Chuong 6 Mot So Ung Dung Cua Dien Hoa Hoc

8/10/2019 Chuong 6 Mot So Ung Dung Cua Dien Hoa Hoc

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CHNG 6

MT S NG DNG CA

IN HA HC

TRNG I HC SI GNB MN HA L


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NI DUNG BO CO

6.1 Ngun in ha hc

6.2 in phn

6.3 n mn v chng n mn kim loi

NI DUNG CHNG 6


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6.1.1 Pina. Cc loi pin

Pin l ngun in mt chiu c to ra nhnng lng ca cc phn ng ha hc. Pin cng dng rng ri trong k thut v tuyn, thngtin, in t, t ng ha v nhiu lnh vc kinh tquc dn khc.


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6.1.1 Pin

a. Cc loi pin

Pin kh Le clanch- Pin Le clanch thucloi pin mui hay cn gi

l pin acid.- S :

()Zn | NH4Cl | MnO2(r)+ C | C (+)

Hnh 6.1 Pin Le Clanch


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Cc phn ng chnh nh sau:(): ZnZn2++ 2e

(+): 2MnO2+ 2H++ 2eMn2O3.H2O

Do s c mt ca NH3, NH4+v Cl;

chng s phn ng vi Zn2+ to ra cc snphm ph nh ZnMn2O4; ZnCl2; Zn(OH)2;Zn(NH3)2Cl2, cc sn phm ph ny tch t

dn dn quanh cc dng lm cho pin mtdn kh nng hot ng.

Zn + 2NH4++ 2MnO2(r)Zn

2++ NH3+ 2MnO(OH)


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Pin Le clanch l loic s dng rng ri

nht hin nay. VitNam, pin Le clanch

c sn xut di nhn

hiu pin Con Th (Vnin, H Ni), pin Con. in p ca pin khvo khong 1,5V.

V ngoi

Than ch

(cathode)

Zn (anode)

hn hpNH4Cl + ZnCl2

Bt than ch +MnO2 bao quanh

cathode

Hnh 6.2 Pin Le Clanch


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Pin kim ManganCu to: ()Zn, Hg | KOH (dd)| MnO2, C (+)

Phn ng cc in cc:Cc ()

Zn + 4OH+ 2H2O [Zn(OH)4(H2O)2]2+ 2e (i)

[Zn(OH)4(H2O)2]2ZnO + 2OH + 3H2O

Cc (+)

MnO2

+ H2

O + eMnO(OH) + OH

MnO(OH) + H2O + eMn(OH)2+ OH


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Hnh 4.2Pin kim

anode,ZnO phdn ln Znv lm cho

Zn th ng,cn tr phnng (i)tiptc xy ra.


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Pin kim thu ngnAnode lm bng hn hng km - thy

ngn; hn hp HgO v Cacbon dng kem nho

ng vai tr cathode, cn cht in ly l KOH v

ZnO. Cc phn ng ti in cc:Anode: Zn(Hg) + 2OHZnO(r)+ H2O(l)+ 2e

Cathode: HgO(r)+ H2O(l)+ 2eHg (l)+ 2OH

Zn(r) + HgO(r) + H2O + 2OHHg + [Zn(OH)4]

2

in p ca pin thy ngn bng 1,35V.


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i tngs dng ca

pin kimthy ngn


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i tng s dngca pin Liti


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Tn pin i tng s dng u v nhc im

Pin kh

Le clanch

Radio, n pin, chi

R sch, nhiu kch c. Khi lm vic vicngcao, NH3c thlm ngtmtdng.

Tui th thp. C thghp nitipnhiupinkh to pin c in p cao hn. Dunglngpin vo khong0,1 Ah/cm3.

Pin kim

Mangan

Radio, n pin,

chi

Khng b ngt dng. Thi gian hot ng luhn pin Le clanch. Sch, nhiu kch cnhng t hn pin Le clanch.

Pin kim

thu ngn

ng h, my trthnh, my tnh

nh, camera

Kch thc nh, gi thnh cao hn pin kh vthi ra thu ngn c. C in p hi nh hnsong li n nh hn do thnh phn cht in

ly khng thay i trong qu trnh s dng.Dung lng ca pin ny vt xa pin kh: 0,3Ah/cm3.

Pin liti

My tnh, ng h,my ghi hnh, my

tnh xch tay.

Khng c nhng t tin, thi gian s dngngn, c th ti np in nhng in th d

bin i.


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b. AcquyAcquy l ngun in ha hc c kh nng hot

ng lu di nh tnh cht thun nghchca qutrnh phng in v np in ca n.

Acid Kim

Ch Niken - St Bc - Zn Niken - Cadimi

Anode Pb Fe Zn Cd

Cathode Pb, PbO2 C, NiOOH Ag, Ag2O C, NiOOH

Scin ng (V) 2,00 1,36 1,60 1,30

Bng 6.2Cc loi acquy chnh c thng mi ha


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Acquy ch

(cng thng c gi l acquy acid)

Li ch xp

Dung dch

H2SO430%

Li ch phPbO2xp


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Acquy chgm hai tm ch khot nhiu l chaPbO nhng trong dung dch H2SO4nng 25%

30%, lc ny xy ra phn ng:PbO + H2SO4 = PbSO4 + H2O

Khi np in(sc):

(+):PbSO42e-+ 2H2O = PbO2 + SO42-+ 4H+(): PbSO4+ 2e- = Pb + SO42-

Nh th trong c acqui xy ra phn ng:

2PbSO4+ 2H2O = Pb + PbO2+ 2H2SO4

v PbSO4 cc m bin thnh ch hot ng, ccdng bin thnh PbO2.


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Khi acquy hot ng s xy ra qu trnh phngin:

(): Pb 2e-+ SO42- PbSO4(+):PbO2+ 2e

-+ 4H++ SO42-PbSO4+ 2H2O

Nh th trong c acquy xy ra phn ng:

Pb + PbO2+ 2H2SO4 = 2PbSO4+ 2H2O

Acquy ch c pht minh nm 1859 do Gaxton

Plantnh vt l ngi Php (1834 1889).Hin nay, trn mt na lng ch trn th gii sn

xut ra c dng sn xut acquy ch.


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Acquy kim Nicad v niken stPhn ng to dng in nh sau:

2NiOOH + M + 2H2O 2Ni(OH)2+ M(OH)2

Sc in ng khong 1,301,34Vi vi acquy

NiCd v khong 1,371,41Vi vi acquy Ni Fe.

Acquy kim c tui th cao, t n 1 2 nghn chu

k phng np in.

phng in

npin


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Acquy NiAg, vi phn ng:

Ag2O + Zn ZnO + 2Ag

S: 1,601,85Vvi 100 200 chu k lm vic.

Acquy NikenHiro, vi phn ng:

2NiOOH + H2 2Ni(OH)2

S: 1,321,36Vvi vi nghn chu k lm vic.

phng in

npin

phng in

npin


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MT S ACQUY HIN I


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NG DNG

CA ACQUY


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6.1.2 Pin nhin liua. Pin nhin liu hiro - oxi

Anode:

2H2+ 4OH4H2O(L)+ 4e

Cathode:

O2+ 2H2O(L)+ 4e4OH

Tng qut: 2H2+ O2H2O

Sc in ng ca pin:E0= 0Ox+

0Red= 0,83 + 0,40 = 1,23V


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S dng: cung cp in nng v nc tinh

khit trong cc chuyn bay v tr.

u im: Sch, nhiu pin nhin liu hot ng

khng gy nhim mi trng. To ngun innng di ng.

Nhc im: Khc vi cc pin thng thng,

pin nhin liu khng tch tr c in nng, nch hot ng khi dng nhin liu c np vo

lin tc. in cc mau hng v rt t.

a. Pin nhin liu hiro - oxi


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b. Pin nhmkhng khPin nhmkhng kh tng t pin nhin liu

ch cc cht phn ng c np nh k nu khngni l lin tc.

Khi pin hot ng, anode xy ra s oxi ha nhm:x4| Al

(R)+ 4OH

(aq)4[Al(OH)

4]

(aq)+ 3e

cathode xy ra s kh oxi:x3| O2 + 2H2O(L)+ 4e

4OH

Phn ng tng cng:4Al(R)+ 3O2(K)+ 6H2O(L)+ 4OH

(aq)4[Al(OH)4]

(aq)

EPin= 2,7V


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S dng: gim nhim mi trng, ngi

ta phc tho nhng xe hi chy bng in vpin ny c ha hn trong tng lai c th dng

vn hnh loi xe hi gia nh.

u im: Pin nhmkhng kh c t l in

nng/khi lng rt cao. 1 mol electron cn 9

gam Al (MAl= 26,98 g/mol).

Nhc im: cn phi np nh k nc, nhm

v than ch.

b. Pin nhmkhng kh


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c. Mt s pin nhin liu khc

Pin nhin liu kim AFC(Alkaline Fuel Cells)

Pin nhin liu acid phosphoric PAFC

(Phosphoric acid Fuel Cells)

Pin nhin liu mui carbonate nng chyMCFC(Molten Carbonate Fuel Cells)

6 2 S i


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6.2 S in phn

6.2.1nh ngha in phn

in phn l qu trnh oxi ha kh xy ra trncc in cc khi c dng in 1 chiui qua chtin ly trng thi nng chyhoc dung dch.

Lu Theo qui c in cc, c qu trnhoxi ha (nhng e) l anode, cn in cc m ti xy ra qu trnh kh (nhn e) l cathode.

+ Trongpinanode l cc m, catot l cc dng.+ Trong in phncathode l cc m, anode l

cc dng.


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6.2.2 Th phn gii Qu tha. Th phn gii

Th phn gii lth hiu ti thiu ca dngin mt chiu t vo hai in cc ca bnhin phn gy nn s in phn.

Th phn gii ca mt cht in ly bng thphn gii ca cation v th phn gii ca anion,tc lbng sc in ng ca pin tng ng.


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6.2.3 nh lut Faradaynh lut 1

Khi lng cht thot ra t l vi in lng quabnh in phn.

m = k.Q

Trong ,kl ng lng in ha; v gi tr ca n bng

khi lng cht thot ra in cc khi c mt n vin lng i qua bnh in phn.

Ql in lng c th tnh bng n v Faraday (F),1F = 96.500 C = 26,8 A.h


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nh lut 2

Nhng in lng nh nhau i qua bnh inphn lm thot ra cng mt s ng lng gamcht.

C 1F in lng i qua bnh in phn thot ra 1

ng lng gam cht bt k.Thay Q = I.t v = A/n th biu thc ton hc ca

nh lut lm = (A.I.t)/(n.F)

Trong , I cng dng in (Ampe); t l thi gian(giy), F = 96500 Coulomb.

6.2.3 nh lut Faraday


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MT S NG DNG THC TINCA IN PHN

1. in phn sn xut

2. Tch v tinh luyn kim loi bng in phn

3. S dng phc cht trong in phn4. Tng hp cc cht hu c bng phng phpin ha

5. M kim loi6. nh bng in ha

7. Ty du m in ha


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1. in phn sn xut

in phn sn xut nhm

Hnh 4.7Thit b in phn nng chy nhm


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1. in phn sn xut

in phn sn xut NaOH Cl2


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2. Tch v tinh luyn kim loibng in phn

Tinh luyn Zn

Tinh luyn ng


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Luyn Zn thng dng nht l in phn dungdch ZnSO4. Sn phm Zn thu c c th t99,99%.

Phn ng cathode, kt ta Zn:

Zn2++ 2e Zn

Oxi thot ra trn in cc khng tan:2H

2O O

2+ 4H++ 4e

Tinh luyn Zn bng in phn


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Do qu th ca H2trn Zn rt cao nn Zn cth kt ta trong mi trng acid vi hiu sutrt cao. Th kh ca Zn2+m hn in th kh

ca H+

. C mt cc tp cht khc, chng s ktta ng thi vi Zn. Trn cathode, c nhng vtr c qu th hiro thp.



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Qu trnh thot hiro xy ra mnh, ng thivi ha tan Zn c kt ta (theo c ch pincc b). Cc tp cht nh Cu, Bi, Ge v Sbkhng ch lm gim hiu sut dng m cn ngn

khng cho Zn kt ta. V vy mc ch x lqung Zn to ra dung dch km sunfat khngc tp cht nh hng khng tt n phn ng

cathode.



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Tinh luyn ngng sn xut bng cc qu trnh luyn kim cha

nhiu tp cht, thng 0,5 2%. Tp cht nhhng xu n tnh cht c, in ca Cu. 0,15% Phoc 0,5 % As s gim ng k dn in. V vy,

ci thin tnh cht in ca Cu l l do chnh cain phn tinh luyn. L do th hai ca tnh luynin ho l tch cc kim loi qu nh Au, Ag, Pt, PdCc phn ng chnh in cc

Cu2e Cu2+ (anode)

Cu2++ 2e Cu (cathode)


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Cc kim loi tp cht c mt anode ng,nh Fe, Zn cng b oxi ha thnh Fe2+v Zn2+

trong dung dch song chng khng b kh cathode ti th kh ng. Cc kim loi c thdng in hn nh vng, bc khng b oxi haanode v ng li y bnh in phn khianode ng b ha tan. Bng cch ny ng t rng l 99,5%


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h h h b


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4. Tng hp cc cht hu c bngphng php in ha

Phn ng kh nitro benzen bng in ha lmt trong nhng phn ng c ngha quan trngi vi l thuyt v thc nghim. Mc d n

c nghin cu hng chc nm v s cng trnhc cng b lin quan n vn ny l rt ln,nhng c ch ca n cho n nay vn cha xc

nh c mt cch chnh xc v s phc tp caqu trnh.


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Cc giai on trung gian ch yu sau:

Nhng do s khc bit gia cc giai on inha ring v s tng tc ha hc ca cc snphm trung gian vi nhau v vi cht tham gia

phn ng, trn cc cathode khc nhau v trongcc cht in ly khc nhau cc sn phm thuc rt khc nhau (ngoi s k trn cn c

azokcybenzen, ozobenzen, hydrazobenzen,benzidin v n-amin ofenol).

2 2 2

6 5 2 6 5 6 5 6 5 2

E e H eC H NO C H NO C H NHOH C H NH


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5. M kim loia.Lp m bo v

Nhim v ch yu ca lp m ny l bo vkim loi bn khi b n mn trong mi trng sdng.

Lp m bo v khng ch cch ly kim loi nnkhi b tc dng va chm ca mi trng xungquanh m cn c tc dng bo v in ha kim

loi nn. Cn c vo c ch n mn in ha mngi ta chia lp m thnh lp m anode v lpm cathode:


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Lp m anodel lp m m kim loi c inth m hn in th kim loi nn trong mi

trng n mn.Lp m anode ph bin trong thc t: lp m

km, cadimi, thic trn thp.

Lp m cathodel lp m m kim loi m cin th dng in hn in th kim loi nntrong mi trng n mn. Lp m cathode bo

v hiu qu kim loi nn nu l lp m lin tc,khng bong, trc, nt n hoc c l xp.


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b. Lp m trang tr Lp m c mu sc p, bng sng, hp dn

th hiu v gi c v p trong mt thi giandi cho cc thit b, my mc, dng c, trangsc, n trang,

Ngi ta cn to c lp m trang tr bngcch m o mt lp mng kim loi qu him nhvng, rodi, platin, paladi hoc crom. Lp m oca cc kim loi ni trn c mu sc p, bng,

sng gi c v p hp dn trong nhiu mitrng.


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c. Lp m trang tr, bo v Lp m va c tnh bo v c hiu qu kim

loi nn va c tnh trang tr cao. Ch c lp mcathode mi tha mn c cc c tnh trn calp m trang tr bo v. Cc lp m sau ythng ng vai tr lp m trang tr bo v:

- Lp m niken crom.- Lp m ng crom hay ng thau crom.- Lp m ng nikencrom.Trong cc lp m trang tr bo v, lp m

trung gian ng vai tr lp m bo v.


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d. Lp m k thutLp m in c s dng rng ri vi mc ch

k thut, v d:- Lp m lm tng bn chng ma st trc.- Lp m lm phc hi cc trc, cc chi tit b

mi mn.

- Trong cng nghip bn dn (transitor, diot,)ngi ta dng lp m vng m cc tip in, cclinh kin in t,

- To lp m crom vi rnh trong pittong, xylanh thm du, chng ma st.


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6. nh bng in haNhiu kim loi kh nh bng c bit l nhm

v cc loi thp khng g, c th nh bng bngphng php in ha mt cch d dng, hiuqu cao, gi thnh h. C ba nhm kim loithng c nh bng in ha:-Nhm v cc hp kim ca n.- ng v cc loi hp kim ca n.- Cc loi thp.Ch cc hp kim mt pha (dung dch rn) v kimloi nguyn cht mi c th nh bng in ha.


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7. Ty du m in haTrong k thut m kim loi ngi ta cn phi

lm sch du m trn b mt cc chi tit. Phngphp in ha lm sch b mt c tc dng ttnht, c th tin hnh ty du m anode, cathodev ty du hn hp.

Cc phng php ty du m in ha: tydu m cathode; ty du m anode; ty du mhn hp

6 3 h ki l i


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6.3 n mn - chng n mn kim loi6.3.1. n mn kim loi

n mnl hin tng thc t kim loi b bin ithnh cc hp cht ha hc bn vng nhit nghn (oxit, sulfur, carbonate,) di nhng dng

ph hy khc nhau ca nhiu tc nhn trong mitrng.

Khi b n mn, kim loi b h hi v cc tnh cht

ca n (c hc, l hc, ha hc,) b bin i ghgm, do cc gi tr s dng, gi tr cng ngh vc gi tr thm m ca vt liu khng cn na.


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C nhiu loi n mn v phn ln kim loi bh hi do n mn in hamt dng n mnkh ph bin trong t nhin.

n mn in hal qu trnh ph hy kimloi do b tc ng bi mi trng cha cht

in li.C ch n mn in ha l c ch hot ngca mt pin in on mch.

V d in hnh v n mn trong kh quyn ca


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V din hnh v n mn trong kh quyn cast (st b g):

Trn b mt st c nhng vng ng vai tranode, ti y c phn ng oxi ha:

Fe (r) Fe2++ 2e

O2+ 4H+

(aq) + 4e 2H2O(l)

g stkhng kh

O2

Fe2+

Fe3+

nc

cathode anode

Fe Fe2+(aq)+ 2e

Fe2+(aq) Fe3+

(aq)+ 2e

e

Hnh 4.

9

S g ca st


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Cc electron sinh ra trong phn ng oxi ha sts kh oxi trong kh quyn to ra nc ti khu

vc cathode, l nhng vng khc trn b mt st:O2 + 4H

+(aq)+ 4e

2H2O(L)

Phn ng oxi ha kh tng qut l s t hp

hai na phn ng trn:Fe(r)+ O2+ 4H+(aq) 2Fe2++ 2H2O(L)V ng vi sc in ng ca vi pin n mn:

E0

= 1,23(0,44) = 1,67V


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Nhng ion H+mt phn c cung cp bi kh CO2

trong kh quyn ha tan vo nc:

CO2+ H2OH++ HCO3

Ion Fe2+hnh thnh trn hp phn anode ca b mt

tip tc b oxi ca kh quyn oxi ha to ra g st:4Fe2+(aq)+ O2+ (4 + 2x)H2O(l) 2Fe2O3.xH2O+ 8H+(aq)

Dng hirat ca st oxit Fe2O3.xH2Ochnh l gmu nu. Nh vy, iu kin st b n mn l phic oxica kh quynv nc.


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St khng b gtrong khng kh khhoc trong nckhng c oxi ha tan. S n mn khng ch gii hn st.Mt kim loi khc cng d c xu hng b n mn, lnhm.

Mt s kim loi khc dng c tin nh ng, bc

cng b n mn nhng tc n mn rt nh b.Cu (r) Cu2+(aq)+ 2e

Ag (r) Ag+(aq)+ e

Khi tip xc vi kh quyn, ng to ra mt lp CuCO3

mu xanh lc c tc dng bo v. Mt cch tng t nhng n bng bc khi tip xc vi thc phm s to ra mt lpAg2S.

3 /( 1, 66 )

Al Al V

2 /

( 0, 44 )Fe Fe

V

6 3 2 Ch ki l i


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6.3.2 Chng n mn kim loi chng n mn, bin php c tnh nguyn

tc l cch li kim loi vi mi trng xm thc.C nhiu phng php khc nhau, nhng

phng php ny ubt ngun t c trng ph

hy kim loihoc t nhng iu kin s dng

khai thc vt liu kim loi.

Ph h h h


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Phng php che phPhng php ny nhm c

lp b mt kim loi khi mitrng xm thc. Lp ph cth l mt lp sn khng thm

nc.Hp kim ha

Ch to thnh cc hp kim

khng nhng tng cng tnhcht c hc m cn chng nmn, nht l nhit cao.

Ph h i h h


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Phng php in ha hc

Phng php bo v cathode bng in cc

hy sinhPhng php bo v cathode bng dng in

cathode

Phng php bo v anode

X l mi trng n mn


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X l mi trng n mn(bin i mi trng xm thc)

lm gim tnh xm thc ca mi trng, ngita s dng cht c ch n mn (chm n mn).

Tc dng ca c ch:

- Hp ph phn t cht c ch hu c ln b mt.- Th ng ha kim loi.

- To lp kt ta mui ln b mt, ngn oxi c th tip

cn kim loi.- Loi b tc nhn n mn

Ki Mi Cht c ch


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Kim

loi

Mi

trng

Cht c ch

Hu c V c

StAcid

Anilin; Etyl v ietylamin;

Piriin; Quinolin;-naphtoquinolin;

Andehyt formic; Thioiglicol

As2O3; NaAsO2;K2Cr2O7

Tr. tnh Natri benzoat; hirazin Na2SO3

ThpAcid

(nh i vi st)

-

Tr. tnh Natri benzoat -

ngAcid Thiour K2Cr2O7; KMnO4

Tr. tnh - Ca(HCO3)2; CrO42

Nhm

v

Km

Tr. tnh -

Ca(HCO3)2;

Natri v Canxi

hexametaphotphat

Kim Glucose S2 v SiO 2

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Chuong 6 Mot So Ung Dung Cua Dien Hoa Hoc