điện hóa hóa keo

7/30/2019 in ha ha keo

1/64

IN HA HC

1. Phn ng oxy ha kh2. Cn bng phn ng oxy ha Kh

3. Th in cc

4. Nguyn t Gavani5. S in phn

6. nh lut Faraday1


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1.Phn ng oxy ha kh v cp oxi ha kh1.Phn ng oxy ha kh v cp oxi ha kh lin hplin hp

1.1 Phn ng oxy ha kh

PH N NG TRAO I ELECTRON

Nh ng e =

s oxy ha

Nh n e =

S kh

S

oxyha

Skh(soxyha

gi m)

S oxyha (s

oxyha

t ng)


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Phn ng oxy ha khPhn ng oxy ha kh

Phn ng oxy ha kh

PH N NG TRAO I ELECTRON

M t s thu t ng thng d ng:

S oxy ha nh ng

electron t ng s oxy ha S kh nh n electron

gi m s oxy ha

Ch t oxy ha nh n electron

Ch t kh nh ng electron


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Phn ng oxy ha khPhn ng oxy ha kh

Phn ng oxy ha kh


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1.2 Cn bng phn ngCu (s) + Ag+(aq) Cu2+(aq) + Ag (s)

Bc 3: Cu Cu2+ + 2e

2 Ag+ + 2 e 2 Ag

Bc 4:Cu (s) + 2 Ag+ (aq) Cu2+ (aq) + 2Ag (s)

Bc 1: Xc nh bn phn ng oxi ha v kh: OX: Cu Cu2+ + 2e RED: Ag+ + e Ag

B c 2:Cn bng cc bn phng trnh


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1.3 in cc1.3 in cc

in cc: l mt h gm mt thanh dn in ( kim loi

hoc phi kim nh than ch) tip xc vi dung dchcha mt cp oxi ha kh lin hp.

V d:Khi nhng

mt thanh dn in

vo dd cht in lyta c mt in

cc


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Cc loi in cc ph binCc loi in cc ph bin

- in cc kim lai ion kim loi (in cc tan)

- in cc kh ion

- in cc kim loi anion mui khng tan

- in cc tr


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3.1 in cc kim lai ion kim lai (in cc tan)3.1 in cc kim lai ion kim lai (in cc tan)

Gm mt kim laitip xc vi ion can trong dung dch

in cc thng c k

hiu tt M ( r) | Mn+ (dd)

V d: in cc ng

Cu (r) | Cu2+

Qu trnh xy ra Cu -2e Cu2+


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3.2 in cc kh ion3.2 in cc kh ion

Cht kh tip xc vi cation ca n

H+ (dd) | H2(k) | Pt (r)

Qu trnh xy ra

2H+ (dd)+ 2e H2(k)

Nu p sut kh H2 bng 1

atm, a H+=1M, nhit 250

C tac in cc tiu chun hydro(E=0)


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3.3 in cc kim lai anion mui khng tan ca kloi3.3 in cc kim lai anion mui khng tan ca kloi

Kim loi tip xc

vi mui khng tanca n ng thitip xc vi dung

dch cha mui tancng anion.

AgI (r ) + 1e Ag (r) + I- (dd)I

-

(dd) | AgI(r ) |Ag (r )


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3.4. in cc tr3.4. in cc tr

Gm mt thanh kim loi tr (nh Pt) tip xc vi hai dd cht c trng

thi oxy ha kh khc nhau ( v d dd cha hn hp 2 mui Fe2+, Fe3+)

Fe3+,Fe2+(dd)|Pt(r )

Fe2+ - 1e Fe3+


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4. Pin in (Nguyn t Ganvani)4. Pin in (Nguyn t Ganvani)

L mt h gm 2 in cc ghp ni vi nhau thnh mt mch kn


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(-) Zn(s) | Zn2+(aq) || Cu2+(aq) | Cu(s) (+) Ecell = 1.103 V


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Cch biu din nguyn t Ganvani

Anot l in cc xy ra qu trnh oxi haZn (r ) - 2e Zn2+

Catot l in cc xy ra qu trnh kh

Cu2+ + 2e Cu

Cch biu din nguyn t Ganvani

Dng k hiu | ch s phn cch gia hai pha; cc chttrong cng mt pha dng du phy (, );dng | | ch

cu mui; anot c vit bn tri, catot c vit bnphi

(-) Zn(r) | Zn2+ (dd) || Cu2+(dd) | Cu(r) (+)


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5. Th in cc5. Th in cc

5.1 Th in cc tiu chun

Th in cc tiu chun ca mt cp oxy ho -kh l scin ng ca mt pin to bi in cc chun ca cp oxy

ho - kh vi in cc hidro chun


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Th in cc tiu chun

Th in cc hydro tiu chun c biu thPt(r)| H2 (k, 1atm)| H+ (1M) khi l anot

H+ (1M) | H2 (k, 1atm)| Pt(r) khi l catot

E02H+/H2= 0

Hin nay ngi ta thng dng in cc calomen lmin cc so snh thay cho in cc hydro.in cc nych to t kim loi thy ngn trn calomen Hg2Cl2 trong

dung dch KCl Hg2Cl2 (r ) + 1e Hg ( l) + Cl- (dd)

So vi in cc tiu chun hydro th in cc chunca in cc calomen bng + 0, 2680V


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Bng th in cc tiu chun 25Bng th in cc tiu chun 2500CCBng th in cc tiu chun 25Bng th in cc tiu chun 2500CC

Oxihay

u

O

xih

amnh

Bn phn ng khKhh

ayu

Khh

am

nh


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5.2 ngha ca th in cc kh tiu chun

1) So snh mnh cc cht oxy ho v mnh cc cht kh.

Th in cc kh cng ln th tnh oxi ha ca dng oxiha cng mnh, tnh kh ca dng lin hp cng yu

V d:

Fe3+ + e Fe2+ E0 = + 0,71VCu2+ + 2e Cu0 E0 = + 0,337V

Tnh oxi ha ca Fe3+ mnh hn Cu2+, tnh kh ca ca

ng kim loi ln hn tnh kh ca Fe2+


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V d: Tnh s sinh ra bi pin c phn ng :

Ag++ Cr2+Ag(r ) + Cr3+

gi thit hot cc ion 1M

Gii : anot: Cr2+ - 1e Cr3+ E0 = + 0,41V

catot Ag+ + 1e Ag E0 = + 0,80V

Ag++ Cr2+Ag(r ) + Cr3+ E0 = +1,21V

Hay: E0 = + 0,80 (- 0,41) = + 1,21

E = Th kh ca in cc dng - th kh ca in cc m

= E(+) E(-) = Echt oh Echtkh

2) Tnh c sc in ng ca mt pin


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3. D on kh nng din bin ca mt phn ngoxy ho kh

V d: Phn ng sau c xy ra khng nu tt c cccht k chun: Fe3+ + Cu Fe2+ +Cu2+

Gii Fe3+

+ 1e

Fe2+

E0

= +0,771 V

Cu - 2e Cu2+ E0 = -0,337 V

2Fe3+ + Cu 2 Fe2+ + Cu2+ E0 = +0,434V

V phn ng c E0

dng nn phn ng t xy ra

Dng oxi ha ca cp c th in cc kh lnhn c kh nng nhn electron ca dng kh ca cp

c th kh nh hn


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6. Phng trnh Nernst

Trong :

E0: Th in cc tiu chun

n: S e trao i

Q: Biu thc nh lut tc dng khi lng

S ph thuc ca th in cc cng nh sc in ng ca mt pin

c th hin bng phng trnh Nernst

E = E0-0,0592

nlg Q


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C phn ng a A + b B = eE + gG Nu xy ra trong dd long , ta c h thc

G = G0 +RTln = G0 +RTln Q

Mt khc ta c G = -nFEDo ta c th suy ra : nFE = nFE0 - RT lnQ

nhit thng E = E0 (0,0592 /n) lg QTrong

2,303.R.T/F = (2,303 x 8,314 x 298)/96500= 0,0592v n l s e tham gia phn ng

CeECgG

CAaCBb


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V d:

Pt|Fe2+(0.10 M),Fe3+(0.20 M)||Ag+(1.0 M)|Ag(s)

p dng phng trnh Nernst tnh Ecell.


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V d:

Ecell =Ecell - lg Qn

0.0592

Pt|Fe2+(0.10 M),Fe3+(0.20 M)||Ag+(1.0 M)|Ag(s)

Ecell =Ecell - lg

n

0.0592 [Fe3+][Fe2+] [Ag+]

Fe2+(aq) + Ag+(aq) Fe3+(aq) + Ag(s)

Ecell = 0.029 V 0.018 V = 0.011 V

Thay vo: E0 = 0,800-0,771= 0,029V

N h k t t t


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Neu phan ng co ket tua tao rahay co moi trng phan ng thphai tnh lai E0 cua cac cap oxi hoa

kh.V du1: Xet chieu phan ng:

2Cu2+ + 4I- 2CuI + I2

Biet:

120

/210;54,0

2

=+= CuIII

TVE

VECuCu

17,00/2

+=++

Va nong o cac dang 1M

HD: Qua trnh oxi hoa :

I2

+ 2e 2I-

Qua trnh kh:Cu2+ + I- + 1e CuI

2

20

2/2/ ][

][lg

2

059,0

22

+=

I

IEE

IIII

]][lg[059,0 2'0/,/, 22

++=

++ICuEE

CuIICuCuIICu


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Tnh E0Cu2+, I-/CuI :

Cu2+ + 1e Cu+ va TCuI =[Cu+][I-]

V

TEE

CuI

CuCuCuIICu

878,010

1lg059,017,0

1lg059,0

12

0

/

'0

/, 22

=+=

+=

+++

VEEEIICuIICu 338,054,0878,0

0

2/

0

/,

0

22

===+

][

][

lg059,0

20

/ /22 +

+

+=++

++

Cu

CuEE

CuCuCuCu

CuI

CuCuT

ICuE

]][[lg059,0

20

/2

+

+= ++

]][lg[059,01lg059,0 20 /2+++= ++ ICu

TE

CuI

CuCu

V d 2 X t hi h


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HD: AsO43- + 2e + 2H+AsO33- + H2O

[ ][ ][ ]

+

+= 33

2340

//lg

2

059,033

34

33

34 AsO

HAsOEE

AsOAsOAsOAsO

Neu pH=0 => [H+] = 1M va [cac dang]

= 1M 0// 33

34

33

34

=AsOAsOAsOAsO

EE

= 0,57 0,54 = 0,03 > 0 (chieu thuan)

V du 2: Xet chieu phan ng:

AsO43- + 2I- + 2H+ AsO33- + I2 + H2O

pH = 0 va pH = 8 ? Biet :

VE

VE

II

AsOAsO

54,0

57,0

0

2/

0

/

2

3

3

3

4

+=

+=

Va nong o cac dang bang 1M

N H 8 [H ] 10 M [


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Neu pH = 8 => [H+] = 10-8M va [cacdang] = 1M

VEEAsOAsOAsOAsO 098,0)10lg(2

059,0 280// 33343334

=+=

E = 0,098 0,54 = -0,442 < 0

Phan ng theo chieu nghch

AsO3

3- + I2

+ H2O AsO43- + 2I- + 2H+


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Hang so can bang cua phanng oxi hoa-kh

059,0

)(

059,0

.

lg

000

khoxhEEnnE

K

=

=

n: so e trao oi

V du: Tnh hang so can bang va chobiet chieu cua phan ng:

2Fe3 Cu0 Cu2 2Fe2

58,14059,0

)34,077,0(2059,0

)(lg00

===khoxh EEnK

K = 10-14,58 chieu nghch


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1.0 M

Zn+2

e- e

-

Anode Cathode

Zn Cu

1.0 M

Cu+2

7. S in phn v nh lut Faraday


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7.1 nh ngha in phn

in phn l qu trnh oxi ha- kh xy ra trncc in cc khi c dng in 1 chiu i qua chtin ly trng thi nng chy hoc dung dch

Lu : Theo qui c in cc, c qt oxiha (nhng e) l anot, cn in cc m ti xy ra qt kh (nhn e) l catot

+ Trong pin anot l cc m, catot l cc dng

+ Trong in phn catot l cc m, anot l ccdng


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7.2. Th phn gii-Qu th

1) Th phn gii: Th hiu ti thiu ca dng in mt chiu tvo hai in cc ca bnh in phn gy nn s in phn

Th phn gii ca mt cht in ly bng th phn gii ca cationv th phn gii ca anion, tc l bng sc in ng ca pintng ng

V d Th phn gii ca dd CuCl2 v ZnCl2 trong dd 1M l

Dd CuCl2: E0=E02Cl-/Cl2- E0Cu2+/Cu= 1,36-(+0,34) = 1,02V

Dd ZnCl2: E0=E02Cl-/Cl2- E0 Zn2+/Zn= 1,36-(-0,76)= 2,12V


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2.Qu th

Qu th l hin tng khi t vo in cc mthiu in th bng th in cc nhng khng xyra qu trnh in phn m cn mt hiu in thcao hn

V d nh cc ion Fe2+, H+, Ni2+, Co2+


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7.2 nh lut Faraday nh lut 1:Khi lng cht thot ra t l vi in lng qua bnh

in phn m= kQTrong k l ng lng in ha v gi tr n bng khi

lng cht thot ra in cc khi c mt n v in lng i quabnh in phn

Q l in lng c th tnh bng n v Faraday (F),

1F= 96.500 C = 26,8 A.h nh lut 2: Nhng in lng nh nhau i qua bnh in phn

lm thot ra cng mt s ng lng gam chtC 1 F in lng i qua bnh in phn thot ra 1 ng lng

gam cht bt kThay Q=I.t v = A/n th biu thc ton hc ca nh lut lm= (A.I.t)/(n.F)

Al n.t.g; I cng dng in (Ampe); t l thi gian(giy),

F= 96500 C


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1.0 M

Zn+2

e- e-

AnodeCathode

Pin

>1.10V

Zn Cu

1.0 M

Cu+2

Q = It


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Mt s ngun in ha thng dngMt s ngun in ha thng dng

Pin

Acqui

S in phn


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Pin


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Acqui


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Acqui ch gm hai tm ch khot nhiu l cha PbO nhng trongdung dch H2SO4 nng 25% 30% , lc ny xy ra phn ng:PbO + H2SO4 = PbSO4 + H2O

Khi np in (sc):Cc (+) : PbSO4 - 2e- + 2H2O = PbO2 + SO42- + 4H+

Cc (-) : PbSO4 + 2e- = Pb + SO42-Nh th trong c acqui xy ra phn ng:

2PbSO4 + 2H2O = Pb + PbO2 + 2H2SO4v PbSO4 cc m bin thnh ch hot ng, cc dng binthnh PbO2. Khi acqui hot ng s xy ra qu trnh phng in:

Cc (-) : Pb - 2e- + SO42- PbSO4Cc (+) : PbO2 + 2e- + 4H+ + SO42- PbSO4 + 2H2O

Nh th trong c acqui xy ra phn ng:Pb + PbO2 + 2H2SO4 = 2PbSO4 + 2H2O


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. Mt s ngun in ha thng dng. Mt s ngun in ha thng dng

S in phn


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HA KEO

N i dung: - Dung d ch keo - C u t o h t keo

- Tnh ch t c a dung d ch keo - S ong t c a h t keo - ng d ng c a dung d ch keo


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1. Dung dch keo

- Dung dch co pha phan tanco kch thc t 10 7-10 9mc goi la dung dch keo.

- Cac hat cua pha phan tan cgoi la hat keo.

- Do kch thc cua pha phan tanrat nho nen hien tng be mattrong dung dch keo ong vai troquan trong.

Cac loai he keo


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48

Cac loai he keo:

Kh dung (kh + long hay ran, VD:

sng, khoi),Bot (long+ kh,VD: bot xa phong),

Nhu tng (long+ long, VD: sa),Huyen phu (long+ ran, VD: sn),

Bot ran (Ran+ kh, VD: mop xop),

Huyen phu ran (ran+ long, VD:b)

- Chung ta ch khao sat he keo co


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49

Keo a longla keo hap thu cacphan t cua moi trng phantan. Cac hat keo a long c baoboc bang mot lp vo solvat. Khimoi trng phan tan la nc thgoi la keo a nc.

Keo k longla keo hau nh khonghap thu cac phan t cua moitrng phan tan. Khi moi trnghan tan la nc th oi la keo k

Phn loi:


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Muoi cua acid beo co au knc la day hirocacbon va aua nc la au cha nhom phan

cc (VD: nhom OH, NH, COO)Trong nc cac phan t co haiau a nc va k nc sap xep

sao cho cac au k nc chum laivi nhau tao thanh phan t khonglo. au a nc quay ra ngoai e


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2. Cau tao cua hat keo

- Xet mot hat keo sat (III) hydroxid.Khi thuy phan FeCl3 trong ncnong tao thanh ket tua Fe(OH)3

theo phng trnh phan ng: FeCl3 + 3H2O Fe(OH)3+3HCl

- Sat (III) hydroxid nam di dangnhng hat rat mn tao thanhnhan keo:

mFe(OH)3 [Fe(OH)3]m


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S o cau tao cua mixen cua keo

sat (III) hydroxid


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- Be mat nhan keo hap phu cac ionFe3+ co trong dung dch tao thanhlp ion b hap phu:

[Fe(OH)3]

m+ nFe3+

[Fe(OH)3]m.nFe3+

- Cac ion Fe3+ nam tren be mat

nhan keo se hut cac ion Cl

tch ienam lai gan tao thanh lp oi ionb hap phu:

[Fe(OH)3

]m

.nFe3+ + xCl3+ (3n-x)+

T b h t k l t h i d


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Toan bo hat keo luc nay tch ien dng(3n-x). Mot phan cac oi ion Cl khac cach xa nhan hn tao thanh lp oi ionkhuyech tan. Tat ca cac hp phannay tao thanh mixen:

{[Fe(OH)3]m.nFe3+.xCl}(3n-x)+ (3n-x)Cl-

nhan lp ion lp oi lpoi ion

keo b hap ion b

khuyech tanphu hap phu

hat keomixen


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Tnh bn vng:

- Do s tch ien cung dau cuacac hat keo. - oi vi keo a nc, do lp vo

hydrat quyet nh. Lp vo naykhong cho cac hat keo ket tu laivi nhau.

- Do chuyen ong nhiet hon loancua cac hat keo, song yeu to nayla th yeu.

3. Tnh chat cua dung


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3. Tnh chat cua dungdch keo

Hieu ng Tyndall: - Chieu mot chum tia sang manhqua mot bnh ng dung dch keothay mot hnh non sang rat ro.

-Nguyn nhn: do hat keo co kch thc nho, khi tia

sang cham vao hat keo th hat keose tan xa tia sang theo moi phng. Luc nay moi hat keo tr thanh

mot iem sang. Do o ta co the


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- Cac tnh chat: o giam ap suat

hi bao hoa, o tang nhiet o soi,o giam nhiet o hoa ran, apsuat tham thau, cua dung dch

keo the hien yeu hn so vi dungdch that. Do vi nong o mol bang nhau

th so tieu phan co trong mot nv the tch cua dung dch that baogi cung ln hn nhieu so vi dungdch keo.

T nh hoat ong be mat


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T nh hoat ong be matcua hat keo :

- Cac tieu phan tren be mat ch

b hut bi cac tieu phan bentrong hat keo.

- Tao nen sc cang be mat

- He keo co dien tch be mat lnnen co sc cang be mat ln.

- Quyet nh tnh bam dnh cua cac

loai keo dan, tnh tay ra cua xaphong va chat tay ra, ien tchcua hat keo va nhieu tnh chat

khac. 4. S ong tu keo


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4. S ong tu keo Qua trnh ong tu keo x y ra khi:

- Lam giam hay trung hoa c ientch cua cac hat keo k nc - Ho c pha v lp vo hydrat cua

cac hat keo a nc- Loai keo k nc khi ong tu sekhong keo nc theo nen ket tua

di dang bot rat mn hoac dangbong.

- Loai keo a nc khi ong tu sekeo theo mot lng nc tng oi

ong tu keo bang chat


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ong tu keo bang chatien ly

- Khi cho mot chat ien ly vao dungdch keo th hat keo se hap phuthem cac ion ngc dau nen ientch cua hat keo giam nhanh lam cho

keo ong tu. - Cac keo a nc co lp vo hydrat

ben vng nen muon ong tu phai

s dung mot lng chat ien ly lnhn nhieu so vi trng hp keo knc.

ong tu keo bang keo tch


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ong tu keo bang keo tchien trai dau

- Khi tron lan hai dung dch keo tch

ien trai dau th cac keo tch ientrai dau se trung hoa lan nhau vaket tu xuong.

- V du: e ket tua cac hat keo attrong nc song tch ien am, khithem phen nhom KAl(SO4)2.12H2O th

Al3+ trong phen thuy phan tao thanhkeo mang ien tch d ng trung hoavi keo am cua at nen chung

ong tu xuong. ong tu keo bang cach


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- Mot so chat keo khi un nongse b ong tu do khi nhiet otang th s hap phu ion giam, doo lam giam ien tch cua hat

keo.

ong tu keo bang cachun nong

ng dung cua cac dung


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ng dung cua cac dungdch keo

- Cac ng dung cua dung dch keorat rong rai cung nh s phong phuva a dang cua chnh cac dung dchkeo.

- Hau het cac thc pham va cactieu phan cua c the chung ta(chat beo, protit, hydratcarbon,) la

cac chat keo. - Khoi, sng mu, khong kh b o

nhiem, nuc t nhien, nc thai

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