1

MC LCLI CM N......................................................................................................... MC LC................................................................................................................1 M U...................................................................................................................4 1. L do chn ti..................................................................................................4 2. Mc tiu v nhim v nghin cu ti.............................................................4 3. Cc phng php nghin cu..............................................................................4 4. i tng v khch th ca ti nghin cu....................................................5 5. Gi thuyt khoa hc............................................................................................5 6. Lch s ti nghin cu....................................................................................5 7. Gii hn ti nghin cu..................................................................................5 NI DUNG ..............................................................................................................6 CHNG 1: TNG QUAN1.1

S lc v nguyn t st................................................................................. Tnh cht vt l v tnh cht ha hc..................................................6 Trng thi thin nhin v phng php iu ch...............................9 Mt s ng dng ca st.....................................................................10 S to phc ca st vi thuc th hu c..................................................11 Kh nng to phc ca Fe3+ vi thuc th axit sunfosalixilic..........11 Kh nng to phc ca Fe vi cc thuc th khc...........................11 . Thuc th SCN-...................................................................................11 .Thuc th o phenantrolin.................................................................13 .Thuc th bato phenantrolin............................................................13 .Thuc th 1 (2pyridylazo) 2naphthol (PAN)..............................14 . Thuc th 4 (2pyridylazo) rezocxin (PAR)...................................14 .Thuc th trioxyazobenzen (TOAB)...................................................15

1.1.1 V tr v cu to ca st...................................................................................6 1.1.2 1.1.3 1.1.4 1.2 1.2.1 1.2.2 1.2.2.1 1.2.2.2 1.2.2.3 1.2.2.4 1.2.2.5 1.2.2.6

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1.3 1.3.1 1.3.2 1.4 1.4.1 1.4.2 1.4.3 1.4.4 1.5 1.5.1 1.5.2 1.6 1.6.1 1.6.2 1.6.3 1.7

Nghin cu v thuc th axit sunfosalixilic................................................16 Tnh cht ca thuc th axit sunfosalixilic........................................16 Kh nng to phc ca axit sunfosalixilic.........................................17 Cc phng php xc nh st.....................................................................17 Phng php khi lng....................................................................17 Phng php trc quang.....................................................................17 Phng php chun oxi ho kh..................................................18 Cc phng php khc xc nh st..................................................19 Cc phng php xc nh thnh phn phc............................................19 Phng php h ng phn t gam...................................................19 Phng php t s mol........................................................................19 Cc phng php xc nh h s hp th phn t ca phc...................19 Phng php h ng phn t gam...................................................19 Phng php x l thng k ng chun........................................20 Phng php Komar...........................................................................20 nh gi cc kt qu phn tch....................................................................21

CHNG 2: K THUT THC NGHIM 2.1 Dng c v thit b.........................................................................................22 2.2 Ha cht v cch pha ...................................................................................22 2.3 Cch tin hnh...............................................................................................23 2.4 Phng php nghin cu..............................................................................23 CHNG 3: KT QU V THO LUN 3.1 Kho st ph hp th ca phc...................................................................24 3.2 Kho st pH ti u v nh hng ca pH n s to phc.....................26 3.3 Kho st s nh hng ca thi gian n s to phc.............................27 3.4 Xc nh thnh phn phc...........................................................................29 3.4.1. Xc nh thnh phn phc khong pH th nht................................29

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3.4.2. Xc nh thnh phn phc khong pH th hai.................................33 KT LUN..............................................................................................................38 Ti liu tham kho..................................................................................................39

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M U1. L do chn ti Trong cng ngh Ha hc th ha hc phn tch khng nh c vai tr ca mnh qua vic s dng cc phng php ha hc, vt l, ha l khi nghin cu thnh phn ca cht. Mt trong nhng phng php t c nhng thnh tu to ln trong khoa hc nghin cu l phng php trc quang khi xc nh hm lng ca cc nguyn t, cc cht v hp cht. Vi nhng thnh tu t c t phng php trc quang m ra nhng c hi mi cho vic nghin cu, i su hn tm hiu v ng dng ca phng php ny trong thc tin, tm ra cc yu t nh hng,. V vy m ti chn ti: Nghin cu nh hng ca pH n s to phc ca Fe3+ vi axit sunfosalixilic (SSal) lm bi kha lun tt nghip . 2. 2.1 Mc tiu v nhim v nghin cu ti .Mc tiu:

- Bit c vai tr ca phng php trc quang trong ha hc phn tch. - Xc nh thnh phn ca phc st (III) vi axit sunfosalixilic bng phng php trc quang. - Vn dng phng php ny trong vic nghin cu nh hng ca pH n s to phc ca Fe3+ vi axit sunfosalixilic (SSal) 2.2 .Nhim v: ti cn thc hin cc nhim v trng tm sau: - Nghin cu phng php trc quang trong ha hc phn tch. - Nghin cu nh hng ca pH n s to phc ca Fe3+ vi axit sunfosalixilic (SSal) 3. Cc phng php nghin cu + Nghin cu l lun: nghin cu cc ti liu, cc trang web, bi vit,.c lin quan + Nghin cu thc nghim:

5

- Tm hiu nguyn l hot ng ca my o mt quang + Nghin cu ton hc: v biu , th, phng php ly gi tr trung bnh, cng thc ton hc thng k,. 4.4.1

i tng v khch th ca ti nghin cu .i tng: i tng nghin cu ca ti l nh hng ca pH .Khch th: Gi thuyt khoa hc ti nghin cu nh hng ca pH n s to phc ca Fe 3+ vi axit sunfosalixilic (

4.2 5.

S to phc ca Fe3+ v axit sunfosalixilic (SSal )

Fe(III) - SSal) bng phng php trc quang. Nu ti nghin cu thnh cng, c th p dng cho vic xc nh hm lng Fe trong rau mung v mt s cht khc. 6. Lch s ti nghin cu ti ny c nghin cu nhng ch dng li ch xc nh thnh phn phc ca Fe(III) - SSal bng phng php trc quang. Ti chn ti ny tip tc nghin cu v nh hng ca pH n s to phc ca Fe3+ vi axit sunfosalixilic ( Fe(III) SSal ) v tm ra mt s h s thch hp. 7.-

Gii hn ti nghin cu ti c thc hin trong phm vi: Nghin cu phng php trc quang trong ho hc phn tch. Nghin cu nh hng ca pH n s to phc ca Fe(III) SSal.

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NI DUNG

CHNG 1: TNG QUAN1.1 .S lc v nguyn t st 1.1.1

V tr v cu to ca st

St l mt nguyn t kim loi ph bin (sau nhm), ng th t v hm lng tri t, chim 1,5% khi lng v tri t. K hiu : Fe S th t: 26 NTK : 55,847 Cu hnh electron: 1s22s22p63s23p63d64s2 St th 26 , thuc chu k 4 v phn nhm ph VIIIB1.1.2

Tnh cht vt l v tnh cht ha hc

1.1.2.1. Tnh cht vt l: St l kim loi mu trng xm, d rn, d dt mng v gia cng c hc. St c tnh dn in, dn nhit tt. Di 8000C st c tnh nhim t, b nam chm ht v tr thnh nam chm (tm thi). St c 4 dng th hnh ( dng , , , ) bn nhng khong nhit nht nh: Fe () 700 Fe () 911 Fe () 1390 Fe () 1538 Fe lng C C C C Nhng dng v c kin trc tinh th kiu lp phng tm khi nhng c kin trc electron khc nhau nn Fe () c tnh st t v Fe () c tnh thun t, Fe () khc vi Fe () l khng ha tan C. Dng Fe () c cu trc tinh th lp phng tm din, dng Fe () c cu trc lp phng tm khi nh dng v nhng tn ti n nhit nng chy.0 0 0 0

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Cc hng s vt l quan trng ca st: dn tos (oC) tonc (oC) 1536 I1 7,9 I2 16,18 BKNT (Ao) 1,26 I3 30,63 m in 1,83 I4 56* KLR cng in(Hg=1) 10 2880 Nng lng ion ha: Mc nng lng ion ha Nng lng ion (g/cm3) (thang Mox) 7,91 4-5 I5 79* I6 103

ha (eV) * Gi tr cha tin cy. 1.1.2.2. Tnh cht ha hc: St l kim loi c hot tnh ha hc trung bnh. iu kin thng nu khng c hi m, chng khng tc dng r rt vi nhng nguyn t khng kim loi in hnh nh O2 , S , Cl2 , Br2 v c mng oxit bo v. Nhng khi un nng, phn ng xy ra mnh lit, nht l khi kim loi trng thi chia nh. Khi un nng trong khng kh kh, st to nn Fe2O3 v nhit cao hn, to nn Fe3O4: 3Fe + 2O2 c mng bo v:t 0

Fe3O4

Kh Cl2 phn ng rt d dng vi st to thnh FeCl3 l cht d bay hi nn khng to 2Fe + 3Cl2 2FeCl3 St tc dng trc tip vi kh CO to thnh cacbonyl kim loi. St tinh khit bn trong khng kh v nc. Ngc li, st c cha tp cht b n mn di tc dng ca hi m, kh cacbonic v oxi trong khng kh to nn g st: 4 Fe + 3O2 2Fe3O4 do lp g st xp v gin nn khng bo v st trnh b oxi ha tip. St phn ng vi nc: nhit nng , st phn ng vi hi nc:C Fe + H2O 570 FeO + H2 570 C 3Fe + 4H2O Fe3O4 + 4H20 O

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St to thnh hai dy hp cht Fe2+ v Fe3+. Mui Fe2+ c to thnh khi ha tan st trong dung dch axit long tr axit HNO3. Mui ca Fe2+ vi axit mnh nh: HCl, H2SO4, d tan trong nc, cn mui ca cc axit yu nh: FeS, FeCO3, kh tan. Khi tan trong nc, mui st dng [Fe(H2O)6]2+ mu lc nht. Mu lc ca [Fe(H2O)6]2+ rt yu nn thc t dung dch ca mui Fe2+ khng c mu. Mui FeSO4 l cht tinh th mu trng, d ht m v d tan trong nc. Khi kt tinh t dung dch nc nhit thng, thu c tinh th hidrat FeSO4.7H2O. Tinh th FeSO4.7H2O c mu lc nht, nng chy nhit 640C, d tan trong nc v ru. Khi un nng tinh th FeSO4.7H2O mt dn nc v tr thnh mui khan FeSO4. nhit cao hn (>5800C) mui khan b phn hu thnh oxit: FeSO4 580 Fe2O3 + SO3 + SO2 C Quan trng vi thc t nht l (NH4)Fe(SO4)2.6H2O, c gi l mui Mohr. Tinh th mui Mohr c mu lc, d kt tinh, khng ht m v bn vi oxi khng kh nn c dng pha dung dch chun Fe2+ trong ho hc phn tch. Fe(OH)3 bn trong khng kh, khng tan trong nc v trong dung dch NH3. Fe(OH)3 tan d dng trong axit to thnh dung dch mui Fe3+. a s mui Fe3+ d tan trong nc, cho dung dch cha ion bt din [Fe(H2O)6]3+ mu tm nht. Khi kt tinh t dung dch nc, mui Fe3+ thng dng tinh th hidrat nh: FeCl3.6H2O, Fe(NO3)3.9H2O mu nu vng, phn st (NH4)Fe(SO4).12H2O mu tm nht Mui Fe3+ b thu phn mnh nn dung dch c mu vng nu. Ch trong dung dch c phn ng axit mnh (pH 12 Ba z Phn hy pH > 12 phc b phn hy do xy ra s hnh thnh phc hidroxo.1.2.2 1.2.2.1

Kh nng to phc ca Fe vi cc thuc th khc .Thuc th thioxianat (SCN-)

Thioxianat l mt thuc th nhy i vi Fe3+, c dng nh tnh v nh lng hm lng st. V axit thioxianat l mt axit mnh nn nng SCN- t b nh hng bi pH trong dung dch. Cng mu ca Fe3+ SCN- hp th cc i bc sng = 480 nm, dung dch phc Fe3+ SCN- b gim mu khi ngoi nh sng, tc gim mu chm trong vng axit yu v nhanh khi nhit tng. Khi c mt H2O2 hoc

12

(NH4)S2O8 cng lm cho cng mu v bn mu ca phc gim i. Khi nng SCN- ln khng nhng n lm tng nhy ca php o m cn loi tr c nh hng ca cc ion F-, PO43- v mt s anion khc to phc c vi ion Fe3+. Trong mi trng axit c nhng ion gy nh hng n vic xc nh Fe3+

bng SCN- nh C2O4 ,

F- . Ngoi ra cn c cc ion to phc mu hay kt ta vi ion thioxianat nh Cu2+, Co2+, Ag+, Hg2+, S cn tr ca Co2+ l do mu ca bn thn n ta c th loi tr bng cch o mt quang bc sng thch hp. Cc ion Hg2+, Cd2+, Zn2+ to phc vi SCN- s lm gim cng mu ca Fe3+ - SCN- . Do mun s dng phng php ny cn phi tch cc ion nh hng n mu ca phc. Phng php dng thuc th SCN- c gii hn pht hin km, chnh xc thp m c s dng rng v phng php ny n gin, nhanh, p dng c trong cc dung dch axit mnh v chi ph ca n tng i thp. Phng php ny xc nh c hm lng st t 1 10 ppm. Ngi ta cng s dng phc ca Fe 3+ vi SCN- chit ln dung mi hu c nhm tng chn lc v nhy cho php xc nh Fe2+. Trong nghin cu ny cc tc gi nghin cu thnh cng php chit Fe2+ - SCN- bng cht chit tetrabutyl amoni sunfat (TBAS) bng dung mi clorofom. SCN- l mt trong s t cc thuc th v c c dng xc nh st. Cng da trn cc c s cc nghin cu trc v s to phc mu ca Fe v SCN-, gn y mt s tc gi xut mt s phng php xc nh st tng v Fe 3+ trong nc ma nng c ppb. y l phng php xc nh st n gin, c nhy v chn lc cao. Phng php ny da trn phn ng to mu gia Fe3+ v SCN- v s c mt ca mt cation mang hot tnh hot ng b mt, chng hn nh cetyl pyridin clorua (CPC), trong mi trng axit HCl c, sau chit phc ny vi N octyl axetamin bng dung mi toluen hoc clorofom. H s hp th phn t ca phc l = 2,6.105 l.mol-1.cm-1 ti bc sng cc i l max = 480 nm v h s lm giu l 10. Gii hn pht hin l 5.106 mg/ml. Cc ion thng i cng vi st khng gy cn tr ti php xc nh. Phng php ny c kim tra bng phng php quang ph hunh

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quang hp th nguyn t (GF AAS) v s dng xc nh hm lng st nng c ppb trong cc mu nc.1.2.2.2

.Thuc th o Phenantrolin

Thuc th o Phenantrolin l mt thuc th kh nhy, dng xc nh ion Fe 2+ da trn s to phc gia thuc th v Fe2+ .N N

Fe2+

N N

Fe2+/3

Phc ny hon ton bn, cng mu khng thay i trong khong pH t 2 9 v phc c max = 510 nm. Mt s nguyn t nh hng n qu trnh ny nh: bc, st do to nn kt ta; Cd, Hg v Zn to phc kh tan vi thuc th ng thi lm gim cng mu ca phc st ; Be , Sn, Cu, Mo cng gy nh hng v cc nguyn t ny c th hn ch nh hng bng cch iu chnh pH trong khong hp nh : Hg c th c mt 10 ppm (pH t 3 9), Be c th c khong 50 ppm (pH t 3 5,5), Co c khong 10 ppm (pH t 2 - 5), Sn2+ khng qu 20 ppm (pH t 2 3), Sn4+ nh hn 50 ppm (pH = 2,5) u khng cn tr s to mu ca phc gia st v thuc th. Fe3+ cng to phc vi o Phenantrolin, phc ny c mu xanh lc nht c cc i hp th max = 360 nm .1.2.2.3

max =

585 nm. Tuy vy, phc ny khng bn theo thi gian v chuyn dn sang mu vng nht .Thuc th bato phenantrolin

Phc ca Fe2+ vi bato phenantrolin c th c chit bng nhiu dung mi hu c, trong tt nht l ancol n amylic v iso amylic v clorofom.

N

N

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Ngi ta thng dng clorofom chit v n c t trng cao nn d chit. Phc ny c th c chit bng hn hp clorofom ancol etylic khan vi t l 1:5 hoc 5:1, pH thch hp cho s to phc l 4 7 . trnh hin tng thy phn i vi cc ion ta cho thm vo dung dch mt t mui xitrat hay tactrat. Cu2+ gy nh hng cho vic xc nh Fe2+ bng thuc th bato phenantrolin, ngoi ra mt s ion kim loi ha tr II nh Co, Ni, Zn, Cd vi mt lng ln cng gy nh hng. Cc anion khng gy nh hng cho vic xc nh st bng thuc th ny.1.2.2.4

.Thuc th 1-(2-pyridylazo)-2-naphthol (PAN)

Thuc th to phc vi st c nghin cu trong mi trng kim pH ti u 6 8, phc bn theo thi gian v phc c thnh phn Fe : R l 1 : 2 max = 565 nm , = 2,7.104.N=N N O H2O

FeO N N=N

H2O

1.2.2.5

.Thuc th 4- (2- pyridylazo) rezocxin ( PAR )

Thuc th PAR c cng thc cu to nh sau:N=N N HO OH

PAR l cht bt mu thm, tan tt trong nc, ancol v axton. Khi tan trong nc dung dch c mu vng. Trong thng mi, thuc th PAR thng c s dng di dng mui c cng thc phn t C11H8N3O2Na.H2O.

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Cc cn bng ca thuc th PAR trong dung mi nc:K0=10-3,1 + N H H3R+(pH12 Ba z Phn hy pH c nh hng ln n s to phc ca cc cht, in hnh l nh hng n s to phc ca Fe(III) SSal. Tu theo khong pH no m thnh phn phc c mt t l xc nh. Theo l thuyt, khong pH = 9 11 , ta c thnh phn phc Fe(III) SSal = 1: 3 . Tuy nhin, khi lm thc nghim t l ny khng c xc nh do mt quang qu nh. V thc t cho bit vic xc nh thnh phn phc hai khong pH u c ngha quan trng hn khong pH th ba.

39

TI LIU THAM KHO1. 2.

Hong Nhm. Ho hc v c, Tp 3. NXB Gio dc H Vit Qu - Nguyn Tinh Dung. Cc phng php phn tch ho l.HSP H Ni L Th Yn Kiu. Kho lun Tt nghip. HSP ng Thp, nm 2008 Nguyn Duy i , Nguyn Tinh Dung, Trn Thnh Hu, Trn Quc Sn, Nguyn Vn Trn T Hiu. Phn tch trc quang. H Tng hp H Ni, 1994 A. T. Pilipenko V. Ia. Pochinoc I. P. Xeraa Ph. . Sepchenko

19913. 4.

Tng Mt s vn chn lc ca ha hc Nh xut bn gio dc , 2003.5.

6 A. T. o B. . oo . . Cepea . . eeo