vi bi lin kt l 2, c th biu din cu trc phn t nh sau: :O - O: hoc :O - O: Ngha l trong phn t c mt lin kt 2 electron v 2 lin kt c bit, mi lin kt gm 3 electron. Cc cng thc ny ph hp vi tnh cht thun t ca oxi, cn cng thc Lewis :O::O: khng ph hp vi iu ny. Khong cch gia cc oxi trong phn t oxi l 0,1207nm, ngn hn so vi lin kt n O-O (0,148nm) do phn t O2 rt bn vng v c phn cc nh: O2 2O Hpl =118 kcal/mol.6

- Oxi ch phn ly thnh nguyn t nhit ln hn 2000C hoc khi chiu tia t ngoi. - Oxi c nhit nng chy v nhit si thp (tonc= - 218,9oC, ts = -183C), trng thi rn c mng tinh th phn t. nhit bnh thng, oxi l mt cht kh khng mu, khng mi v, t tan trong nc ( 90C, 100 th tch nc ho tan c 5 th tch oxi). b. Tnh cht ho hc Oxi l mt trong nhng phi kim hot ng mnh nht. Kh nng phn ng ca oxi tng rt mnh khi c xc tc v nhit cao: - Ngay nhit thng, oxi c kh nng phn ng vi nhiu n cht v hp cht gy ra cc hin tng thng c gi l s oxi ho hoc s r. Oxi tc dng trc tip vi tt c cc kim loi to thnh oxit, peoxit tr Au, Pt (i vi Ag th Ag2O ch to thnh khong 200 - 250C, nu nhit cao hn th Ag2O li b phn hu). 4Na + O2 2Na2O 2Na + O2 Na2O2 - i vi cc phi kim, tr halogen, kh tr, oxi tc dng trc tip nhng thng thng cn c nhit : C + O2 CO22000 C N2 + O2 2NO o

- Phn ng ca oxi vi nhiu hp cht, n cht, nhiu phn ng to ra nhit lng ln v pht sng, thng c gi l s chy. c. iu ch - Trong cng nghip, ch yu oxi c iu ch bng phng php ho lng khng kh, sau chng ct phn on khng kh lng. i khi ngi ta cng iu ch bng cch in phn nc. - Trong PTN: thng s dng oxi c nn trong cc bnh thp. Khi mun iu ch lng nh oxi, c th phn hu nhit cc hp cht giu oxi nh KMnO4, KClO3, HgO: 2HgO 2Hg + O2 2KClO3 2KCl + 3O2 2KMnO4 K2MnO4 + MnO2 + O2 d. ng dng ng dng ch yu ca oxi l to nhit cao cn thit cho qu trnh luyn kim, nu chy Pt, thch anh. Oxi lng c dng cho k ngh tn la. Kh oxi cng c dng trong y hc. 1.3.3.2. Ozon a. Cu to phn t Tnh cht vt l Phn t ozon O3 trc y mt thi gian di c coi c cu to vng kn. Nhng cu to khng ph hp vi l thuyt hin i. V mt nhit ng hc, phn t c cu to nh vy khng th c c. V nng lng phn hy ca phn t O2 ch7MnO 2 , t o

khong 118kcal v nng lng lin kt cng ha tr -O-O- l khong 30kcal nn entanpy ca phn ng 3O2 2O3 c tnh theo chu trnh sau:O

3O2

3 x 118

6O6 x 30

H

O

O

2O3

phi l: H = 354 - 180 = 174kcal. Nhng gi tr thc nghim xc nh c l 68 kcal. Mt khc momen lng cc phn t xc nh c cng khng ph hp vi cu to i xng . Phn t ozon c cu to dng gc, mi phn t O3 c 2 lin kt v mt lin kt khng nh ch:O

O

O

iu kin thng ozon l mt cht kh c mu xanh da tri v c mi c bit. Phn t O3 c khi lng tng i ln, c cc v d b phn cc ho nn ozon c nhit nng chy v nhit si cao hn oxi (ts = -111,9oC, tnc = - 192,7C). Ozon lng c mu tm v t khi l 1,71. Ozon rn c mu tm en. L phn t c cc (momen lng cc = 0,52D), ozon tan trong nc nhiu hn oxi 15 ln. b. Tnh cht ho hc - Ozon km bn d b phn hu: 2O3 3O2 H = - 285kJ Do d phn hu cho oxi nguyn t nn ozon hot ng hn oxi nhiu. Trong cc phn ng n s gii phng ra O2 - iu kin thng, ozon c th oxi ho c nhiu n cht v hp cht c hot tnh rt km bn l cc cht m O2 ch tc dng nhit cao: 2Ag + O3 Ag2O + O2 2KI + O3 + H2O 2KOH + I2 + O2 PbS + 4 O3 PbSO4 + 4 O2 Nhiu cht hu c phn ng mnh lit vi ozon (bng, este, du thng... bc chy khi tip xc vi ozon). C th thy r tnh oxi ho ca ozon khi so snh th oxi ho - kh ca n vi oxi: O3(k) + H2O + 2e O2(k) + 2OH-(dd) O2(k) + 2H2O + 4e 4OH-(dd) O3(k) + 2H+ + 2e O2(k) + H2O O2(k) + 4H+ + 4e 2 H2O8

o = 1,24V o = 0,4V o = 2,07V o = 1,229V

- Ozon tc dng vi cc kim loi km to ra ozonua: K + O3 KO3 c. iu ch - Trong t nhin, ozon c hnh thnh tng kh quyn cao (10 30km) nh tc dng ca tia t ngoi ln oxi. Phn ng xy ra theo s chui: O2 + h O2* O2* + O2 O3 + O O + O 2 O3 Phn ng ny c ngha rt ln v phn ln nhng tia t ngoi c hi cho s sng u b gi li. - iu ch ozon trong k thut, thng dng phng php phng in m qua kh quyn oxi c p sut thp. - Trong PTN, iu ch mt lng nh ozon ta c th s dng phn ng ca (NH4)2S2O8 vi HNO3 hoc H2SO4 m c. d. ng dng Ozon c s dng trong thc t do tnh oxi ho mnh ca n, n thng c dng st trng nc ung v khng kh hoc trong tng hp ho hc khc nhau. 1.3.4. Oxit ca cc nguyn t Oxit l hp cht ca oxi vi mt nguyn t khc. Oxit ca cc nguyn t c bn cht rt khc nhau. Kiu lin kt ho hc trong cc oxit bin i t thun tu ion n thun tu cng ho tr. S to thnh ion O2- t O2 tiu tn mt nng lng kh ln: 1/2O2(k) O(k) O + 2e O2-(k) 1/2O2(k) + 2e O2-(k) H = 59kcal/mol H = 157kcal/mol H = 216kcal/mol

Mun to thnh oxi ion cn tiu tn mt nng lng ln lm cho nguyn t kim loi bay hi v ion ho, nhng mt khc nh nng lng mng li ca oxit cha ion O2- tng i b (1,4 ) l rt cao cho nn nhiu oxit thun tu ion v rt bn. Da vo tnh cht ho hc ngi ta phn chia oxit ca cc nguyn t ra lm oxit baz, oxit axit, oxit lng tnh, oxit trung tnh. 1.3.4.1. Oxit baz - l cc oxit ca kim loi nh kim loi kim, kim th. Thng l cc cht rn c nhit nng chy cao, nhiu cht tan trong nc cho mi trng kim: Na2O + H2O 2NaOH BaO + H2O Ba(OH)2 - Mt s khng tan trong nc nhng tan c trong cc axit MgO + 2HCl MgCl2 + H2O9

1.3.4.2. Oxit axit - L cc oxit ca cc phi kim v cc phi kim s oxi ho cao, lin kt mang tnh cht cng ho tr. trng thi rn, chng thng c mng tinh th phn t hoc cu trc phn lp, mch, nn nhit nng chy khng cao. - Oxit axit gi l anhidrit l oxit tan c trong nc to thnh axit tng ng.V d: SO3, N2O5, Cl2O7... SO3 + H2O H2SO4 N2O5 + H2O 2HNO3 - Nhng oxit axit khng tan trong nc c th tan trong dung dch kim hoc trong kim nng chy: SiO2 + 2NaOH (r) Na2SiO3 + H2O Sb2O5 + 2NaOH + 5H2O 2Na[Sb(OH)6] 1.3.4.3. Oxit lng tnh - L cc oxit c tnh cht trung gian gia oxit axit v oxit baz. V d: Al2O3, Cr2O3, ZnO... thng l cc cht rn, khng tan c trong nc, nhng tan c trong c axit v kim: ZnO (r) + 2H+(dd) Zn2+(dd) + H2O ZnO (r) + 2OH-(dd) + H2O Zn(OH)42- Cch phn chia ra oxit baz, oxit axit v oxit lng tnh l da vo tnh axit - baz ca oxit trong dung dch nc, cch phn chia nh vy cng ph hp vi cch phn chia oxit da vo kiu lin kt ho hc. Tnh axit tng, tnh cng ha tr tng Li2O Na2O K2O Rb2O Cs2O BeO MgO CaO SrO BaO Oxit baz B 2O 3 Al2O3 Ga2O3 In2O3 Tl2O3 CO2 SiO2 GeO2 SnO2 PbO2 Oxit lng tnh Tnh baz tng, tnh ion tng Trong mt chu k, t tri sang phi tnh axit tng ln cng vi tnh cng ho tr ca lin kt trong phn t oxit v ngc li tnh baz gim xung cng vi tnh ion ca lin kt. 1.3.4.4. Oxit tr - Ngoi cc oxit thuc ba loi trn cn tn ti mt s oxit c nhng tnh cht kh c bit, chng kh tr v phng din ho hc, khng tan trong nc v khng tan c trong axit v baz. V d: N2O, CO, MnO2, PbO2. N2O5 P4O10 As2O3 Sb2O5 Bi2O5 Oxt axit SO3 SeO3 TeO3 F 2O Cl2O7 Br2O I2O5

10

- Nu cc oxit ny phn ng vi axit hoc baz th phn ng khng phi l phn ng axit - baz. V d: MnO2 khng tan trong HNO3, H2SO4 nhng phn ng vi axit c. MnO2 + 4HCl MnCl2 + Cl2 + 2H2O 1.3.5. Peoxit L cc oxit c cha ion O22-. Ion O22- c cu to [:O-O:]2-, cc kim loi kim, kim th to nn peoxit, y l cc peoxit ion.V d: Na2O2, BaO2 cc oxit ny khi tc dng vi nc gii phng H2O2: Na2O2 + 2H2O 2NaOH + H2O2 Vy c th coi peoxit l mui ca H2O2, cng nh H2O2 peoxit l cht oxi ho mnh nhng vi cht oxi ho mnh hn, n th hin tnh kh. 1.3.6. Supeoxit L oxit c cha ion O2- trong mng li tinh th. Cc kim loi kim cho supeoxit, v d: KO2, RbO2. Khc vi peoxit, khi tc dng vi nc ngoi H2O2, supeoxit cn gii phng O2, v vy supeoxit l cht oxit mnh: 4KO2 + 6H2O 4KOH + 4H2O2 + O2 1.3.7. Ozonit L oxit c cha ion O3- trong mng li tinh th ion ny c cu to tng t ozon. Ngi ta bit c ozonit ca kim loi kim nh KO3, RbO3. Khi tc dng vi nc chng khng gii phng H2O2 m gii phng oxi vi lng nhiu hn: 4KO3 + 2H2O 4KOH + 5O2 1.4. NC Hidro v oxi to nn cc hp cht nh nc (H2O), hidropeoxit (H2O2). Nc l hp cht quan trng nht. Do hm lng ln v do c nhng tnh cht l ho hc c bit, nc ng vai tr v cng quan trng trong cc qu trnh sng, nc l dung mi quan trng nht tin hnh cc phn ng ho hc. 1.4.1. Cu to Cc phn t nc c cu to dng gc:H O105oA 94 0,9o

H

- Gia cc phn t nc hnh thnh cc lin kt hidro kh bn vng c trng thi lng v trng thi rn. Khi trng thi rn, nc c mng tinh th phn t vi lc gi cc phn t cc nt mng l lin kt hidro. Trong nc mi phn t nc c lin kt vi 4 phn t nc khc nh lin kt hidro. Cu trc ny rt rng nn nc c t khi nh. trng thi lng do lin kt hidro nn cc phn t nc b t hp 2, 3 hoc 4 phn t. Chnh do s tn ti ca lin kt hidro nn nc c nhng tnh cht l ho hc khc nhiu so vi cc hp cht cng kiu. - Do c cu to khng i xng nn H2O l phn t c cc, di lng cc l 0,39 v cc tnh ln ( = 1,84D).11

- Phn t H2O rt bn i vi nhit, bt u phn hu 1000C v n 2000C th phn hu khong 2%: 2 H2O 2H2 + O2 1.4.2. Tnh cht vt l Nc l mt cht lng trong sut, khng mu, khng mi v khng v. Lp nc dy c mu xanh lam nht. Nc c nhit nng chy v nhit si cao hn hn hn cc hp cht cng kiu: ts = 100C, tnc = 0C. T khi ca nc cng thay i mt cch bt thng: Nhit (C) d (g/cm3) 0 0,9999866P

H = 135 Kcal/mol

4 1

10 0,999727

15 0,999127

20 0,99823

L K R to

Gin trng thi ca nc nhit 0,01C v p sut hi 0,006 atm, nc c th tn ti ng thi 3 trng thi: nc , nc lng v hi nc. Nhit gi l im ba ca nc trn gin trng thi ca nc. Nc c nhit dung ring ln nht so vi mi cht lng v rn. Lng nhit cn thit un nng 1ml nc t 14,5C ln 15,5C c dng lm n v nhit gi l calo. Nh c nhit dung ln, nc c vai tr rt quan trng trong vic iu ho kh hu ca qu t. 1.4.3. Tnh cht ho hc Nc c kh nng phn ng rt mnh. N c th phn ng vi rt nhiu n cht v hp cht. Khi phn ng, nc th hin cc khuynh hng ch yu sau y: - Tnh cht lng tnh theo quan im ca Bronsted: H2O + H2O H3O+ + OHChnh tnh cht ny ca nc dn n s thu phn ca cc mui trong dung dch nc cng nh s xut hin tnh cht axit hoc baz ca mt s cht khi ho tan vo nc. - Tnh oxi ho - kh: H2O c th b kh to thnh H2, trong phn ng ny, chnh H+ ca nc b kh: 2 H+ + 2e H2 2Na + 2H2O 2NaOH + H2 N cng c th b oxi ho gii phng O2:12

2H2O - 4e O2 + 4H+ 2H2O + 2F2 O2 + 4HF - Th oxi ho - kh ca 2 qu trnh trn ph thuc vo pH v p sut ca kh H2 v O2 thot ra. Theo phng trnh Nernst: 1 = - 0,02951lg [PH2] - 0,059pH 2 = 1,23 + 0,0147lg [PO2] - 0,059pH C tnh kh v tnh oxi ho ca nc khi mi trng trung tnh khng cao cho nn ch c cc cht kh rt mnh mi y H2 ra khi nc (kim loi kim, kim th) v nhng cht oxi ho rt mnh (F2, O3, XeF6, Co3+) mi oxi ha c nc. - Nc c th phn ng nh mt baz Lewis (do cc cp electron khng lin kt trn nguyn t O) nn n c kh nng ng vai tr ca phi t to phc aqu vi nhiu ion kim loi. V d: [ Cr(H2O)6]3+, [Co(H2O)6]2+, [Fe(H2O)6]2+... - Do c s hidrat ho cation v anion dn n s hnh thnh cc hp cht trong thnh phn ca chng c cha mt s phn t nc c gi l cc hp cht hidrat. C nhng hidrat km bn ch tn ti trong dung dch nc, nhng cng c nhiu hidrat bn vng, c th tch khi dung dch dng tinh th c gi l cc tinh th hidrat, v d: CuSO4.5H2O. Nc c trong mng tinh th ca cc hidrat c gi l nc kt tinh. Nhiu mui kim loi to c nhiu tinh th hidrat vi s phn t nc kt tinh khc nhau. - Thng cc mui hidrat c tan trong nc ln hn so vi cc mui khan tng ng v chng c mng tinh th ion hoc c phn cc ln hn. Trn b mt ca cc tinh th hidrat lun tn ti mt p sut hi nc bo ho. Tu thuc vo bn cht ca cht v nhit , p sut ny s thay i. Nu p sut hi nc bo ho ca tinh th nh hn p sut hi nc trong kh quyn, cc tinh th hidrat ny thng d b chy ra khi trong khng kh. Nu p sut hi nc trong kh quyn thp hn th cc tinh th hidrat d mt i mt phn nc kt tinh ca mnh khi trong khng kh. Hin tng c gi l s ln hoa. 1.5. CC HP CHT PEROXIT - S kt hp thm 1e vo phn t O2 s dn n s hnh thnh O2- (supeoxit) O2 + 1e O2O2- + 1e O22H = 20,3kcal/mol. H =130,3kcal/mol - Khi kt hp thm 2e dn n s hnh thnh anion O22- (peoxit) Qu trnh nhn thm electron vo phn t O2 l qu trnh in thm electron vo cc obitan phn lin kt nn s dn n s lm gim bn lin kt gia cc nguyn t O trong ion O2+ bi lin kt NLLK (kJ/mol) 2,5 641 O2 2 493 O21,5 O221 210

13

V vy cc peoxit thng km bn hn so vi cc oxit tng ng. Tuy nhin, bn ca cc peoxit v cc supeoxit ph thuc nhiu vo cc nguyn t dng in. Cation c kch thc cng nh in tch cng ln, peoxit ca n cng km bn. 1.5.1. Peoxit n gin - Ngi ta tng hp c peoxit ca nhiu nguyn t nhng ch c peoxit ca kim loi kim v H2O2 l c ng dng thc t. Peoxit ca cc kim loi kim l cht rn bn iu kin thng, chng c iu ch bng phn ng ca oxi trc tip vi kim loi hay oxit kim loi. - Peoxit kim loi kim, kim th c tnh cht baz, chng b thu phn bi nc hoc phn ng vi cc axit gii phng ra H2O2: Na2O2 + H2O NaOH + H2O2 BaO2 + H2SO4 BaSO4 + H2O2 y chnh l phn ng dng phn bit cc peoxit vi oxit ca cc kim loi s oxi ho cao (v d: MnO2, PbO2, SnO2) - Cc peoxit th hin c tnh oxi ho v tnh kh do c mt ca cu oxi -O-O-: O22- + 2e 2O-2 O22- + 2e O2 Tnh oxi ho Tnh kh

Hot tnh oxi ho th hin mnh hn nn ngi ta thng dng cc peoxit kim loi kim lm cht oxi ho trng thi nng chy: 3Na2O2 + Cr2O3 2Na2CrO4 + Na2O Hot tnh kh ch th hin khi cho cc peoxit phn ng vi cc cht oxi ho mnh nh KMnO4, K2Cr2O7: 2KMnO4 + 5Na2O2 + 8H2SO4 2MnSO4 + 5O2 + 5Na2SO4 + K2SO4 + 8H2O 1.5.1.1. Hidropeoxit (H2O2) a. Cu to - Tnh cht vt l Phn t H2O2 c cu ta gp khc

di lin kt dO-O = 1,48 ca dO-H = 0,95 v nng lng ca lin kt EO-O = 217,5kJ/mol, EO-H = 376,5kJ/mol. Do phn t khng i xng nn H2O2 c cc tnh ln. trng thi hi khng c hin tng trng hp phn t, nhng trng thi lng hin tng trng hp nh lin kt hidro xy ra mnh hn so vi vi nc. b. Tnh cht ho hc - H2O2 km bn hn so vi peoxit kim loi kim. nhit thng n b phn hu chm, nhng khi un nng, c nh sng hoc c cht xc tc (oxit ca cc kim loi nng: MnO2, V2O5, Fe2O3) s phn hu xy ra kh nhanh: H2O2 H2O + 1/2O214

H = - 23,6Kcal/mol

- H2O2 rt tinh khit v m c mi tng i bn. Mun lm n nh H2O2 ngi ta thm vo dung dch cc cht c ch nh H2SO4, H3PO4... v bo qun trong cc bnh polietilen hoc bng nhm rt tinh khit, hoc trong cc l thu tinh sm mu. - Dung dch long ca H2O2 c tnh axit yu H2O2 + H2O H3O+ + HO2pK = 11,6 Khi tng tc vi dung dch kim mnh, n cho peoxit v ngc li khi cho peoxit tc dng vi axit, H2O2 c gii phng: H2O2 + Ba(OH)2 BaO2 + 2H2O BaO2 + H2SO4 BaSO4 + H2O2 iu chng t rng BaO2 l mui ca axit H2O2 - Oxi trong H2O2 c mc oxi ho l -1, lm cho H2O2 va c kh nng oxi ha va c kh nng kh. Qua th in cc ca H2O2 trong dung dch, ta thy n l cht oxi ha mnh c trong mi trng axit v trong mi trng kim: H2O2 + 2H+ + 2e 2H2O H2O2 + 2e 2OHo = +1,77V o = +0,87V

Trong a s trng hp, phn ng oxi ha ca H2O2 trong mi trng axit xy ra chm v trong mi trng kim xy ra nhanh. N c th oxi ha c I- thnh I2, sunfua thnh sunfat, asen thnh asenic... H2O2 + 2KI + H2SO4 I2 + 2H2O + K2SO4 PbS + 4H2O2 PbSO4 + 4 H2O H2O2 cng th hin tnh kh: O2 + 2H+ + 2e H2O2 o = + 0,68V Tnh kh th hin khi tc dng vi nhng cht oxi ha mnh nh O3, KMnO4, Cl2: O3 + H2O2 H2O + 2O2 2KMnO4 + 3H2SO4 + 5H2O2 2MnSO4 + K2SO4 + 8H2O + 5O2 Cl2 + H2O2 + 2NaOH 2NaCl + O2 + 2H2O - Cng nh nc, H2O2 c th ng vai tr phi t to phc hidroperoxo v to cc peroxohidrat kt tinh. V d: [Fe(H2O)5(H2O2)]3+ ; Na2CO3.3H2O2 c. ng dng Tt c cc cng dng thc t ca H2O2 u da vo tnh khng bn v tnh oxi ha mnh ca n. Dung dch H2O2 3% c dng st trng trong y hc. Phn ln H2O2 c dng lm cht ty trng len, la, rm r, giy, my tre, lng... u im ca n l khi dng dung dch nng khng ln, n ty trng cc cht mu nhng khng lm h hng vt liu c ty. d. iu ch - Phng php thng c s dng trong cng nghip l in phn dung dch H2SO4 hoc hn hp (NH4)2SO4 + H2SO4 iu kin mt dng cao vi in cc Pt v nhit thp. C ch phn ng chung c vit nh sau:15

2HSO4- - 2e S2O82- + 2H+ 2SO42- - 2e S2O82- Axit peoxiisunfuric (H2S2O8) to ra khi in phn s kt hp vi nc cho H2O2: H2S2O8 + 2 H2O 2 H2SO4 + H2O2 Chng ct p sut thp s thu c H2O2 c nng cao hn. H2O2 cng c iu ch bng qu trnh oxi ha mt lot cc dn xut ca antraquinol:OH o2 O+H 2O2

OH

O

Antraquinol

Antraquinon

Antraquinon to thnh c kh bng H2 tr li thnh antraquinol a li dy chuyn sn xut. - Trong PTN, c th iu ch H2O2 bng phn ng H2SO4 vi BaO2.

16

CHNG 2. CC NGUYN T NHM IA (Li, Na, K, Rb, Cs, Fr)2.1. C IM CHUNG Nhm ny bao gm cc nguyn t: Li, Na, K, Rb, Cs v Fr. S d gi l kim loi kim v hidroxit ca chng l cht kim mnh. c im nguyn t ca cc nguyn t nhm IA Nguyn t S th t Electron ha tr Bn knh nguyn t () Bn knh ion X+ () NL ion ha Xo X+ (eV) Th in cc (V) Li 3 2s1 1,55 0,68 5,39 -3,02 Na 11 3s1 1,89 0,98 5,14 -2,71 K 19 4s1 2,36 1,33 4,34 -2,92 Rb 37 5s1 2,48 1,49 4,17 -2,99 Cs 55 6s1 2,68 1,65 3,89 -3,02 Fr 87 7s1 2,8 1,75 3,98

- Do c mt electron ha tr ns1 bn ngoi cu hnh bn ca kh tr nn cc nguyn t kim loi kim d dng mt electron ha tr to thnh M+. V th, kim loi kim l nhng kim loi in hnh nht. Mc oxi ha c trng ca chng l +1. - Kim loi kim phn ln to hp cht lin kt ion. Do tc dng phn cc khng ng k ca cc ion (in tch nh, tnh bn ca cu trc electron, kch thc ion M+ ln) nn s to phc ca K+, Rb+, Cs+, v Fr+ khng c trng, i vi chng ngay c cc hidrat tinh th cng hu nh cha bit. - Trong cc kim loi kim, Li chim mt v tr c bit so vi cc kim loi kim khc. V d: Li c th in cc m hn cc kim loi kim khc (-3,02V), mt s hp cht ca Li t tan hn so vi hp cht ca kim loi kim khc. 2.2. TNH CHT L HC - dng n cht, cc kim loi kim l nhng kim loi mu trng bc, ng nh (tr Cs c mu vng nh), nh kim bin mt nhanh khi tip xc vi khng kh, cc kim loi kim u kt tinh trong mng tinh th lp phng tm khi. Mt s hng s vt l ca kim loi kim Tnh cht Khi lng ring (g/cm3) cng (thang Mosh) To nng chy (C) To si (C) Li 0,53 0,6 179 1370 Na 0,97 0,4 98 883 K 0,86 0,5 63 760 Rb 1,53 0,3 38 700 Cs 1,87 0,2 28 670

- Nhit nng chy v nhit si u thp v gim dn t Li Cs l kt qu ca lin kt kim loi yu v lin kt cng yu dn khi kch thc nguyn t tng ln.17

- Cc kim loi kim u nh v mm: kim loi Li ni ln trn du ha, Na, K ni ln trn nc, tnh mm ca kim loi kim do lin kt kim loi yu trong mng li tinh th ca kim loi. Cc kim loi kim c dn in cao. - Cc kim loi t do cng nh cc hp cht d bay hi ca chng khi t trong ngn la khng mu lm cho ngn la c cc mu c trng: Nguyn t Mu Li tm Na Vng K Tm Rb Tm hng Cs Xanh da tri

Trong ha hc phn tch ngi ta da vo iu nhn bit ra cc kim loi kim hoc cc hp cht ca chng - Di tc dng ca tia t ngoi, cc kim loi Na, K, Rb, Cs phng ra electron, cng ca dng electron phng ra t l vi cng ca nh sng c hp th. Li dng tnh cht ny ngi ta dng kim loi kim nht l Rb v Cs lm t bo quang in. 2.3. TNH CHT HA HC Cc kim loi kim rt hot ng v mt ha hc, trong cc phn ng chng th hin tnh kh mnh v tnh kh tng ln u n t Li Cs. 2.3.1. Tc dng vi phi kim 2.3.1.1. Tc dng vi halogen Cc kim loi kim bc chy trong kh Cl2 khi c mt hi m nhit thng, vi Br2 lng K, Rb, Cs n mnh cn Na, Li ch tng tc trn b mt, vi I2 cc kim loi kim ch tng tc mnh khi un nng. 2M + X2 2MX 2.3.1.2. Tc dng vi oxi Khi c t nng trong khng kh hoc trong O2, Li to nn Li2O v mt t Li2O2 cn i vi cc kim loi khc, oxit ca chng tc dng tip tc vi O2 to thnh peoxit (Na2O2) hoc supeoxit (K2O, RbO2). Tc dng hn ch ca Li c gii thch l do ion Li+ c kch thc b nn khng c th lm bn nhng anion ln nh O2-. 2.3.1.3. Phn ng vi cc phi kim khc - Phn ng n cng xy ra khi nghin kim loi kim vi lu hunh: 2M + S M2S - Khi un nng vi N2, C, Si ch c Li l c th tc dng trc tip to nn Li3N, Li2C2, Li6Si2. 2.3.2. Tc dng vi hp cht 2.3.2.1. Tc dng vi H2O Cc kim loi kim c th in cc rt thp. c bit th in cc ca Li thp v ion Li c nng lng hidrat ha ln nht. Cc kim loi kim tng tc mnh lit vi H2O gii phng H2:+

2M + 2H2O 2MOH + H2 Khi tng tc vi H2O, Li khng cho ngn la, Na nng chy thnh ht trn ni v chy trn mt nc, K bc chy ngay, Rb, Cs gy phn ng n.18

2.3.2.2. Tc dng vi NH3 Khi un nng qu nhit nng chy trong kh NH3, kim loi kim tc dng vi NH3 to ra cc amidua 2Na + 2NH3 2NaNH2 + H2 2.4. TRNG THI THIN NHIN - IU CH - Do hot tnh mnh d b oxi ha nn khng gp kim loi kim trng thi t do. Trong cc kim loi kim th Na, K tn ti dng hp cht thin nhin nhiu hn: Nc bin (NaCl), mialit (Na2SO4.10H2O), cryolit (Na3AlF6), Borat (Na2B4O7.10H2O), xilit (KNO3 - NaNO3), spolitmen (LiAl(SiO3)2), Kali clorua (KCl), cacnalit (KCl.MgCl2.6H2O) - Phng php iu ch cc kim loi kim l in phn nng chy cc hp cht (mui hoc hidroxit) ca chng. 2.5. CC HP CHT CA KIM LOI KIM 2.5.1. Oxit 2.5.1.1. Oxit thng M2O - Tt c cc oxit M2O u l cht dng tinh th lp phng. Mu sc ca chng bin i t trng n da cam: Li2O trng Na2O trng K2O trng Rb2O vng Cs2O da cam

- Nhit nng chy, nhit si, bn gim dn t Li - Cs. Li2O tng tc chm vi nc cn cc oxit khc tc dng rt mnh: M2O + H2O 2MOH - Tr Li2O, tt c cc oxit khc tng tc vi O2 ngay nhit thng to nn peoxit: M2O + O2 M2O2 - Li2O tinh khit c th iu ch bng cch phn hy hidroxit, cacbonat hay nitrat 800C trong kh quyn H2. Cc oxit khc c iu ch bng cch un nng peoxit, hidroxit, nitrit hay nitrat vi kim loi kim tng ng. V d: 2NaOH + 2Na = 2Na2O + H2 2.5.1.2. Peoxit M2O2 - Supeoxit MO2 - Tt c cc peoxit v supeoxit u c mu t vng n da cam v hung: Na2O2 vng nht K2O2 vng RbO2 vng Cs2O2 vng KO2 vng RbO2 da cam CsO2 hung

- Ni chung chng kh bn vi nhit, khng phn hy khi nng chy, tt c u ht m mnh v chy ra khi trong khng kh, chng tc dng vi nc rt mnh gii phng H2O2 v c oxi (trong supeoxit): M2O2 + H2O 2MOH + H2O2 2MO2 + 2H2O 2MOH + H2O2 + O219

- Peoxit v supeoxit l cc cht oxi ha mnh, c th iu ch bng cch t chy kim loi kim trong oxi hay cho O2 kh sc qua kim loi kim mi iu ch trong NH3 lng. V d: cho O2 kh sc qua dung dch mi iu ch ca Cs trong NH3 lng ngi ta thu c Cs2O2 nhng nu tin hnh thi gian lu v nhit 30 - 50C s c CsO2. Peoxit quan trng l Na2O2 v supeoxit quan trng l KO2 a. Natri peoxit Na2O2 - L mt cht bt trng, khi ln tp cht c mu vng, nng chy 460C, si 660C v phn hy r rt 600C, tc dng mnh vi nc: 2Na2O2 + 2H2O 4NaOH + O2 nhit thp: Na2O2 + H2O 2NaOH + H2O2 - N cng tc dng vi kh CO, CO2 v dung dch ca kh CO2 trong nc: Na2O2 + CO Na2CO3 2Na2O2 + 2CO2 2Na2CO3 + O2 Na2O2 + H2O + CO2 Na2CO3 + H2O2 - Na2O2 l mt cht oxi ha mnh: nhng cht d chy nh rm, bng, bt than, bt S, Al, ete, C6H6... khi tip xc vi Na2O2 c th bc chy v gy n mnh. Trong ha hc phn tch hn hp Na2O2 - Na2CO3 c dng kh qung sunfua bng cch nu chy trong chn bc: 2FeS2 + 15Na2O2 Fe2O3 + 4Na2SO4 + 11Na2O b. Kali supeoxit K2O - K2O l mt cht dng bt mu vng ht m mnh v nng chy 440C. - N b phn hy gii phng O2 khi tc dng vi nc, kh CO2 v axit long: 4KO2 + 2CO2 2K2CO3 + 3O2 2KO2 + H2SO4 K2SO4 + H2O2 + O2 - Trong chn khng KO2 phn hy theo qu trnh: 4KO2 2O2 + 2K2O2 3O2 + 2K2O - KO2 l mt cht oxi ha rt mnh, n tc dng vi H2, C, CO, NO... 4KO2 + 2C = 2K2CO3 + O2 2KO2 + CO = K2CO3 + O2 2KO2 + 3NO = KNO3 + KNO2 + NO2 - KO2 c iu ch bng cch dng KNO3 oxi ha K hoc t chy K trong d O2 trong chn bc hoc Al. c. Ozonit MO3 - Ozonit quan trng nht l KO3, ozonit kali c to thnh khi cho O3 i qua KOH bt nhit t -5 -10C: 4O3 + 6KOH 4KO3 + 2KOH.H2O + O220

dng NH3 lng nhit -65C chit KO3 ta c dung dch mu , cho dung dch ny bay hi ta c nhng tinh th mu da cam ca KO3. - nhit thng KO3 khng bn phn hy cho KO2 v O2, 50 - 60C phn hy hon ton: 2KO3 2KO2 + O2 2.5.2. Hidoxit ca cc kim loi kim - Hidroxit kim loi kim l nhng baz mnh, d chy ra, tan tt trong nc. Tnh kim ca hidroxit kim loi kim tng t LiOH CsOH. trng thi nng chy chng n mn thy tinh, s nn nu chy chng phi dng cc dng c bng Fe, Ni, Ag. Khi un nng nhit cao hn cc hidroxit c th bay hi m khng mt nc. Ring LiOH mt nc 500C to ra Li2O. S d nh vy l v ion Li+ c kch thc b v c 2e nn ht mnh oxi t ion OH- trong LiOH hn nhng ion kim loi kim khc, tr LiOH cc MOH rt d tan vo nc. S ha tan cc MOH ta nhit, theo nguyn l Le Chatelier tan ca chng phi gim khi nhit tng ln nhng thc t tan ca NaOH, KOH vn tng theo nhit . Tht vy nhit thot ra khi ha tan hidroxit l nhit ca qu trnh hidrat ha cc kim loi kim. Hidroxit ca cc kim loi to nn cc hidrat c th tch ra dng tinh th. V d: KOH to nn cc hidrat nh KOH.H2O; KOH.2H2O v KOH.4H2O; KOH.2H2O bn nhit thng v qu trnh ha tan ca n hp th nhit. iu ny gii thch s bin i tan nh trn. - iu ch MOH c 2 cch: + Phn ng trao i gia Ba(OH)2, Ca(OH)2 vi sunfat ca kim loi kim: M2SO4 + Ba(OH)2 BaSO4 + 2MaOH + in phn dung dch MCl c mng ngn: 2MCl + 2H2O 2MOH + Cl2 + H2 2.5.3. Mui kim loi kim - Tt c cc mui ca kim loi kim u l hp cht ion, tinh th khng mu, d tan trong nc. Nhng mui c mu do mu ca anion gy nn. Mu ca ion kim loi sinh ra bi s hp th nhng lng t nh sng c nng lng tng ng khi electron nhy sang mc nng lng cao hn. i vi ion kim loi kim vi cu hnh electron rt bn ca kh tr, nng lng cn thit kch ng electron nhy ti cc obitan trng ngoi l rt ln. - Cc mui kim loi kim thng c nhit nng chy cao v dn in khi nng chy. a s u d tan trong nc, tr mt s mui ca Liti tng i kh tan. tan ca florua kim loi kim ph thuc vo nng lng mng li. Vi cc florua s gii phng nng lng hidrat ha ca cation nh hn s gim nng lng mng li. V vy tan ca florua kim loi kim tng t Li Cs. tan cc mui cha anion vi in tch > -1 nh PO43-, SO42-, CO32- bin i ging florua. NaCl iu ch t nc bin l cht ban u iu ch HCl, Na2SO4, Cl2, NaOH, cc ha phm cho x phng v sn xut thuc nhum. Ngoi tr Li2CO3 t tan, tt c cc mui M2CO3 cn li u tan tt trong nc. bn vng ca M2CO3 tng t Li2CO3 Cs2CO3. Ch c Li2CO3 phn hy trn 100C:21

Li2CO3 Li2O + CO2 C 2 loi cacbonat v hidro cacbonat, nhng mui ny d tan trong nc v d b thy phn: M2CO3 + H2O MOH + MHCO3 MHCO3 + H2O MOH + H2CO3 Trong nc MHCO3 cho mi trng kim yu hn M2CO3. tan NaHCO3 trong nc km hn Na2CO3. Na2CO3 cn gi l x a kt tinh, Na2CO3 nng chy 850C dng cho cng nghip dt, x phng, giy. iu ch Na2CO3 theo phng php Solvay (phng php amoniac): Ha tan NaCl vo dung dch NH3 n bo ha. Sau sc kh CO2 v dung dch. NaHCO3 kt ta v tan nh hn mui NH4HCO3: NH3 + CO2 + H2O NH4HCO3 NaCl + NH4HCO3 NaHCO3 + NH4Cl Lc v un nng 600C 2NaHCO3 Na2CO3 + CO2 + H2O cho NH3 vo dung dch cn li: NH4HCO3 + NH3 (NH4)2CO3 (NH4)2CO3 CO2 + H2O + 2NH3 thu NH3 t NH4Cl bng cch cho thm nc vi vo: 2NH4Cl + Ca(OH)2 CaCl2 + 2H2O + 2NH3 CO2 v NH3 li cho tr li qu trnh trn.

22

CHNG 3. CC NGUYN T NHM IIA (Be, Mg, Ca, Sr, Ba, Ra)3.1. C IM CHUNG Nhm IIA bao gm cc nguyn t Be, Mg, Ca, Sr, Ba v Ra. Chng cn c gi l kim loi kim th v cc oxit CaO, BaO, SrO tan c trong nc cho dung dch kim mnh v mt khc cc oxit c tan b v bn nhit cao ngha l c nhng tnh cht m cc nh gi kim thut ngy xa gi l th (t). c im nguyn t ca cc nguyn t nhm IIA Be S th t Cu hnh electron Bn knh ngt () Bn knh ion M2+ () I1 (Kcal/ntg) I2 (Kcal/ntg) Th in cc (V) 4 2s2 1,13 0,34 214,9 419,9 -1,85 Mg 12 3s2 1,6 0,74 176,3 346,6 -2,37 Ca 20 4s2 1,97 1,04 140,9 273,8 -2,87 Sr 38 5s2 2,15 1,2 131,3 254,3 -2,89 Ba 56 6s2 2,21 1,33 120,2 230,7 -2,9 Ra 88 7s2 2,35 1,14 121,7 234,9 -2,92

- Do c 2 electron ha tr ns2 ngoi cu hnh bn ca kh tr, cc nguyn t kim loi kim th d dng mt 2 electron to thnh ion M2+, chng l kim loi hot ng v hot tnh tng dn t Be Ra. So vi cc nguyn t kim loi kim cng chu k th kim loi kim th t hot ng hn v c in tch ht nhn ln hn v bn knh nguyn t nh hn. - Vic I2 ln hn nhiu so vi I1 cho thy dng nh cc kim loi kim th d to nn M+. Nhng trn thc t, nhiu phn ng c thc hin trong dung dch nn nng lng hidrat ha cao ca M2+ b p cho nng lng ion ha cao nn nguyn t kim loi kim th d mt 2 electron ha tr to ra M2+. - Trong cc hp cht, cc kim loi kim th ch c mc oxi ha +2. Be to nn ch yu nhng hp cht lin kt cng ha tr, cc nguyn t cn li ch yu to hp cht ion. 3.2. TNH CHT L HC - Cc kim loi kim th c mu trng bc hoc xm nht, trong khng kh Be, Mg vn gi c nh kim cn cc kim loi khc mt mu nh kim nhanh chng. Nhit nng chy, nhit si ca kim loi kim th ln hn kim loi kim. - Tr Be v Mg, cc kim loi kim th t do v cc hp cht d bay hi ca chng khi t trong ngn la khng mu s lm cho ngn la c mu c trng: Ca da cam Sr son Ba lc hi vng

Trong ha hc phn tch, da vo mu c trng ny nhn bit cc kim loi .23

Mt s tnh cht vt l quan trng ca kim loi kim th Be T trng (g/cm3) tnc (C) ts (C) dn in ring (.cm-1) 3.3. TNH CHT HA HC Cc kim loi kim th l nhng kim loi hot ng ng sau kim loi kim. Trong cc phn ng chng th hin tnh kh v tnh kh tng ln dn t Be Ra. 3.3.1. Tc dng vi hidro - Khi un nng, cc kim loi Ca, Sr v Ba tc dng d dng vi H2 to ra hidrua ion MH2. Chng hn: Ca + H2 CaH2150 o C

Mg 1,74 651 1107 25.104

Ca 1,6 851 1482 23.104

Sr 2,6 770 1880 3.104

Ba 3,75 710 1640 1,7.104

Ra 5 960 1140 -

1,85 1285 2970 28.104

- Cc hidrua ion ca kim loi kim th bn hn hidrua ion kim loi kim. 3.3.2. Tc dng vi oxi - Be, Mg chy trong khng kh to ra BeO v MgO: 2Mg + O2 2MgO - Ca, Sr, Ba nhanh chng b oxi ha trong khng kh to ra lp oxit mu vng nht. Khi c xt Ba c th bc chy. Mg khi chy cn pht ra nh sng chi giu tia t ngoi nn c dng lm pho sng. 3.3.3. Tc dng vi cc cht khc - Khi un nng, kim loi kim th tc dng mnh vi halogen, S, P, N2, C, Si. Khi kim loi kim th chy trong khng kh, ngoi oxit MO cn c nitrua M3N2: 3Mg + N2 Mg3N2 - Cc nitrua c pht hin do phn ng vi nc cho NH3: Mg3N2 + 6H2O 3Mg(OH)2 + 3NH3 Li dng kh nng d phn ng d phn ng vi O2, N2 ngi ta dng Ca vo vic loi O2, N2 ra khi cc kh tr. - Khi tc dng vi C, Be to ra Be2C gii phng CH4 khi thy phn, cn cc kim loi kim th khc to ra cacbua MC2 gii phng C2H2 khi b thy phn: 2Be + C Be2C Ca + C CaC2 Be2C + 4H2O 2Be(OH)2 + CH4 CaC2 + 2H2O C2H2 + Ca(OH)2 - Khi tc dng vi Si tt c cc kim loi kim u to ra cc silixua M2Si24

2Ca + Si Ca2Si - Do i lc mnh vi oxi, cc kim loi kim th khi un nng c th kh nhiu oxit bn nh B2O3, CO2, SiO2, TiO2, Al2O3, Cr2O3... 2Mg + CO2 2MgO + C 2Be + TiO2 2BeO + Ti - Do c th in cc b tng ng vi kim loi kim, cc kim loi kim th d dng tc dng vi H2O gii phng H2 v cng d vi axit. Thc t Be khng tan v Be(OH)2 khng tan trong nc, Mg khng tc dng vi nc lnh, tc dng chm trong nc nng. Ca + H2O Ca(OH)2 - Ring Be do c hidroxit Be(OH)2 lng tnh nn tan c trong dung dch kim mnh hay kim nng chy to ra mui berilat v gii phng H2: Be + 2NaOH + 2H2O Na2[Be(OH)4] + H2 Be + 2NaOH(nc) Na2BeO2 + H2 - Cng nh kim loi kim, cc kim loi Ca, Sr, Be c th tan trong NH3 lng cho dung dch mu xanh lam thm. V bn cht v tnh cht ha hc ca dung dch mu xanh lam ny ging dung dch kim trong NH3 lng, nhng khc ch sau khi NH3 bay hi th dung dch kim loi kim cho kim loi kim cn kim loi kim th li tinh th vng ng nh c thnh phn khng i l M(NH3)6 (M = kim loi kim th), khi un nng c mt xc tc ta thu c amidua: Ca(NH3)6 4NH3 + H2 + Ca(NH2)2Canxi hexaamin Canxi amidua

3.4. TRNG THI T NHIN - IU CH - Ngi ta thng gp cc kim loi ny dng nc bin, mui khong, dolomit CaCO3.MgCO3, cacnalit MgCl2.KCl.6H2O. - Nguyn tc chung iu ch kim loi kim th l in phn mui nng chy. Ngoi ra c th dng cc cht kh kh cc oxit hoc mui ca chng thnh kim loi: + Be c iu ch bng cch in phn hn hp BeCl2 v NaCl nng chy vi m cc bng Hg trong kh quyn Ar. + Mg c iu ch bng cch in phn nng chy mui MgCl2 tch t nc bin: Nung dolomit 900C: CaCO3.MgCO3 CaO + MgO + 2CO2 Ngm hn hp oxit trong nc bin ta thu c Mg(OH)2: CaO + H2O Ca(OH)2 Ca(OH)2 + Mg2+ Mg(OH)2 + Ca2+ T Mg(OH)2 MgCl2 sau in phn nng chy: MgCl2 Mg + Cl2 Ngoi ra, c th kh qung dolomit bng st silixua 1500C:25

CaCO3.MgCO3 + FeSi Mg + CO2 + Silicat Fe v Ca - iu ch Ca bng cch in phn nng chy hay kh bng Na: CaCl2 + 2Na 2NaCl + Ca + Rai l cht phng x hot ng mnh, sn phm phn hy ht nhn ca 238U. Trong luyn kim, Mg c dng iu ch kim loi sch, kh oxit kim loi. Hp kim Al - Mg tr khng tc dng vi kim, v c HF, khng b r. Hp kim 2% Mn, 98% Mg khng tc dng vi nc. Hp cht CaCO3, bt nh, Ca(OH)2 baz r tin, CaO dng cho thy tinh, xi mng, s... 3.5. CC HP CHT CA KIM LOI KIM TH 3.5.1. Oxit 3.5.1.1. c im chung Cc oxit MO l cht bt mu trng, khi nu chy trong l in ngui, chng s dng tinh th. BeO c mng li tinh th lc phng, cc oxit khc c mng li lp phng. V c nng lng mng li rt ln nn cc oxit MO rt kh nng chy v rt bn nhit, chng c th bay hi m khng b phn hy. V vy cc oxit MO dng lm vt liu chu la. Mt s c im ca cc oxit MO BeO Nng lng mng li (Kcal/mol) tnc (C) ts (C) 3.5.1.2. Tnh cht ha hc - BeO khng tan trong nc, MgO tan chm v rt t; cc oxit Ca, Sr, Ba tan d dng v phn ng ta nhiu nhit: MO + H2O M(OH)2 - Cc oxit CaO, SrO, BaO u ht m mnh v c kh nng hp th kh CO2: BaO + CO2 BaCO3 - MO l cc oxit baz, c th tan trong dung dch axit to ra mui: MO + HCl MCl2 + H2O ring BeO kh tan trong axit d tan trong dung dch kim to ra mui berilat BeO + 2NaOH Na2BeO2 + H2O BeO + 2HCl + 3H2O [Be(OH)2]Cl2 - nhit cao, cc MO c th b kim loi kim, Al, Si kh n kim loi. 3.5.1.3. ng dng Trong thc t BeO dng lm cht xc tc, chn nung, cng nghip thy tinh. MgO lm gch chu la, iu ch Mg kim loi, xi mng magie. CaO (vi sng) dng lm vt liu xy dng, iu ch CaC2...26

MgO 938 2800 3100

CaO 841 2570 3600

SrO 792 2460 2500

BaO 756 1925 2000

2252 4200

3.5.1.4. iu ch Nguyn tc chung ca phng php iu ch oxit MO l nhit phn mui cacbonat, nitrat hoc hidroxit ca kim loi kim th CaCO3 CaO + CO2 3.5.2. Peoxit - Tng t kim loi kim, cc cation kim loi kim th c bn knh ln nn c kh nng lm bn mt s anion ln nh peoxit, supeoxit. Be khng to nn peoxit; Mg ch to nn peoxit dng hidrat c ln peoxit MgO2; cn Ca, Sr v Ba to nn cc peoxit MO2 l cht bt mu trng kh tan trong nc khi un nng MO2 to ra MO v O2 MO2 MO + 1/2O2 - Cc MO2 u l cht oxi ha mnh, nhng khi tc dng vi cht oxi ha mnh hn chng l cht kh. MO2 c iu ch khi cho H2O2 tc dng vi dung dch hidroxit tng ng: Ca(OH)2 + H2O2 + 6H2O CaO2.8H2O CaO2.8H2O CaO2 + 8H2O ring BaO2, SrO2 c th iu ch bng cch cho oxit kt hp trc tip vi oxit 2BaO + O2 2BaO2 - Peoxit quan trng nht l BaO2 l mt cht bt mu trng nng chy 450C, phn hy 600C: 2BaO2 2BaO + O2 BaO2 kh tan trong nc, ru, ete nhng d tan trong dung dch axit long gii phng H2O2: BaO2 + HCl BaCl2 + H2O2 BaO2 + H2SO4 BaSO4 + H2O2 khi un nng BaO2 tng tc vi H2, S, C, NH3: BaO2 + H2 Ba(OH)2 BaO2 + S 2BaO + SO2 vi axit HCl c, gii phng kh Cl2: 4HCl + BaO2 BaCl2 + Cl2 + H2O BaO2 c th kh kim loi qu, nng thnh kim loi t do: HgCl2 + BaO2 Hg + BaCl2 + O2 3.5.3. Hidroxit M(OH)2 - Cc hidroxit M(OH)2 khan u dng bt mu trng. Be(OH)2, Mg(OH)2 rt kh tan, Ca(OH)2 tan tng i tt, Ba(OH)2 tan hon ton trong nc. M(OH)2 khng bn nhit khi un nng, mt nc to ra oxit, bn nhit tng ln t Be Ba: M(OH)2 MO + H2O27

- M(OH)2 l nhng baz, tnh baz tng ln t Be(OH)2 Ba(OH)2. Be(OH)2 l mt baz rt yu, Mg(OH)2 yu, Ca(OH)2, Sr(OH)2, Ba(OH)2 l nhng baz mnh. Cc M(OH)2 c kh nng hp th CO2, d tan trong axit to ra mui: Ba(OH)2 + CO2 BaCO3 + H2O Ba(OH)2 + HCl BaCl2 + H2O ring Be(OH)2 cn c kh nng tan trong dung dch kim hay dung dch cacbonat kim loi kim m c: Be(OH)2 + 2NaOH Na2[Be(OH)4] - Be(OH)2, Mg(OH)2 c iu ch bng cch cho dung dch kim tc dng vi dung dch mui: MgCl2 + 2NaOH Mg(OH)2 + 2NaCl BeCl2 + 2NH3 + 2H2O Be(OH)2 + 2NH4Cl Ss(OH)2, Ca(OH)2, Ba(OH)2 c iu ch bng cch cho oxit tc dng vi H2O: BaO + H2O Ba(OH)2 3.5.4. Mui ca kim loi kim th Cc mui kim loi kim th dng tinh th v khi tan to thnh dung dch khng mu. Cc mui halogenua, axetat, xianua, sunfua, tioxianat u d tan, mui florua kh tan, tr BeF2 d tan. Mui BeSO4 v MgSO4 tan, CaSO4, SrSO4, BaSO4 khng tan; cc mui CrO4-, C2O42-, PO43-, CO32- u t tan. 3.5.4.1. Halogenua kim loi kim th MX2 c nhit nng chy, nhit si kh cao, mt s phn hy trc khi si. Cc halogen quan trng ca Be v Mg l BeCl2 v MgCl2, chng tan tt trong nc. - BeCl2 l hp cht polime c cu trc mch di: Cl Cl Cl Be Be Cl Cl Cl Be Be Cl Cl Cl Be

Cl Trong nhng mt Be Cl28

Be

vung gc vi nhau. Mi nguyn t Be ni

vi hai nguyn t Cl bng lin kt cng ha tr v vi hai nguyn t clo khc bng lin kt cho nhn. BeCl2 c iu ch bng cch cho kh Cl2 kh i qua hn hp BeO v C un nng 900C: Cl2 + BeO + C BeCl2 + CO - MgCl2 c iu ch t nc bin (nc t ca qu trnh sn xut mui n), MgCl2 khan c th iu ch bng cch cho Cl2 tc dng trc tip vi Mg: Cl2 + Mg MgCl2 dung dch MgCl2 30% trn vi bt MgO nung to thnh khi nho ng cng sau vi gi gi l xi mng magie. Trong ch yu to nn hp cht cao phn t c cu trc mch di: Cl - Mg -O - Mg O - Mg - OH - Cc clorua kim loi kim th khc c iu ch nh sau: MCO3 + 2HCl MCl2 + H2O + CO2 - Mun c CaCl2 khan c to ra bng cch nung nng CaCl2.6H2O 260C. CaCl2 khan l mt cht ht m, cht lm kh kh. Dung dch CaCl2 dng tri mt ng cho khi bi, trong phng th nghim BaCl2 dng pht hin ion SO42-. 3.5.4.2. Mui sunfat kim loi kim th - Cc mui sunfat MSO4 l nhng cht rn dng tinh th. BeSO4 v MgSO4 tan rt nhiu trong nc cn cc sunfat khc t tan trong nc, nht l BaSO4. - Mui sunfat thng ngm 2 phn t nc MSO4.2H2O, cc mui sunfat quan trng l CaSO4, BaSO4, MgSO4. - Thch cao CaSO4.2H2O khi nung 160 170C to thnh dng semi thch cao: 2(CaSO4.2H2O) 2CaSO4.H2O + 3H2O Bt 2CaSO4.H2O nho vi nc c khi nho, sau vi gi ng cng li thnh thch cao. Thch cao dng lm cht kt dnh, nn tng, b bt, ph gia cho xi mng. - BaSO4 km tan nht, c dng xc nh nh tnh Ba2+, v nh lng SO42-. N l cht cn quang chp Rnghen d dy. MgSO4.7H2O dng lm cht nhun trng. 3.5.4.3. Mui cacbonat ca cc kim loi kim th - MCO3 l cht rn dng tinh th. Tr BeCO3, cc mui cacbonat khc u t tan trong nc, nn chng tn ti t do trong thin nhin. - Khc vi mui cacbonat kim loi kim (M2CO3), cc mui MCO3 u khng bn vi nhit, bn nhit tng ln t Be Ba. - MCO3 tan c trong nc c cha kh CO2: MCO3 + H2O + CO2 M(HCO3)2 - Khc vi hidrocacbonat kim loi kim (MHCO3), cc M(HCO3)2 khng th tch ra trng thi t do m ch tn ti trong dung dch. Khi un nng, dung dch M(HCO3)2 chuyn thnh MCO3 kt ta: M(HCO3)2 MCO3 + H2O + CO229

- Mui cabonat quan trng trong thc t l CaCO3. Mui CaCO3 khi kt tinh t dung dch nng c dng nhng tinh th t phng, ngui chuyn dn sang dng mt thoi. CaCO3 rt t tan trong nc, 1 lt nc ho tan c 0,014g CaCO3. Mui CaCO3 b ho tan trong dung dch NH4Cl: CaCO3 + 2NH4Cl CaCl2 + 2NH3 + CO2 + H2O CaCO3 cng b ho tan trong nc c kh CO2 ho tan: CaCO3 + CO2 + H2O Ca(HCO3)2 y l phn ng n mn vi trong thin nhin, do vy trong nc sng thng c mt lng Ca(HCO3)2. Khi un nng Ca(HCO3)2 phn hy Ca(HCO3)2 CaCO3 + H2O + CO2 Phn ng ny gii thch s to thnh cc thch nh trong cc hang ng vi, hay s to thnh cn trong cc m un nc v ni hi. - CaCO3 phn hy 900C: CaCO3 CaO + CO2 - nhit cao n tc dng vi cc oxit nh SiO2, Al2O3, NO2 vi kh NH3: CaCO3 + SiO2 CaSiO3 + CO2 CaCO3 + 2NH3 Ca(CN)2 + 3H2O 3.6. Nc cng Nc trong thin nhin c cha mt lng mui tan ca Ca2+, Mg2+ gi l nc cng. cng ca nc c biu th bng s mili ng lng gam ca ion Ca2+ v Mg2+ c trong mt lt nc. cng ca nc c th dao ng trong mt gii hn tng i rng. Ngi ta chia cng lm 2 loi: - cng tm thi hay cng cacbonat: do mui Ca(HCO3)2, Mg(HCO3)2 gy ra. - cng vnh cu: do cc mui clorua, sunfat ca Mg, Ca gy ra. Tng s cng tm thi v cng vnh cu gi l cng chung. Nng (Ca2+ + Mg2+) (mE/l) 12 Loi nc mm Nc cng tm thi Nc cng Nc rt cng

Nu dng nc cng cho vo cc ni hi th trn thnh ni s to nn mt lp cn bm rt cht, lp cn ny lm gim truyn nhit ca thnh ni do lm tng s hao ph nhin liu. Mt khc v truyn nhit km nn lp cn ny lm cho thnh ni b nung nng ln rt mnh v c th lm n ni hi. Ngoi ra git bng nc cng s tn nhiu x phng, lu sch: 2RCOONa + Mg2+ (RCOO)2Mg + 2Na2+ - Lm mm nc cng tm thi: c th lm gim cng tm thi bng cch un nng: Ca(HCO3)2 CaCO3 + CO2 + H2O30

Tuy nhin, ngi ta thng kh cng tm thi bng cch thm Ca(OH)2, lng Ca(OH)2 thm vo c tnh ton t lng bicacbonat c trong dung dch: Ca(HCO3)2 + Ca(OH)2 CaCO3 + 2H2O - Lm mm nc cng vnh cu: bng cch thm Na2CO3, Na3PO4: CaCl2 + Na2CO3 CaCO3 + 2NaCl 3CaCl2 + 2Na3PO4 Ca3(PO4)2 + 6NaCl Trong thc t thng lm mm nc cng bng phng php trao i ion. Li dng kh nng c th trao i cation ca mt s hp cht cao phn t thin nhin v nhn to gi l ionit. Nhng cht c kh nng trao i cation gi l cationit, nhng cht c kh nng trao i anion gi l anionit. Mt cationit thng dng lm mm nc gi l zeolit c thnh phn l Na2Al2SiO8.xH2O, ion Na+ c trong mng li tinh th ca zeolit c kh nng di chuyn nht nh. Khi di nc cng qua cc ht zeolit, mt s ion Na+ i vo nc nhng ch cho cc ion Ca2+, Mg2+ v Fe2+ trong nc i vo zeolit qu trnh trao i cation xy ra nh sau: Na2Al2SiO8.xH2O + CaCl2 CaAl2Si2O8.xH2O + 2NaCl ti sinh li zeolit s dng ngi ta cho dung dch NaCl bo ha i qua zeolit: CaAl2Si2O8.xH2O + 2NaCl Na2Al2Si2O8.xH2O + CaCl2 Nh vy qu trnh lm mm nc bng zeolit ch tiu tn NaCl r tin. Mun loi tr c cation Ca2+ v anion ngi ta cho nc cng ln lt i qua 2 ct, mt ct ng cationit, mt ct ng anionit. Nha cationit l nhng hp cht cao phn t hu c c cha nhm axit, c cng thc chung l RCOOH (R- gc hu c phc tp) qua ct ny cc cation trong nc b gi li trong nc sinh ra axit: 2RCOOH + CaCl2 Ca(RCOO)2 + 2HCl Nha anionit l cc hp cht cao phn t hu c cha nhm baz c cng thc chung l RNH3OH, qua ct ny cc ion m b gi li: RNH3OH + HCl RNH3Cl + H2O Nhng nha ny sau khi c s dng c th c ti sinh bng cch cho ngm trong dung dch axit, kim. Ca(RCOO)2 + H2SO4 CaSO4 + 2RCOOH RNH3Cl + NaOH RNH3OH + NaCl

31

CHNG 4. CC NGUYN T NHM IIIA (B, Al, Ga, In, Tl)4.1. C IM CHUNG c im nguyn t ca cc nguyn t nhm IIIANguyn t B Al Ga In Tl Z 5 13 31 49 81 Cu hnh e nguyn t [He] 2s2 2p1 [Ne] 3s2 3p1 [Ar] 3d10 4s2 4p1 [Kr] 4d10 5s2 5p1 [Xe] 4f14 4d10 6s2 6p1 Nng lng ion ha (kcal/ntg) I1 191 138 138 133 141 I2 580 434 473 435 4712 1

I3 870 655 708 646 687

I4 5980 2767 1480 1250 1170

Th in cc (V) - 1.66 - 0.53 - 0.34 + 0.72

- Cu hnh electron ha tr ca cc nguyn t l ns np . Cc nguyn t B v Al ng ngay sau cc kim loi kim th nn lp electron st ngoi gm 2 v 8 electron tng ng. Cc nguyn t Ga, Ni v Tl ng sau dy nguyn t chuyn tip nn lp electron st ngoi gm 18 electron. Vi cu hnh electron nh vy nn cc nguyn t trong nhm IIA khng ging nhau nhiu nh cc nguyn t kim loi kim v kim th. - Nng lng ion ha th nht I1 ca B tng i ln, I2 v I3 cng ln hn na. V th nng lng cn thit to nn ion B3+ ln hn nhiu so vi nng lng mng li ca cc hp cht ion hoc nng lng hidrat ha ca chng trong dung dch. V th B khng d dng mt 3e to thnh ion B3+ m ch c khuynh hng to lin kt cng ha tr m thi. - Khuynh hng to ion M+3 tng ln r rt Al, trong khi B l nguyn t phi kim th Al l kim loi hot ng. - T Al n Ga tnh kim loi hi gim xung v Ga ng sau kim loi chuyn tip nn chu s co rt d. T Ga n In tnh kim loi hi tng ln, nhng t In n Tl tnh kim loi gim xung v Tl ng sau h Lantanoic nn chu s co rt f. - Trong cc hp cht, cc nguyn t nhm IIIA c mc oxi ha ch yu l +3. Tuy nhin do I1 b hn tng I2 v I3 nn cc nguyn t Al, Ga, In, Tl cn c mc oxi ha +1. bn ca mc oxi ha +1 tng ln t Al n Tl. i vi Tl th mc oxi ho +1 tri hn mc +3. - B khng to nn cation trong dung dch nn th in cc ca n khng xc nh c. Cc nguyn t cn li c th in cc b hn kim loi kim v kim th. - V nhiu mt th B ging nhiu vi Si IVA hn l ging vi Al v cc nguyn t khc trong cng nhm. 4.2. BO 4.2.1. Tnh cht - B tn ti di mt s dng th hnh: tinh th v v nh hnh. B tinh th tinh khit khng mu, nhng thng c mu en xm v thng ln tp cht borua cc kim loi.32

N c nh kim v b ngoi ging nh kim loi. B dng v nh hnh v tinh th l nhng cht bn dn, dn in tng theo nhit . - iu kin thng B rt tr v mt ha hc, n ch tng tc trc tip vi F. Khi un nng n tng tc vi nhiu nguyn t. + 700C, B chy trong khng kh phn ng pht nhiu nhit: 4B + 3O2 2B2O3 H = - 176 kcal/mol + 1200C, B tng tc vi N2 to thnh bo nitrua (BN) v 2800C vi cacbon to thnh bo cacbua (B12C3) + nhit thng, B khng tan trong nc, nhng nhit cao n tng tc vi hi nc to nn oxit v gii phng hidro: 2B + 3H2O B2O3 + 3H2 + B cng khng tan trong dung dch HCl v HF, dng bt mn n tan chm trong trong dung dch m c ca HNO3, H2SO4, H2O2 v mt s cht oxi ha mnh khc bin thnh H3BO3: B + 3HNO3 H3BO3 + 3NO2 + dng bt mn, B c th tan trong dung dch kim c nng hoc kim nng chy. Chng hn: 2B + 2NaOH + 2H2O 2NaBO2 + 2H2 + Khi un nng trong kh quyn NH3 hoc NO, B cng to thnh BN: 2B + 2NH3 2BN + 3H2 5B + 3NO 3BN + B2O3 4.2.2. Trng thi thin nhin v phng php iu ch - B l nguyn t tng i ph bin trong v qu t. Khong vt chnh ca B l borat (Na2B4O7.10H2O). - iu ch B vi tinh khit cao, ngi ta dng Mg kh B2O3 nhit cao: B2O3 + 3 Mg 2 B + 3 MgO Hn hp sau phn ng c ra bng kim, HCl v HF. Ngoi ra c th dng Na kh kali tetraborat nhit cao: KBF4 + 3 Na B + KF + 3 NaF 4.2.3. Cc hp cht quan trng 4.2.3.1. Boran Trong thc t khng c nhng bo hidrua nh BH3, B2H4, B3H5... iu ny l do trong cc hp cht B cha c bo ha v s phi tr v trng thi lai ha sp2 ca B khng c lm bn thm nh lin kt khng nh ch nh trong cc hp cht BF3, BCl3... S bo ha v s phi tr c th t c khi cc phn t bo hidrua trn kt hp li vi nhau to thnh nhng phn t nh B2H6, B4H10... Cc bo hidrua ny gi chung l boran. a. Cu to ca B2H633

Tng s electron trong phn t B2H6 l 12, khng to thnh 8 lin kt cng ha tr bnh thng, mi lin kt do 1 cp electron m nhn. Ngi ta ni rng diboran l hp cht thiu electron. Phn t diboran gm 2 nhm t din lch BH4 ni vi nhau qua mt cnh chung. Hai nguyn t B v 4 nguyn t H 2 u cng nm trn mt mt phng cn 2 nguyn t H cu ni nm trn v di mt phng v i xng nhau. Lin kt ca cc nguyn t H 2 u v nguyn t B l lin kt cng ha tr bnh thng c to nn bi orbital lai ha sp3 ca B, trn mi orbital c 1 electron c thn xen ph vi orbital 1s ca H cng c 1 electron c thn. Lin kt gia mi nguyn t H ca cu ni vi 2 nguyn t B (B H B) l kiu lin kt c bit, ngha l y c 2 lin kt nhng ch c 1 cp electron. Theo phng php MO th lin kt cng ha tr bnh thng l lin kt 2 tm, cn lin kt B H B l lin kt 3 tm. Trong phn t B2H6 c 2 lin kt 3 tm. Mi lin kt c hnh thnh nh s che ph ca 2 orbital lai ha sp3 ca 2 nguyn t B, 1 orbital c electron c thn, cn 1 orbital khng cha electron vi 1 orbital 1s ca nguyn t H cu ni c 1 electron c thn. Ba orbital t hp thnh 3 orbital phn t: lin kt, khng lin kt v phn lin kt; cp electron chung c phn b trn MO lin kt.

SPLK

KLK 1s

sp3 sp3

Slk

Gin nng lng ca cc MO ca mt lin kt 3 tm trong B2H6 b. Tnh cht - iu kin thng B2H6 v B4H10 l cht kh; B5H9, B5H11 v B6H10 l cht lng, cn li l cht rn. Tt c cc boran u c mi kh chu v rt c. - Cc boran l hp cht km bn v hot ng v mt ha hc. Khi un nng, chng phn hy thnh nguyn t. Tt c cc boran khi gp khng kh u bc chy, phn ng pht nhiu nhit: B2H6 + O2 B2O3 + H2O H = - 428 kcal Cc sn phm chy to ra c khi lng b hn nn boran c dng lm nhin liu tn la. - Boran tng tc mnh vi halogen v b halogen thay th dn hidro: B2H6 + Cl2 B2H5Cl + HCl34

Khi d Cl2 th hidro c th b thay th hon ton: B2H6 + Cl2 BCl3 + HCl - Tt c cc boran u b nc v dung dch kim phn hy thnh axit boric hay mui borat: B2H6 + H2O H3BO3 + H2 - Diboran cn c th tng tc vi nhiu hp cht nh hidrua kim loi kim, CO, NH3: B2H6 + NaH NaBH4 (natri borohidrua) Vi NH3, diboran to nn hp cht tinh th mu trng c thnh phn B2H6.2NH3. Dung dch ca hp cht ny trong NH3 lng dn in nn c l cng thc phn t ca hp cht l: H2N(NH3)2]+[BH4]-. Khi un nng n 200C hp cht ny bin thnh borazol B3N3H6. l mt cht lng khng mu, c khi lng phn t v cu to ging vi benzen, do c tnh cht ging vi benzen nn ngi ta thng gi l benzen v c. 4.2.3.2. Oxit boric B2O3 c 2 dng th hnh: dng thy tinh v dng tinh th. B2O3 dng thy tinh l cht dng khi rn, khng mu v gin. Khi un nng n tr nn do ri to thnh khi nht, c th ko si v ha lng 600C. B2O3 dng thy tinh c cu to bi cc nhm BO3 ni vi nhau qua nguyn t O v sp xp mt cch hn n. Dng tinh th c cu trc hon ton khc, gm nhng t din lch BO4 ni vi nhau qua nhng nguyn t O. Trong 4 nguyn t O th c 1 nguyn t O chung cho 2 t din v 3 nguyn t O cn li chung cho 3 t din. - B2O3 rt bn vi nhit, n bt u si 1800C. Khi nung nng, than khng d dng kh c B2O3 thnh B - B2O3 ht m rt nhanh v tan trong nc to thnh H3BO3: B2O3 + H2O H3BO3 4.2.3.3. Axit boric - Axit boric l cht dng tinh th trong sut v c mu trng. N tan va phi trong nc, qu trnh ha tan thu nhiu nhit. Do tan ca H3BO3 tng nhanh theo nhit , ngi ta d dng kt tinh li H3BO3 dng rn. - Khi un nng H3BO3 (orthoboric) mt dn nc v 100C to thnh axit metaboric HBO2 v khi nhit cao hn na th bin thnh B2O3: H3BO3to - H2O

HBO2

to - H 2O

B 2O 3 Ka = 10-9.

- Tuy trong cng thc H3BO3 nhng axit octhoboric l axit mt nc v rt yu, yu hn c axit H2CO3: H3BO3 + H2O [B(OH)4]- + H+ 4.3. NHM 4.3.1. Tnh cht l hc - Nhm l kim loi mu trng bc, khi lu trong khng kh n tr nn xm do to thnh mng oxit mng trn b mt.35

- Nhm l kim loi dn in v dn nhit tt. B mt ca nhm trn v bng c kh nng phn chiu tt nh sng nn ngi ta thng dng nhm trng ln b mt ca gng phn chiu trong cc knh vin vng. - Nhm c kh nng to c nhiu hp kim vi cc kim loi khc, quan trng nht l duyra (94% Al, 4% Cu, 2% Mg, Mn, Fe v Si). Duyra ngoi u im l nh nh nhm, nhng c nhng tnh cht c l tt hn nhm. 4.3.2. Tnh cht ha hc - Khc vi B, Al l kim loi hot ng (do bn knh nguyn t ln hn B). iu kin thng Al b ph lp oxit Al2O3 rt mng (0,00001mm) v bn lm cho Al tr nn km hot ng. Trong thc t n khng b g v bn vi nc... - Dy nhm hay l nhm dy khng chy khi c t nng mnh m nng chy trong mng oxit to thnh nhng ti bn trong l nhm lng v bn ngoi l oxit. L nhm mng khi t mnh s chy sng chi v pht nhiu nhit. 4 Al + 3 O2 2 Al2O3 H = - 399 kcal/mol - Tm nhm khi c nhng trong dung dch mui thy ngn hoc thy ngn kim loi th s b oxi ha n cng v khng c mng oxit bo v. - Do i lc ln i vi oxi nn nhm l cht kh mnh, nhit cao n d dng kh nhiu oxit kim loi n kim loi t do: Al + Cr2O3 Al2O3 + 2Cr Trong thc t ngi ta dng phng php ny iu ch nhng kim loi kh b kh v kh nng chy nh Fe, Cr, Mn, Ni, Ti, Zr, V... - Al tuy c tng nng lng ion ha I1, I2 v I3 kh ln (1230 kcal/mol) nhng nh ion Al3+ c nng lng hidrat ha rt ln (1100 kcal/iong) nn Al kim loi d dng chuyn thnh Al3+ trong dung dch Al3+(dd) + 3e Al (r) Eo = - 1,66V Tuy c th in cc thp, v mt nguyn tc Al d dng y hidro ra khi nc nhng do mng oxit bn bo v nn Al khng tc dng vi H2O, khng tc dng vi dung dch long ca axit H3PO4 v CH3COOH. Al ch d dng tan trong dung dch long ca axit HCl v H2SO4. Phn ng chung ca Al khi tan trong dung dch axit l: 2Al + 6H3O+ + 6H2O 2[Al(H2O)6]3+ + 3H2 Trong axit HNO3 v H2SO4 m c ngui th Al b th ng ha. - Tng t Be, Al tan trong dung dch kim mnh gii phong H2: 2Al + 2OH- + 6H2O 2[Al(OH)4]- + 3H2 4.3.3. Trng thi thin nhin v phng php iu ch - Al l mt trong nhng nguyn t ph bin nht. Phn ln Al tp trung vo alumosilicat: octhoclaz (K2O.Al2O3.6SiO2 ), caolinit (Al2O3.SiO2.2H2O )... Hai khong vt quan trng ca Al trong cng nghip l boxit (Al2O3.nH2O ) v cryolit (Na3AlFl6). - Gia th k XIX, phng php sn xut Al ch yu l dng kim loi kim kh mui AlCl3 hoc NaAlCl4 trng thi nng chy. Do gi thnh ca Al rt cao:36

AlCl3 + 3Na Al + NaCl NaAlCl4 + Na Al + NaCl - Cui th k XIX, Al mi c sn xut quy m cng nghip bng phng php in phn hn hp Al2O3 (6 8%) v Na3AlF6 (92 94%) nng chy. + Qung boxit cha nhiu tp cht, tinh ch ngi ta un nng bt boxit trong dung dch NaOH 40% 150C di p sut 5 6 atm. Khi : Al2O3 + 2NaOH + 3H2O 2Na[Al(OH)4] Lc ly dung dch v pha long th Al(OH)3 s kt ta lng xung: Na[Al(OH)4] Al(OH)3 + NaOH Lc ly kt ta v nung nhit cao ta c Al2O3 tinh khit. + Cryolit trong t nhin kh him nn ngi ta thng iu ch bng cch ha tan Al(OH)3 v Na2CO3 trong dung dch HF: 2Al(OH)3 + 12HF + 3Na2CO3 2Na3[AlF6] + 9H2O + 3CO2 C ch qu trnh in phn Al2O3 trong cryolit n nay vn cha xc nh dt khot. Ngi ta cho rng: cryolit l hn hp ca AlF3 v NaF, khi in phn th ch c NaF b in phn to Na v F2. Na sinh ra s tc dng vi Al2O3 to thnh Al kim loi v mui NaF, cn F2 s y oxi trong Al2O3 to thnh AlF3. V th nng cryolit trong bnh in phn khng thay i. 4.3.4. Mt s hp cht quan trng 4.3.4.1. Nhm hidrua - Nhm hidrua l hp cht polyme (AlH3)n. N l cht rn v nh hnh, mu trng, khng bay hi v phn hy nhit trn 105C v to thnh nguyn t. - Tng t bo hidrua, nhm hidrua l hp cht thiu electron. N c cu trc lp, mi nguyn t Al c bao quanh bi 6 nguyn t H theo kiu bt din. Mi nguyn t Al ni vi 3 nguyn t Al bn cnh bng nhng lin kt 3 tm qua mt nguyn t H nh lin kt 3 tm trong diboran. - Nhm hidrua l hp cht rt nhy i vi O2 v H2O, n bc chy trong khng kh. Khi tan trong dung dch ete n d dng kt hp vi hidrua kim loi kim to thnh hidroxialuminat: n LiH + (AlH3)n n Li[AlH4] Li[AlH4] l cht kh mnh, n thng c dng trong cc phn ng tng hp hu c. - nhit thp, nhm hidrua d dng kt hp vi nhng cht cho electron nh NH3, MNH2, M2NH, M3N (M l kim loi kim), N(CH3)3: (AlH3)n + n NH3 n AlH3.NH3 4.3.4.2. Nhm oxit (Al2O3 ) - nhit thng, corundum rt tr v mt ha hc, khng tan trong nc, axit v kim. Nhng 1000C n tng tc mnh vi hidroxit, cacbonat, hidrosunfat v disunfat kim loi kim trng thi nng chy:37

Al2O3 + Na2CO3 NaAlO2 + CO2 Al2O3 + K2S2O7 Al2(SO4)3 + K2SO4 - nhit cao Al2O3 tng tc vi mt s oxit kim loi to nn nhng sn phm c tnh cht ging nh ngc chng hn: spinen MgO.Al2O3, alexandrit BeO.Al2O3 - Trong thc t Al2O3 c dng lm vt liu chu la, sn xut Al... - Trong cng nghip Al2O3 c iu ch bng cch nung Al(OH)3 nhit 1200 1400C: Al(OH)3 Al2O3 + H2O 4.3.4.3. Nhm hidroxit (Al(OH)3 ) - Nhm hidroxit c to nn khi hidroxit kim loi kim tc dng vi mui nhm, l kt ta nhy trng, thc t khng tan trong nc. Bng phng php thc nghim (nhiu x tia X), ngi ta nhn thy rng n khng c cu trc tinh th. lu n mt nc dn, sy kh ri nung n khi lng khng i to thnh oxit Al2O3. Nh vy kt ta nhy trng ca hidroxit nhm thc cht l Al2O3.nH2O. - Al(OH)3 c to ra khi cho kh CO2 sc qua dung dch NaAlO2, tinh th ny chnh l tinh th hidroxit nhm trong t nhin l gipxit (hidragilit). Hidragilit gm nhng tinh th n t v cu trc lp. Mi lp gm 2 mt cha cc nhm OH v nhng nguyn t Al nm gia 2 lp . Mi nguyn t Al c 6 nhm OH bao quanh. Hidragilit bn nhit di 150C, n c trong thnh phn ca nhiu loi boxit. - Nhm hidroxit l cht lng tnh in hnh, khi mi kt ta n d dng tan trong axit v kim: Al(OH)3 + 3H3O+ [Al(H2O)6]3+ Al(OH)3 + OH- + 2H2O [Al(OH)4(H2O)2]Anion [Al(OH)4(H2O)2]- thng vit gn di dng [Al(OH)4]- gi l ion aluminat. Mui khan thu c khi lm bay hi dung dch natri aluminat l NaAlO2. Mui ny bi thy phn rt mnh, trong dung dch long s b thy phn hon ton. V th khi sc kh CO2 vo dung dch NaAlO2 th s thu c Al(OH)3. 4.3.4.4. Nhm halogennua Cc hp cht nhm halogenua khc nhau nhiu v cu to cng nh tnh cht. Nhm florua c cu trc ion, nhm bromua v iodua mi trng thi u gm nhng phn t Al2Br2 v Al2I2, nhm clorua trng thi rn c kin trc ion, nhng trng thi kh v trng thi tan gm nhng phn t Al2Cl6. a. Nhm florua - Nhm florua l cht dng tinh th, c mu trng, nng chy 1290C. - N rt tr v mt ha hc, khng tan trong nc, axit v baz. N ch d dng kt hp vi florua kim loi to thnh cc floroaluminat kim loi c cng thc chung l M[AlF4], M2[AlF5], M3[AlF6] trong M l kim loi kim. Quan trng nht l cryolit Na3[AlF6]. - Nhm florua c iu ch bng cch cho Al hay Al2O3 tng tc vi kh HF: Al + HF AlF3 + H238

Al2O3 + HF AlF3 + H2O b. Nhm clorua - Nhm clorua l cht rn dng tinh th mu trng, n thng ng mu vng v cha tp cht FeCl3. Nhm clorua trng thi kh cng nh trng thi tan dng dime Al2Cl6. Cl Cl2,12 2,06 80C

Cl

Al Cl

Al Cl

Cl Cu trc phn t Al2Al6 Mi mt lin kt Al Cl Al khng cn phi m t nh lin kt 3 tm nh trong diboran m c th coi l mt lin kt cng ha tr bnh thng v mt lin kt cho nhn m Cl l nguyn t cho. - Phn t Al2Cl6 ny phn ly hon ton thnh nguyn t 800C. - Nhm clorua bc khi kh mnh trong khng kh v n ht m mnh ri thy phn gii phng HCl, v th cn bo qun nhm clorua trong l kn. N ha tan mnh trong nc ng thi ta nhit mnh, dung dch c mi trng axit: AlCl3 + H2O Al(OH)3 + HCl - AlCl3 kt hp d dng vi clorua kim loi kim to thnh cloroaluminat c cng thc chung l M[AlCl4], M2[AlCl5], M3[AlCl6] trong M l kim loi kim. - Mui khan d dng kt hp vi NH3, H2O, PCl5 v mt s hp cht hu c. V vy n c dng rng ri trong tng hp hu c. - Di tc dng ca kh O2 kh, mui khan b phn hy gii phng Cl2: Al2Cl6 + O2 Al2O3 + Cl2 - 1000C n tng tc vi Al kim loi to thnh mui Al c mc oxi ha thp hn: Al2Cl6 + 4Al 6AlCl - Nhm clorua khan c th iu ch bng cch cho kh Cl2 tng tc vi bt Al 500 550C hoc vi hn hp Al2O3 v than 1000C: Cl2 + Al2O3 + C AlCl3 + CO 4.3.4.5. Nhm sunfat v phn nhm - Nhm sunfat Al2(SO4)3 khan l cht bt mu trng, n phn hy nhit trn 770C. T dung dch nc n kt tinh dng hidrat Al2(SO4)3.18H2O. - Nhm sunfat c th kt hp vi sunfat kim loi kim to thnh mui kp M2SO4.Al2(SO4)3.24H2O thng gi l phn nhm. Phn l mt loi mui c cng thc chung M2SO4.E2(SO4)3.24H2O trong M (K, Na, Rb, Cs, NH4...), E (Al, Cr, Fe,39

Ga, In, Tl, Co). Chng ng hnh vi nhau v to nn nhng tinh th bt din. c s dng nhiu hn c trong thc t l phn nhm kali K2SO4.Al2(SO4)3.24H2O, phn crom kali K2SO4.Cr2(SO4)3.24H2O v phn st amoni (NH4)2SO4.Fe2(SO4)3.24H2O. - Nhm sunfat v phn nhm kali c nhng cng dng ch yu ging nhau trong cng nghip giy, nhum, thuc da v lm trong nc. Nhng cng dng ny xut pht t ch mui nhm thy phn kh mnh trong nc to thnh hidroxit nhm. Khi nhum vi, hidroxit nhm b vi hp th v gi cht trn si s kt hp vi phm nhum to thnh mu bn, nn n c gi l cht cn mu. Tc dng lm trong nc l do hidroxxit nhm hp th cht l lng v vi khun trong nc lm cho chng cng lng xung di. Trong cng nghip giy, nhm sunfat hay phn nhm c cho vo bt giy cng vi mui n. Nhm clorua to nn do phn ng trao i, b thy phn mnh hn to thnh hidroxit. Hidroxit ny s kt dnh nhng si xenluloza vi nhau lm cho giy khng b nhe mc khi vit. - Phn nhm kali c iu ch bng cch cho kt tinh t hn hp dung dch Al2(SO4)3 v K2SO4 cng nng . 4.4. CC NGUYN T Ga, In V Tl 4.4.1. Tnh cht vt l - trng thi t do Ga, In l nhng kim loi c mu trng bc, Tl c mu xm xanh. Tt c u c nhit nng chy thp. - Ga v In u c tnh cht phn chiu tt nh sng nn c dng trng gng, c bit l In l kim loi khng th thiu c trong lnh vc sn xut knh thin vn chnh xc. - Cng nh Al, cc kim loi Ga, In v Tl d to nn hp kim vi cc kim loi khc. V d: hp kim gm 18,1% In, 41% Bi, 22,1% Pb, 10,5% Sn v 8,2% Cd nng chy 47C c dng b xng trong nhng trng hp phc tp 4.4.2. Tnh cht ha hc - Ging vi Al, cc kim loi Ga, In bn trong khng kh v c mt lp oxit bn bo v cn Tl b oxi ha chm. - Khi un nng, Ga, In v nht l Tl tng tc mnh lit vi O2 v S. - Vi Cl2 v Br2 chng tng tc mnh lit nhit thng, i vi I2 th cn phi un nng. - Ga v In tan d dng trong dung dch HCl v H2SO4 nhng Tl tng tc chm v trn b mt to thnh lp mui kh tan bo v. Ngc li, trong HNO3 th Ga phn ng rt chm trong khi Tl phn ng rt mnh. - Ging vi Al, Ga cng tan trong dung dch kim to mui galat: Ga + OH- + H2O [Ga(OH)4]- + H2 Nu khng c cht oxi ha th In v Tl khng tan trong kim. Ga c th tan r rt trong dung dch NH3. 4.4.3. Trng thi t nhin v phng php iu ch - Trong thin nhin cc nguyn t Ga, In v Tl u t ph bin v rt phn tn, chng khng c nhng khong vt ring m thng di dng tp cht trong mt s40

qung ca cc kim loi Al, Zn, Fe v Cu. Nguyn liu chnh sn xut Ga l qung boxit, In l sunfua ca cc kim loi Zn, Pb v Cu cn Tl l qung pyrit FeS2. - Qu trnh iu ch kh phc tp, sau nhiu ln ch ha qung v tinh ch, ngi ta tch ra c oxit hoc clorua ri in phn dung dch mui clorua hoc dng kh H2 kh oxit ca chng. 4.4.4. Cc hp cht c mc oxi ha +3 4.4.4.1. Oxit (M2O3) - Cc oxit M2O3 u l cht rn, Ga2O3 mu trng, In2O3 mu vng cn Tl2O3 mu hung. Ph hp vi gi tr sinh nhit: Oxito H S (Kcal/mol)

Al2O3 - 399

Ga2O3 - 285

In2O3 - 222

Tl2O3 - 120

Ga2O3 nng chy 1740C khng phn hy, In2O3 nng chy 850C v chuyn thnh In3O4 cn Tl2O3 bt u mt oxi 100C v bin thnh Tl2O. V vy khi t nng trong khng kh Tl to nn hn hp Tl2O3 v Tl2O. - Tt c cc M2O3 u khng tan trong nc, dung dch kim v dung dch axit tr Tl2O3 tan c trong axit - Tr Tl2O3, tt c cc oxit M2O3 cn li u c th iu ch bng cch t chy kim loi trong khng kh. Ngoi ra c 3 oxit u c th iu ch bng cch nhit phn hidroxit hay mui nitrat: 4Ga(NO3)3 2Ga2O3 + 12NO2 + 3O2 4.4.4.2. Hidroxit M(OH)3 - Cc hidroxit ny l kt ta nhy, thc t khng tan trong nc v c thnh phn khng xc nh. Gali hidroxit c mu trng tn ti 2 dng Ga(OH)3 v GaOOH, indi hidroxit ch c mt dng In(OH)3 c mu trng v tali hidroxit c mu hung tn ti 2 dng Tl(OH)3 v TlOOH. Khi un nng nh, huyn ph Tl(OH)3 chuyn thnh TlOOH v khi un si chuyn thnh Tl2O3. - Cc hidroxit tan d dng trong dung dch axit to thnh mui: In(OH)3 + 3 H3O+ [In(H2O)6]3+ - Tr Tl(OH)3, chng cng tan trong dung dch kim ging nh nhm hidroxit to thnh mui hidroxigalat v hidroxiindat c thnh phn v tnh cht tng t aluminat: In(OH)3 + OH- [In(OH)4]- Ring Ga(OH)3 cn tan c trong dung dch NH3 m c, iu ny chng t tnh axit ca Ga(OH)3 mnh hn nhm hidroxit. - Tt c cc M(OH)3 u c iu ch bng cch cho mui M(III) tc dng vi dung dch kim 4.4.4.3. Mui M(III) - a s mui ca axit mnh d tan trong nc nhng b thy phn kh mnh ging nh mui nhm lm cho dung dch c mt trng axit. Trong nhng mui tan ca axit yu, nhiu mui b thy phn hon ton.41

- Cc halogen MX3 ni chung ging mui AlCl3. Chng tng i d nng chy, d tan trong nc v mt s dung mi hu c. Ging vi AlCl3, cc mui khan GaCl3 v InCl3 bc khi mnh trong khng kh. Chng d dng kt hp vi M'X to thnh nhng phc cht kiu M'3[MX6] v M'[EX4] vi M' l kim loi kim. Chng hn: GaCl3 + 3KCl K3[GaCl6] 4.4.5. Cc hp cht ca Tl c mc oxi ha +1 Ion Tl+ c bn knh 1,44 , tng ng vi bn knh ca cc ion K+, Rb+, Ag+ nn hp cht ca chng ging vi nhiu hp cht kim loi kim v bc. 4.4.5.1. Tl2O - L cht b mu en, nng chy 300C thnh cht lng mu vng tng tc mnh vi thy tinh. N ht m v tan d dng trong nc to Tl(I) hidroxit: Tl2O + H2O TlOH - N cng tan d dng trong ru v axit. Khi un nng trong O2 hay trong khng kh n bin thnh Tl2O3: Tl2O + O2 Tl2O3 - N d b hidro hay CO kh n kim loi. 4.4.5.2. TlOH - L cht dng tinh th mu vng, khng bn v mt nc 100C to thnh Tl2O. N hp th kh CO2 v tan trong nc thnh dung dch kim mnh. Dung dch ca n cng hp th kh CO2, tc dng vi thy tinh v s. Tuy nhin TlOH l baz yu hn KOH. - TlOH c th iu ch bng cch ha tan Tl2O vo nc hoc cho mui Tl2SO4 tc dng vi Ba(OH)2: Tl2SO4 + Ba(OH)2 Tl(OH) + BaSO4

42

CHNG 5. CC NGUYN T NHM IVA (C, Si, Ge, Sn, Pb)5.1. C IM CHUNG c im nguyn t ca cc nguyn t nhm IVA Nguyn t S th t Khi lng nguyn t Bn knh nguyn t () Bn knh cng ha tr () Bn knh ion M2+ () Bn knh ion M4+ () NL ion ha (kcal/mol) I1 I2 I3 I4 C 6 12,01 0,77 259,6 562,2 1104 1487 Si 14 28,08 1,34 1,17 0,34 187,9 376,8 771,7 1041 Ge 32 72,59 1,39 1,22 0,65 0,44 182 367,4 789 1050 Sn 50 118,69 1,58 1,40 1,02 0,67 169,3 337,4 703,2 939,1 Pb 82 207,19 1,75 1,26 0,76 171 346,6 736,4 975,9

Nguyn t ca cc nguyn t ny c lp eclectron ha tr l ns2np2. Do tng nng lng ion ha kh ln, chng khng th mt 4 eclectron ha tr to nn ion 4+, mt khc m in cng khng ln kt hp thm eclectron bin thnh ion 4-. t c cu hnh eclectron bn, nhng nguyn t ca nguyn t nhm IVA to nn nhng cp eclectron chung ca lin kt cng ha tr v trong cc hp cht chng c mc oxi ha t -4 n +2 v +4. 5.2. CACBON 5.2.1. n cht 5.2.1.1. Tnh cht vt l Cacbon thin nhin l mt hn hp ca hai ng v 12C (98,89%) v 13C (1,11%). Ngoi ra trong cacbon cn c lng vt ca ng v phng x 14C. ng v 14 C c trong kh quyn dng kh CO2 vi nng khng i. Nh c chu k bn hy kh ln (5570 nm) cho nn 14C trong kh CO2 ca kh quyn c pht hin trong mi cht c cha cabon nm cn bng vi CO2 ca kh quyn. Khi sinh vt cht n thi ng ha nhng lng mi 14C v lng 14C gim xung do s phn hy phng x. Nh vy bit 14C trong mt vt c ngun gc hu c (tnh c khi cn c vo phng x) v bit hng s nng 14C trong kh quyn, ngi ta c th tnh c thi im m sinh vt cht. Phng php ny cho php xc nh tui ca cc ng vt v thc vt thi c xa vi sai s khong 5%. Cacbon c 3 dng th hnh c trng l kim cng, than ch (graphit) v cacbin, ng vi cc trng thi lai ha c trng ca cacbon. - Kim cng:43

Kim cng c cu trc mng li lp phng, trong tinh th mi nguyn t cacbon trng thi lai ha sp3 lin kt cng ha tr vi 4 nguyn t C bao quanh kiu hnh t din u, khong cch gia cc nguyn t cacbon l 1,545 . Mng li tinh th kim cng l kiu mng li nguyn t in hnh. Ton b tinh th c cu trc rt u n cho nn thc t tinh th l mt phn t khng l. Do vy, kim cng nh c t khi ln (3,51) v cng nht trong tt c cc cht, khng dn in. Tinh th kim cng hon ton trong sut, khng mu v c ch s khc x ln nht nn trng lp lnh. Thang cng ca Mosh 1. tan 6. Phenspat - Than ch: Than ch c cu trc lp, trong mi nguyn t cacbon trng thi lai ha sp2 lin kt vi 3 nguyn t cacbon xung quanh cng nm trong mt lp to thnh vng 6 cnh, nhng vng ny lin kt vi nhau to thnh mt lp v tn. Sau khi to thnh lin kt, mi nguyn t cacbon cn c 1 eclectron trn obital nguyn t 2p cha lai ha s to thnh lin kt vi mt trong 3 nguyn t C bao quanh. Nn lin kt trong than ch khng nh ch trong ton b tinh th. Nh than ch khc vi kim cng: c mu xm, c nh kim, dn nhit v dn in (c dng lm in cc). Than ch tng i mm, d tch thnh lp, v mt ha hc hot ng mnh hn kim cng mt t, khi lng ring d = 2,2. - Cacbin: Cacbin l bt mu en, cha 99% cacbon, c cu trc mng li lc phng, c cu trc mch thng (=C=C=)n, trong mi nguyn t cacbon to thnh 2 lin kt v 2 lin kt . Cacbin l cht bn dn, n c tng hp cch y khng lu. - Cacbon v nh hnh: Nhiu dng v nh hnh ca cacbon nh than g, mui than, than cc... thc t l cc dng vi tinh th ca than ch. Than dng bt mn c b mt tip xc rt ln nn hp ph c mt lng ln kh v dung mi t dung dch. Than mi iu ch c kh nng hp ph rt cao gi l than hot tnh. Li dng tnh cht ny ngi ta dng than hot tnh tr cht c (dng trong mt n phng c), loi cht bn khi lc ng v lc du thc vt. 5.2.1.2. Tnh cht ho hc - nhit thng C kh tr v mt ha hc nhng nhit cao C tr nn hot ng. nhit cao n c th tng tc vi nhiu khng kim li v kim loi, C v nh hnh hot ng mnh nht. - Khi chy trong khng kh C tng tc vi oxi theo phn ng: C + O2 CO2 H = - 94,32 kcal/mol Ngoi kh CO2, trong sn phm lun c mt lng kh CO. Khi nhit cng cao, lng kh CO cng ln: CO2 + C 2CO H = +41,3 kcal/mol44

2. Thch cao 7. Thch anh

3. Canxit 8. Topaz

4. Florit 9. Corunum

5. Apatit 10. Kim cng

Thc t di 500C sn phm t chy C ch l CO2, v trn 900oC ch c CO. V vy ngi ta cho rng trong phn ng chy ca cacbon trong khng kh cn c phn ng ph: 2C + O2 2CO C + 2S CS2 H = - 53,04 kcal H = +26 kcal - Hi lu hunh tng tc vi C to ra cacbon disunfua: - C phn ng vi H2 nhit cao khi c mt xc tc Ni: C + 2H2 CH4 - C tng tc vi nhiu kim loi to thnh cc hp cht cacbua kim loi: Ca + 2C CaC2 4Al + 3C Al4C3 - Khi tc dng vi cc hp cht, C th hin tnh kh. nhit cao n kh c nc, clorat, nitrat, axit HNO3, axit H2SO4 c... to nn kh CO2: C + H2O CO + H2 (Kh than t) C + 2H2O CO2 + 2H2 2C + 4NaNO3 4NaNO2 + 2CO2 C + 4HNO3() CO2 + 4NO2 + 2H2O C + 2H2SO4() CO2 + 2SO2 + 2H2O 2KClO3 + 3C 2KCl + 3CO2 - c bit, C kh c oxit ca nhiu kim loi nhit cao, trong luyn kim ngi ta dng phn ng ny iu ch mt s kim loi: C + CuO Cu + CO Fe2O3 + 3C 2Fe + 3CO - c bit, cu trc lp v xp ca than ch cho php nhiu phn t i vo khong khng gian gia cc lp tinh th to nn vi than ch nhng hp cht kiu xm nhp. V d: Khi tng tc vi flo 450C, than ch to nn mt sn phm mu trng gi l florua than ch vi t l C:F = 1:0,99. Trong trng hp l tng, hp cht ny c cng thc (CF)n, trong mi nguyn t C to nn mt lin kt C-F v 3 lin kt C-C. y C chuyn t trng thi lai ha sp2 sang trng thi sp3. V vy cc lin kt C-C trong tinh th (CF)n khng cn nm trong mt mt phng nh trong tinh th ca than ch v khng cn lin kt khng nh c nn florua than ch l cht cch in. Florua than ch khng tan trong cc dung mi thng thng. Khi un nng trn 500C n phn hy mnh (c th gy n) to thnh cc florua d bay hi ca cc cacbon nh CF4, C2F6, v than mui. Florua than ch rt bn v mt ha hc, n khng tng tc vi axit v vi kim. 5.2.1.3. Trng thi thin nhin Trong thin nhin, C chim 0,14% tng s nguyn t, khng nhiu lm nhng c vai tr c bit ln v hp cht ca cacbon l c s ca mi sinh vt. Mt lng rt ln cacbon nm trong khong vt canxit (CaCO3), dolomit (CaCO3.MgCO3), than m,45

du m. Cacbon cn c trong cc hp cht hu c, chnh than m v du m l sn phm phn hy ca cc hp cht hu c trong iu kin thiu khng kh. Than m hay cn gi l than gm c nhiu loi: - Than antraxit: l loi than gi nht v a cht. N cha trn 90% cacbon c mu t en n xm. - Than : l loi than tr hn antraxit, n cha t 75 n 90% cacbon. Ngi ta chia than ra lm nhiu loi: than bo (hay than m), than gy, than dnh... Than cng c mu en nhng khc antraxit ch trng n c v bo, khi chy cho nhiu khi v t nhit hn than antraxit. Khi c nhit phn, than tch ra mt s cht d bay hi v li than cc. - Than nu: l loi than tr hn nhiu, n cha t 60 n 70% C, c mu nu, mm hn than v antraxit. Nhn vo than nu ngi ta cn nhn thy cu to ca g. - Than bn: l loi than tr nht trong cc loi than m, n cha t 55 n 60% C. N l vt liu mu hung, xp v cha mt lng ln nc. Thnh phn nguyn t ca than bn rt gn vi thnh phn nguyn t ca g. 5.2.1.4. Phng php iu ch cc dng th hnh ca cacbon - Kim cng: Khai thc cc m c cha kim cng trong t nhin. Kim cng nhn to c iu ch bng cch nung than ch nhit 1800 3800C di p sut 60000 120000 atm khi c cc kim loi chuyn tip (Fe, Cr, Ni...) lm cht xc tc: Graphit60000 - 120000atm, xt KLCT 1800 - 3800C

Kim cng

Kim cng nhn to v phm cht k thut khng nhng t m cn vt kim cng thin nhin. Tuy nhin kim cng nhn to c tinh th nh, mu khng p, khng th dng lm trang sc c. - Than ch: iu ch bng cch un nng than antraxit hay than cc nhit 25003000C trong l in c bit. 5.2.2. Cc hp cht ca cacbon 5.2.2.1. Cacbua kim loi Cacbua kim loi l hp cht ca cacbon vi kim loi to thnh khi hai nguyn t tng tc trc tip vi nhau nhit trn 2000C hay khi than tng tc vi oxit kim loi hoc kim loi tng tc vi hidro cacbon nhit cao. Cacbua kim loi c chia lm 2 loi: a. Cacbua ion Cacbua ion c to nn ch yu bi cc kim loi thuc cc nhm IA, IIA, IIIA. Nhng cacbua ny thng l cc hp cht ion nn c gi l cacbua ion. Tinh th ca chng khng c mu, trong sut, khng dn in nhit thng, d b nc v axit long phn hy. Da vo sn phm c to nn khi b phn hy ngi ta chia ra cc nhm sau y: - Cacbua to nn metan khi b thy phn:46

Nhm ny bao gm Be2C, Al4C3. Chng l cht dng tinh th v kh nng chy, trong tinh th ca chng c cation kim loi v anion C4-. Khi tng tc vi nc anion C4- b thy phn gii phng metan, v vy nhm cacbua ny gi l metanit: Al4C3 + 12H2O 4Al(OH)3 + 3CH4 - Nhm cacbua to nn axetilen khi b thy phn: Nhm ny bao gm nhng cacbua c cng thc chung l M2C2 (M l kim loi kim, Au, Ag, Cu), MC2 (M l kim loi kim th, Zn, Cd) v M2(C2)3 (vi M l Al, Fe). Trong tinh th ca nhng cacbua nhm ny c cha ion C22-, khi tng tc vi nc, ion C22- b thy phn gii phng axetilen: CaC2 + 2H2O Ca(OH)2 + C2H2 V vy nhm cacbua ny c gi l axetilen. Cu2C2 v Ag2C2 khng b thy phn nhng phn ng vi axit clohidric cho axetilen. - Nhm cacbua to nn axetilen v hidro cacbon khc khi b thy phn: Nhm ny bao gm YC2, LaC2, TbC2, YbC2, LuC2, Ce2C3, Tb2C3. Trong cc hp cht c cng thc MC2 ngi ta ch yu tm thy kim loi ha tr 3, trong cc hp cht M2C3 kim loi cng trng thi ha tr 3. Nhng cacbua ny khng th coi mt cch n gin l c cha ion C 2 v nguyn t kim loi vi s oxi ha bnh thng. 2 Khi b thy phn chng ch cho 50-70% C2H2 cng vi C2H4, CH4, H2 c l theo phn ng: 2 C23- + 6 H2O C2H2 + C2H4 + OHv nhng phn ng khc na. b. Cacbua xm nhp c to nn ch yu bi cc kim loi chuyn tip, nhng cacbua xm nhp in hnh c cng thc chung l MC (M l Ti, Zn, Hf, V, Nb, Ta) v M2C ( M l Mo, W). Trong tinh th nhng cacbua xm nhp in hnh , cc nguyn t cacbon xm nhp vo nhng l trng bt din ca kim loi, n khng lm bin i kin trc eclectron t do v nhng c tnh khc ca kim loi tinh khit m cn lm bn thm mng li tinh th ca kim loi. Do kin trc nh vy, cacbua xm nhp c nhng c im nh: c nh kim, dn in, rt cng v kh nng chy. cng cacbua xm nhp t 9 10, nhit si (3000 4000oC) cn cao hn nhng kim loi kh nng chy nh Be, W v hn c C. Cc cacbua xm nhp in hnh cn rt bn v mt ha hc, chng ch b phn hy khi un nng vi hn hp HF v HNO3. Chng hn: 3WC + 9HNO3 + 18HF 3H[WF6] + 3CO2 + 9NO + 12H2O Trong s cc cacbua quan trng nht l canxi cacbua. Cacbua canxi (CaC2 ) + CaC2 tinh khit l cht dng tinh th khng mu thuc h lp phng, t khi d = 2,22, nng chy 2300C. Canxi cacbua k thut l khi mu xm thng gi l t n. + Canxi cacbua tng tc mnh vi nc gii phng C2H2: CaC2 + 2H2O Ca(OH)2 + C2H247

+ Khi un nng CaC2 c th tc dng vi H2, N2, S, P. V d: n kt hp vi N2 to ra canxi xianamit: CaC2 + N2 CaCN2 + C + Khi un nng n c th kh c oxit v clorua ca cc kim loi: MgO + CaC2 Mg + CaO + 2C1440 o C

+ Vi nhng tnh cht ha hc nh trn, canxi cacbua c dng sn xut axetilen, canxi xianamit v dng lm cht kh trong luyn kim. + CaC2 tinh khit c iu ch t cc nguyn t nhit cao trong kh quyn Ar: Ca + 2C CaC2 trong k thut: CaO + 3C CaC2 + CO 5.2.2.2. Cacbon monoxit (CO) CO c cu hnh electron: (slk)2 (*s*)2 (xlk)2 (y lk)2 (zlk)2. Cacbon monoxit c khi lng phn t, tng s eclectron v cu to phn t ging nit, nn c mt s tnh cht ha l ca n ging vi nit. a. Tnh cht vt l Ging nh nit, CO l cht kh khng mu, khng mi, kh ha lng (nhit si l -191,5C), kh ha rn (nhit nng chy -204C) v t tan trong nc. N rt bn vi nhit, 6000C vn cha phn hy. b. Tnh cht ho hc Ging nh nit, CO km hot ng nhit thng nhng nhit cao kh nng kh tng mnh c l do s bin i cu trc eclectron bn ca phn t. - Tc dng vi O2: khong 700C CO chy trong khng kh cho ngn la mu xanh lam v pht nhiu nhit, v vy n c dng lm nhin liu. 2 CO + O2 2 CO2 Ho = -67,9 kcal/mol - Tc dng vi S: khi t nng, CO b S oxi ha: CO + S COS - Khi chiu sng hoc c xc tc, CO tc dng vi Cl2 to thnh oxoclorua: CO + Cl2 COCl2 Oxoclorua cn gi l photgen, l mt cht c nng hn khng kh c dng lm bom hi ngt trong chin tranh th gii ln th nht. Photgen kh hot ng nn c dng nhiu trong tng hp hu c. - nhit cao CO c th kh c oxit ca mt s kim loi. Chng hn trong l cao: Fe2O3 + 3CO 2Fe + 3CO2 - CO c th kh c I2O5 n I2, phn ng ny c dng nh lng CO trong ha hc phn tch: I2O5 + 5CO I2 + 5CO248> 2000 o C 1000 o C

- Trong dung dch, kh CO c th kh cc mui ca kim loi qu nh vng, platin, n kim loi t do. PdCl2 + H2O + CO Pd + 2HCl + CO2 Nh phn ng ny ngi ta pht hin c nhng vt CO trong hn hp kh. - Nhng tng tc ca CO vi cc cht oxi ha khc trong dung dch thng ch xy ra khi c cht xc tc. V d: n kh c KMnO4 khi c mt Ag bt, kh c K2Cr2O7 khi c mt mui thy ngn. - Kh nng kh ca CO tng ng H2 phn t. thy r hot tnh tng i ca CO v H2, ta so snh cc hng s cn bng di y cc nhit khc nhau. H2 + CO2 CO + H2O Hng s cn bng l:K= C CO .C H O2

Ho = 9,87 kcal

C H .C CO2

2

tC K

700 0,6

800 0,9

830 1

1000 1,7

1200 2,6

1400 3,45

nhit 830C, trong hn hp cn bng c lng CO v H2 nh nhau, ngha l 2 kh c i lc nh nhau i vi oxi, di 830C CO kh mnh hn, trn 830C H2 kh mnh hn. Tuy vy khi tc dng vi H2, CO c th th hin tnh oxi ha to nn cc sn phm khc nhau ty theo cc iu kin khc nhau. V d: 300C, xc tc Ni: CO + 3H2 CH4 + H2O Trong nhng iu kin nhit , p sut thch hp, vi s c mt ca cc cht xc tc nh Fe, Co, Ni, Ru... CO c th b kh to ra cc hidro cacbon nng hn, to nn exng tng hp. nCO + (2n + 1)H2 CnH2n + 2 + nH2O 2nCO + (n + 1)H2 CnH2n + 2 + nCO2 nCO + 2nH2 CnH2n + nH2O 2nCO + nH2 CnH2n + nCO2 350C, 250 atm, vi xc tc ZnO c hot ha bng Cr2O3, CO kt hp vi H2 to ra ru metilic. CO + H2 CH3OH Phn t CO cn ng vai tr phi t trong nhiu phc cht khc nhau. Cc hp cht cacbonyl ca nhng nguyn t d nh Ti(CO)7, Cr(CO)6, Ni(CO)4... l nhng hp cht rt l th v phng din l thuyt v thc t. Cacbonyl l cc hp cht nghch t, do vy khi chng c to thnh th xy ra s ghp i cc eclectron ha tr ca nguyn t d, lin kt trong cacbonyl c to thnh theo c ch cho nhn nh cc obital t do ca nguyn t d v cc cp eclectron t do ca nhng phn t CO. V d: Crom c 6 obital t do kt hp c vi 6 phn t CO.49

- CO kt hp vi cht hmglbin (Hb) trong mu to thnh hp cht bn: Hb + CO HbCO lm cho Hb khng lm c nhim v ti oxi t phi n cc mao qun ca cc c quan ng vt, v th CO l cht kh ht sc c. N li khng c mu v mi nn ht sc nguy him i vi con ngi. - CO khng tc dng vi nc v kim iu kin thng nhng nhit cao v p sut cao tng tc xy ra. Chng hn 200C, p sut 15at, CO tc dng vi kim to ra mui focmiat. CO + NaOH HCOONa (focmiat natri) - Trong PTN, ngi ta iu ch CO bng cch cho H2SO4 m c vo axit HCOOH lng v un nng: HCOOH CO + H2O H 2 SO 4 d

3d

4s

4p

hoc cho HCOOH tc dng vi axit closunfonic nhit thng. HCOOH + HSO3Cl H2SO4 + HCl + CO - Trong cng nghip kh CO c sn xut lng ln lm nhin liu dng: Kh than t: hn hp CO, H2 (cho hi nc i qua than t nng ) Kh l ga: 25% CO, 70% N2, 4% CO2 (t chy than antraxit trong l ga) 5.2.2.3. Cacbon dioxit (CO2) v axit cacbonic (H2CO3) CO2 c cu to: O=C=O, vi di lin kt C-O l 1,162 . Nng lng trung bnh ca lin kt l 192 Kcal/mol. CO2 l cht kh khng mu, khng mi v v hi chua, nng hn khng kh, d ha lng v d ha rn (tnc = -57C 5 atm). 60 atm, ngay nhit thng n bin thnh cht lng khng mu linh ng. Khi c lm lnh t ngt, cht lng bin thnh khi rn nh tuyt gi l tuyt cacbonic. Tuyt cacbonic khng nng chy di p sut thng m thng hoa -78C. CO2 rt bn vi nhit, 1500C ch mi phn hy thnh CO v O2 vi t l 1,5% v 2000C vi t l 75%. 2CO2 2CO + O2 Ho = 135,8 kcal Kh CO2 khng chy v khng duy tr s chy, khng duy tr s sng, v vy ngi ta dng kh CO2 hay CO2 lng cha chy. Tuy nhin, mt s kim loi hot ng mnh nh K, Mg, Al, Zn vn chy c trong CO2: 4Al + 3CO2 2Al2O3 + 3C Kh CO2 tan c trong nc (1 lt H2O ha tan c 1,7 lt CO2). Khi tan trong nc phn ln CO2 dng hidrat ha, mt lng nh tc dng vi nc to axit cacbonic. CO2(k) + H2O CO2.H2O(dd) H2CO3 Nh vy CO2 l anhidrit ca axit cacbonic nn dc gi l kh cacbonic.50

H2CO3 l mt axit yu khng bn, khng th tch ra iu kin thng. Trong nc n phn ly theo 2 nc: H2CO3 + H2O H3O+ + HCO3HCO3- + H2O H3O+ + CO32K1 = 4,16.10-7 K2 = 4,84.10-11

- iu kin thng CO2 kt hp c vi NH3 kh to amoni cacbamat: ONH4 CO2 + 2NH3 O = C NH2amoni cacbamat

Mui ny khng bn, khi un 180C, P = 200 atm mt nc to ra ur: ONH4 O=C NH2 CO2 cn tc dng c vi cc hp cht baz. CO2 + CaO CaCO3 2KOH + CO2 K2CO3 + H2O 2KNH2 + CO2 K2CN2 + H2O Trong PTN, kh CO2 c iu ch: CaCO3 + 2HCl CaCl2 + H2O + CO2 5.2.2.4. Cacbonat (CO32-), bicacbonat (HCO3-) Axit cacbonic to nn hai loi mui: cacbonat (mui trung tnh) v bicacbonat (mui axit). Anion CO32- c cu to tam gic u tng t phn t BF3. Ion HCO3- v CO32- khng mu nn cc mui cacbonat v bicacbonat ca cation khng c mu u khng mu. Cc mui cacbonat kim loi kim v amoni tan, cc mui cacbonat kim loi khc khng tan, mui bicacbonat d tan hn nhng khng bn nhit, d b phn hy. Ca(HCO3)2 CaCO3 + H2O + CO2 5.2.2.5. Cacbon isunfua (CS2) Cacbon to vi S cc hp cht CS, CS2 (tng t CO, CO2) quan trng nht l cacbon isunfua CS2. trng thi lng CS2 c cu to: S=C=S dC-S = 1,56 - iu kin thng CS2 l mt cht lng khng mu, d bay hi (nhit nng chy l -111C, si 46,2C) c mi thm d chu, rt c, c dng lm thuc tr su. - Trong khng kh, hi CS2 d bc chy khi tip xc vi vt nng:51

NH2 O=C NH2 + H2O

CS2 + 3 O2 CO2 + 2SO2 - nhit thng, n khng tc dng vi nc, nhng 150C b thy phn: CS2 + 2 H2O CO2 + 2H2S ging nh CO2 d chuyn thnh CO32-, CS2 d kt hp vi S2- to ion tiocacbonat CS32CaS + CS2 CaCS3(canxi tiocacbonat )

CS2 cn tc dng vi halogen nh Cl2: CS2 + 3Cl2 CCl4 + S2Cl2 Trong cng nghip, CS2 c iu ch bng cch cho hi S qua than cc nhit 900 -1000C: C + 2S CS2 5.2.2.6. Xian (hay xianogen) trng thi kh, xian gm nhng phn t kp (CN)2 c cu to thng: :NC-CN: dC-C = 1,37; dC-N = 1,13 Xian l mt cht kh khng mu, mi xc, d ha lng v ha rn (ha lng 20,7C, ha rn -34,4C). Xian bn nhit, trn 1000C mi b phn hy to ra CN: (CN)2 2CN Cc gc CN cng rt bn vi nhit, di tc dng ca tia t ngoi hoc khi un nng gn 500C, CN trng hp to thnh mt khi rn v nh hnh mu en khng tan trong nc c thnh phn (CN)n c gi l paraxian, c cu to dng mch vng cha no. Trong khng kh, xian d bc chy cho ngn la mu hng. (CN)2 + O2 2CO + N2 Khi lu trong nc n b thy phn: (CN)2 + H2O HCN + HCNO (HCN: axit xianhidric, HCNO: axit xianic) S thy phn ca xian cng cho thy s ging nhau gia xian v halogen, nht l trong mi trng kim. (CN)2 + NaOH NaCN + NaOCN + H2O V vy CN cn c gi l halogen gi. Xian c iu ch bng cch un nng hn hp gm 2 mui Hg(CN)2 v HgCl2 400C: Hg(CN)2 + HgCl2 Hg2Cl2 + (CN)2 hoc trn dung dch CuSO4 vi NaCN: 2CuSO4 + 4NaCN 2Na2SO4 + 2CuCN + (CN)2

52

5.2.2.7. Hidro xianua v xianua hidro xianua HCN l hp cht cng ha tr H-CN: H-NC Trong hidro xianua bnh thng c c hai dng ng phn nm cn bng vi nhau HCN HNC iu kin thng dng HCN chim 99,5%, khi un nng dng HNC tng ln. hin nay cha tch c HNC tinh khit. HCN l mt cht lng khng mu, c mi kh chu v ht sc c, d ha rn v d bay hi (ha rn -15C, si 25,6C), tan nhiu trong nc, ru, ete theo bt k t l no, trong dung dch nc. HCN l mt axit rt yu (K = 2,1.10-9), yu hn c axit cacbonic. Trong dung dch HCN, b thy phn: HCN + 2H2O HCOONH4 trng thi khan hay trng thi dung dch, HCN bn khi c axit v c lm cht n nh. Nu khng n s trng hp thnh nhng sn phm rn mu en v i khi c th gy n. - Khi c t nng trong khng kh: 4HCN + 5O2 2H2O + 4CO2 + 2N2 HCN c dng trong tng hp cht hu c. N c iu ch theo phn ng: CO + NH3 HCN + H2O Trong PTN: NaCN + H2SO4 NaHSO4 + HCN Mui ca axit HCN gi l xianua cha ion CN- c cu to: [:C N:]nhng phn ng ca ion CN- ging cc phn ng ca ion X-, v d to kt ta AgCN (TAgCN = 1.10-5) ging nh AgCl; ion CN- khng mu nn cc mui xianua khng mu. Do c s eclectron bng s electron ca phn t CO, c cp electron t do C, ion CN- cng to nn cc phc cht bn vi cc ion kim loi chuyn tip KCN + Fe(CN)3 K3[Fe(CN)6] KCN + Fe(CN)2 K4[Fe(CN)6] Cng nh HCN, mui CN ht sc c. Tt c mui CN- u kt ta, tr xianua kim loi kim v kim loi kim th. Ring Hg(CN)2 tan nhiu trong nc v hu nh khng b ion ha. Cc xianua b thy phn mnh: KCN + H2O KOH + HCN53-

dC-H = 1,05 dC-N = 1,15

mt dng phn t khc ng phn vi n l hidro iso xianua HNC c cu to:

500 o C , ThO 2

Cc mui rn KCN, NaCN trong khng kh b thy phn chm bng kh CO2 KCN + CO2 + H2O HCN + KHCO3 Nhiu mui xianua kim loi nng khng tan trong nc nhng tan trong dung dch xianua kim loi kim to phc cht: Mn(CN)2 + 4KCN K4[Mn(CN)6] CN c tnh kh, khi un nng trong khng kh th b oxi ca khng kh oxi ha: 2NaCN + O2 2NaCNO Natri xianat Khi un si, dung dch xianua s kt hp vi S to thnh tio xianat: KCN + S KCNSKali tioxianat-

Trong cc mui xianua th ch KCN v NaCN c dng nhiu vo vic khai thc vng, nh to vi vng mt phc cht tan cho php tch vng ra khi qung. 4Au + O2 + 8NaCN + 2H2O 4Na[Au(CN)2] + 4NaOH 2Na[Au(CN)2] + Zn Na2[Zn(CN)4] + 2Au Phng php thng dng iu ch mui xianua l dng C kh cacbonat khi un nng. Na2CO3 + C + 2NH3 2NaCN + 3H2O Na2CO3 + C + CaCN2 CaCO3 + 2NaCN 5.2.2.8. Axit xianic v axit tioxianic Axit xianic HNCO l mt cht lng d bay hi (ts = 24C, tnc = -84C), tan trong nc to dung dch axit, nhng trong dung dch long axit d b thy phn: HCNO + H2O CO2 + NH3 sau axit kt hp vi NH3 to ra ur: NH3 + HCNO CO(NH2)2 Trong dung dch m c, ax