Giáo Trình Hóa Lý Kỹ Thuật

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TRNG AI HOC A LAT

GIAO TRNH

HOA LYDUNG CHO SINH VIEN NGANH MOI TRNG

TRAN KIM CNG - 2002


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Giao trnh Hoa ly dung cho SV nganh Moi trng - 2 -

Phan I.ONGHOAHOC.CHNG I.MOT SO KHAI NIEM C BAN.

I.Toc o cua phan ng hoa hoc:1.nh ngha:

Toc o cua phan ng hoa hoc la bien thien nong o cua mot chat a cho (chattham gia phan ng hoac san pham phan ng) trong mot n v thi gian.

2.Cac cach bieu dien toc o phan ng:a.Bieu dien toc o phan ng theo nong o cua chat tham gia phan ng :

Xet phan ng : spAA 21 +

thi iem t1, C A1 1, C A1 2,

thi iem t2, C A2 1, C A2 2,

Ta co:( )

vC C

t t

C

t

A A A_

, ,=

=

2 1

2 1

1 1 1

(I-1),

( )v

C C

t t

C

t

A A A_

, ,=

=

2 1

2 1

2 2 2

(I-2).

S d co dau tr ang trc (I-1,2) la v khi t2> t1th C < , cung nh C >k2 th vt >>vn va luc o, ta co thecoi: , co ngha la phan ng c coi la phan ng mot chieu.v v k C Ct A = 1 1. .

2.Phan ng thuan nghch bac 1 (bac 1-1):a.Cac v du:

( ; ABSCNNH4 )CSNH 22b.ong hoc cua phan ng thuan nghch bac 1-1:

Xet phan ng:

k1k2

A B

t = 0 a b

t = t a -x b +x

Ta co: v dx

dtk a xt = =

11 ( ) (II-32) va v

dx

dtk b xn = = +

22 ( ) (II-33), trong o: x1

va x2la phan nong o chat A b mat i do A bien thanh B va phan nong o chat B bmat i do B bien thanh A tng ng.

T 2 phng trnh tren, ta suy ra:

v v v dx dx

dt

dx

dtt n= =

=1 2 xkkbkakxbkxak )()()( 212121 +=+=

++= xkk

bkakkk

21

2121 )( (II-34). ay la phng trnh ong hoc dang vi phan cua

phan ng thuan nghch bac 1-1.

atk a k b

k k

1 2

1 2

+ = , ta co:

dx

dtk k x= + ( )(1 2 ) (II-35). Lay tch phan phng

trnh nay, ta c: k kt x

1 2

1+ =

ln

(II-36). ay la phng trnh ong hoc dang

tch phan cua phan ng thuan nghch bac 1-1.

V k1/k2=K nen ta suy ra: = +Ka bK 1

(II-37).

Thac s Tran Kim Cng Khoa hoa hoc


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Bang thc nghiem, ta se xac nh c: K k

k

b x

a x

cb

cb

= = +

1

2

(II-38) va khi biet

c K, ta se xac nh c . Biet va bang thc nghiem, ta xac nh c x thiiem t, ta se xac nh c k1+k2. Biet k1+k2va k1/k2, ta se xac nh c k1va k2.

VIII.Phan ng song song:1.nh ngha va cac v du:

a.nh ngha:Phan ng song song la phan ng ma t cac chat tham gia phan ng xay ra ong thitheo nhieu hng khac nhau e tao ra cac san pham khac nhau.

b. Cac v du:+ Phan ng nhiet phan kaliclorat:

KClO3

KCl O2

KCl KClO4

+

+

+ Phng trnh phan ng song song dang tong quat:

A + ...B1B2

Bn

+ ...

+ ...

+ ... 2.ong hoc cua phan ng song song mot chieu bac 1:

a.ong hoc cua phan ng song song mot chieu bac 1 n gian nhat:Xet phan ng:

AB

C

k1

k2

t = 0 a 00

t = t a -x x1

x2

v dx

dtk a xA B = =

11( ) ( II-39 ); v

dx

dtk a xA C = =

2

2 ( ) (II-40).

Phng trnh ong hoc dang vi phan cua phan ng song song tren la:



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dx

dt

dx

dt

dx

dtk a x k a x k k a x= + = + = + 1 2 1 2 1 2( ) ( ) ( )( ) (II-41). Lay tch phan

phng trnh tren, ta c: k kt

a

a x1 2

1+ =

ln (II-42). ay la phng trnh ong hoc

dang tch phan cua phan ng song song tren. T phng trnh nay, ta suy ra:

(II-43).a x a e k k t = +. ( 1 2)

T cac phng trnh (II-39,43), ta co: (II-44). Lay tch

phan phng trnh nay, ta c:

dx k a e dtk k1 11 2= +. . .( )

[ ]x ak

k ke

k k t

11

1 2

1 1 2=+

+( ) (II-45).

Tng t, t cac phng trnh (II-40,43), ta cung tm c:

[ ]x ak

k k

e k k t22

1 2

1 1 2=

+

+( ) (II-46).

T cac phng trnh (II-45,46), ta suy ra: (II-47)

va

x x k k 1 2 1 2: = :

x ak

k kt1

1

1 2

, = = + (II-48); x

ak

k kt2

2

1 2

, = = +(II-49).

b.ong hoc cua phan ng song song mot chieu bac 1 dang tong quat:

A

Xn

X1

X2

k1k2

kn

t = 0 a 0

0

M

0

t = t a-x x1

x2

M

xn

Ta co phng trnh ong hoc dang vi phan cua phan ng tren la:

dx

dt

dx

dt

dx

dt

dx

dt

d x

dtk k k a x k a xn

i

i

n

n i

i

n

= + + + = = + + + = ==

1 2 1 1 2

1

L L( )( ) ( ) (II-

50).Lay tch phan phng trnh nay, ta c:



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kt

a

a xi

i

n

= = 1

1ln (II-51) (II-52).=

=a x a e

k tii

n

..

1

Tng t nh muc 2.8.2.a, ta tm c cac bieu thc sau ay (II-53):

x ak

k

e

i

i

n

k tii

n

11

1

1 1=

=

=

.

, x ak

k

e

i

i

n

k tii

n

22

1

1 1=

=

=

.

, va x ak

k

enn

i

i

n

k tii

n

=

=

=

1

1 1.

.

T cac phng trnh tren, ta suy ra: k1: k2: ...: kn=x1:x2:...:xn(II-54).

3.Ghi chu:+ T viec khao sat cac loai phan ng song song khac nhau tren,

ta thay rang ty le nong o cua cac chat san pham trong cac hngkhac nhau cua phan ng song song co gia tr khong oi, khongphu thuoc vao thi gian, mac du hang so toc o phan ng cuachung la khac nhau.

+ oi vi phan ng song song, phan ng rieng re nao dien ra vi toc o ln nhat,phan ng o se quyet nh tnh chat va toc o cua toan bo phan ng song song.

IX.Phan ng noi tiep:1.nh ngha va cac v du:

a.nh ngha:Phan ng noi tiep la phan ng ma t cac chat tham gia phan ng khong bien oi trctiep thanh san pham cuoi cung ma hnh thanh lan lt mot hoac nhieu chat trunggian.

b.Cac v du:+ Phan ng xa phong hoa dietylphtalat bang kiem:

C H COOC H NaOH C H COONa COOC H C H OH

C H COONa COOC H NaOH C H COONa C H OH

6 4 2 5 2 6 4 2 5 2 5

6 4 2 5 6 4 2 2 5

( ) ( )

( ) ( )

+ +

+ +

+ Phng trnh tong quat cua phan ng noi tiep la:

A X Y Ak k k k n+ +L L1 2 3 / L

C

va co the trong giai oan nao o cua phan ng tren la phan ng thuan nghch.

2.ong hoc cua phan ng noi tiep mot chieu bac mot dang n gian nhat:Xet phan ng: A Bk k1 2

t = 0 a 0 0

t = t a -x y = x - z z



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Ta co:

= = dC

dt

dx

dtk a xA 1 ( ) (II-55),

dC

dt

dy

dt

d x z

dt

B = =

=( )

k a x1 ( ) k x z2 ( ) (II-

56)

vadC

dt

dz

dtk x zC = = 2 ( ) (II-57).

Ta can biet rang:

)60II(dt

dz

dt

dy

dt

dxhay)59II(

dt

dC

dt

dC

dt

dC

0dt

dC

dt

dC

dt

dC)58II(aCCC

CBA

CBACBA

+=+=

=++=++

a.Xac nh s phu thuoc cua nong o tng chat A, B va C vao thi gian:+ Tm CA:

T phng trnh (II-55), lay tch phan, ta c: (II-61).C a x a eAk t= = . 1

+ Tm CC = z:

T cac phng trnh (II-57,61),ta suy ra:

dz

dtk x z k a e k zk t= = 2 2 1 1( ) . ( ) 2 (II-62).

Giai phng trnh vi phan tuyen tnh cap mot khong thuan nhat nay, ta c:

C z a k

k ke

k

k keC

k t k t= =

+

1 2

2 1

1

2 1

1 2 (II-63).

+ Tm CB:

T cac phng trnh (II58,61,63),ta suy ra: ( )C y k a

k ke eB

k t k t= =

1

2 1

1 2 (II-

64).b.o th cua phan ng noi tiep:

+ Bieu thc tnh tmax va CB max:

21

21

21

2

1

maxkk

klnkln

kk

k

kln

t

=

= (II-65); =maxBC

12

2

kk

k

2

1

k

ka

(II-66).

+ Bang bien thien:

T 0 t max

C A a 0CAtmax



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CB 0 0C Bmax

CC 0 aCCt max

+ o th cua phan ng noi tiep tren co dang nh H.II.5.

C

t

a

tmax

C C

C

A

B

C

*

M

H.II.5: o th cua phan ng noi tiep bieu dien s phu thuoc cua CA, CBva CCvao t.

c.Chu y:Trong mot day nhng phan ng noi tiep, neu co mot phan ng nao o cham

nhat so vi cac phan ng khac th toc o phan ng o se quyet nh toc o cua toanbo phan ng.



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CHNG III.LY THUYET VE CAC QUA TRNH S CAP.I.Anh hng cua nhiet o en toc o phan ng:

1.Qui tac Vanthoff (Vanhop):Nh chung ta a biet, khi tang nhiet o th toc o phan ng hoa hoc cung tang len;

s tang o, noi chung, la rat ln.

e bieu th s phu thuoc cua toc o phan ng vao nhiet o, Vanhop a a ra quitac gan ung la: Khi tang nhiet o them 10oth toc o phan ng tang t 2 en 4 lan,

tc la = = +k

k

T

T

100 2 4 , trong o la he so nhiet o cua toc o phan ng,

la hang so toc o T o, T+10 o tng ng.

k kT T, +100

Qui tac Vanhop ch la qui tac gan ung va cung ch ap dung c trong motkhoang nhiet o nhat nh; con trong khoang nhiet o ln hoac nhiet o cao, qui tacVanhop khong ap dung c na.

2.Phng trnh Arrhenius (Areniuyt):Bieu thc pho bien va chnh xac hn thng c dung e bieu th anh hng cua

nhiet o en toc o phan ng la phng trnh Areniuyt.

S thiet lap phng trnh Areniuyt la da vao nhiet ong hoc nh sau:

oi vi qua trnh ang tch, ta co: 2V

C

RT

U

T

Kln =

(III-1).

oi vi qua trnh ang ap, ta co:

ln K

T

H

RT

P

P

=

2 (III-2).

Trong o K (KPhoac KC) la hang so can bang cua phan ng va K k

k= 1

2

(III-3) (k1

va k2 la hang so toc o cua phan ng thuan va nghch tng ng), la hieung nhiet ang ap, hieu ng nhiet ang tch tng ng, R la hang so kh, T la nhiet o

tuyet oi.

H U,

Neu coi hieu ng nhiet la hieu cua hai mc nang lng E1va E2th, t cac phng

trnh (III-1,2,3), ta co:d k

dT

d k

dT

E

RT

E

RT

ln ln1 2 12

2

2 = (III-4). T phng trnh (III-4),

ta suy ra:d k

dT

E

RTC

ln 1 12

= + (III-5) vad k

dT

E

RTC

ln 2 22

= + (III-6).

Bang thc nghiem, ngi ta a tm c C trong hai phng trnh tren bang khong

va v vay, cac phng trnh o c viet lai nh sau:d k

dT

E

RT

ln 12

= 1 (III-7) va



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d k

dT

E

RT

ln 22

= 2 (III-8). T cac phng trnh nay, ta co the viet thanh mot phng

trnh dang chung la:d k

dT

E

RT

ln=

2 (III-9).

Phng trnh (III-9) la phng trnh Areniuyt dang th nhat - dang vi phan. Nobieu th s phu thuoc cua hang so toc o k cua phan ng vao nhiet o T.

E co th nguyen cua nang lng va Areniuyt goi no la nang lng hoat hoa. E1goi la nang lng hoat hoa cua phan ng thuan va E2 goi la nang lng hoat hoa cuaphan ng nghch.

Neu lay tch phan phng trnh (III-9), vi s chap nhan E la mot hang so, khongphu thuoc vao nhiet o ( mot khoang nhiet o nhat nh), th ta c:

ln k E

RTB=

+

(III-10). Phng trnh (III-10) cung la phng trnh Areniuyt dangth hai - dang tch phan. T phng trnh (III-10), ta thay rang neu ta bieu dien sphu thuoc cua lnk vao 1/T th ng bieu dien la mot ng thang nh tren H.III.1.

C

O

lnk

1/T

H.III.1: S phu thuoc cua lnk vao 1/T.

T o th H.III.1, ta suy ra c: OCB= va = = E

Rtg E R tg . (III-

11).

Nh vay, bang thc nghiem, ta co the de dang xac nh c nang lng hoat hoacua phan ng.

T phng trnh (III-10), neu ta at B=lnA th ta co:

ln ln .k E

RTA k A e

E

RT=

+ =

(III-12). Phng trnh nay cung la mot dang cua

phng trnh Areniuyt.

T phng trnh (III-12), ta rut ra mot vai nhan xet sau:

+ Neu T = const th:

- Khi E ln th k se be, ngha la toc o phan ng se be. Ngc lai, khi E be th k seln, ngha la toc o phan ng se ln.

ieu o co ngha la nhiet o khong oi, nhng phan ng co nang lng hoat hoaln se xay ra kho khan va cham; neu nang lng hoat hoa qua ln th thc te phan



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ng hoa hoc khong xay ra. Ngc lai, nhng phan ng co nang lng hoat hoa be sexay ra de dang va nhanh.

- Khi E ln, e phan ng co the xay ra, ngha la e co toc o u ln, th phai thc

hien phan ng nhiet o cao.- oi vi nhng phan ng co nang lng hoat hoa bang nhau, phan ng nao c

tien hanh nhiet o cao hn se xay ra vi toc o ln hn.

+ Hang so toc o phan ng va do o, toc o phan ng se thay oi manh theo nhieto oi vi cac phan ng co nang lng hoat hoa ln. Ngc lai, cac phan ng conang lng hoat hoa be se co toc o phan ng thay oi rat t theo nhiet o.

+ ai lng E trong trng hp phan ng n gian, xay ra theo mot giai oan, lanang lng d toi thieu so vi nang lng trung bnh cua cac phan t nhiet o Ta cho ma cac phan t phan ng can phai co e tng tac gia chung co the co

hieu qua(xem H.III.2).

E2E1

I

II

III

Nang lng

Tien trnh phan ng

H.III.2: S o bieu dien hang rao nang lng cua phan ng hoa hoc.

II.Thuyet va cham hoat ong va thuyet phc chat hoat ong:1.Thuyet va cham hoat ong:

+ Quan iem cua thuyet va cham:

e phan ng hoa hoc xay ra, cac phan t tham gia phan ng, trc het,phai va cham vi nhau. Tuy nhien khong phai va cham nao cung dan en phanng ma ch nhng va cham gia cac phan t co nang lng ln hn hoac bangnang lng hoat hoa va phai co nh hng thch hp oi vi nhau mi co hieuqua.

+ Bieu toan hoc cua thuyet va cham:

Tren c s quan iem tren va tren c s l thuyet ong hoc phan t, thuyet vacham a thiet lap c cong thc cua mnh nh sau:

(III-13), trong o p la tha so nh hng khong gian ac trng

cho s nh hng thuan li, p thng co gia tr t 1 en 10 -10va Zola tha so trc

luy tha (bang hang so).

RT/E

oe.Z.pk =



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2.Thuyet phc chat hoat ong:+ Quan iem cua thuyet nay la phan ng hoa hoc xay ra la nh s hnh thanh tcac tieu phan tham gia phan ng mot to hp tam thitrang thai chuyen tiep-goi la

phc chat hoat ong.V du:

A + BK* (AB)* C + D

kp

chat au phc chattrung gian

san pham phan ng

Phc chat hoat ong khong phai la mot hp chat hoa hoc ben ma no ch la mottrang thai chuyen tiep cua cac tieu phan trong luc phan ng, co mc nang lng cao;do o, no khong ben, de b phan huy e tao thanh san pham phan ng hoac chat au.

+ Bieu thc toan hoc cua thuyet phc hoat ong: RT/ER/Sup e.eh

kT.k

= (III-14).



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CHNG IV.PHAN NG QUANG HOA, PHAN NG DAY CHUYENVA KHAI NIEM VE XUC TAC.

I.Phan ng quang hoa:1.Khai niem:

Phan ng quang hoa la phan ng xay ra di tac dung cua anh sang. Noi chnh xachn, phan ng quang hoa la phan ng xay ra, trong o nang lng can cho s dienbien cua phan ng hoac can cho s kch thch phan ng c a vao he phan ngdi dang nhng dao ong ien t nh anh sang trong thay, tia t ngoai, tia hongngoai, ...

V du:

Cac phan ng tong hp nh hidroclorua, phosgen, ...Phan ng phan huy H2O2, AgCl, AgBr, ...

Cac phan ng oxi hoa, quang hp, ...

Cac hien tng mat mau cua cac chat mau.

2.Mot so nh luat c ban cua phan ng quang hoa:a.nh luat Grothuss - Draper:Ch nhng bc xa nao c hap thu bi he phan ng mi co the gay nen s bien

oi hoa hoc. Tuy vay, cung can hieu rang, mac du phan ng quang hoa ch xay ra khichat phan ng hap thu cac bc xa nhng khong phai he co s hap thu bc xa la co sbien oi hoa hoc. Trong nhieu trng hp, mot phan hoac toan bo bc xa bien thanhnhiet, ngha la nang lng bc xa ch lam tang chuyen ong nhiet cua cac phan thap thu bc xa ma thoi. ieu o co ngha la, neu noi nhng bc xa b hap thu eugay nen phan ng la khong ung.

b.nh luat Bunsen - Roscoe:Tac dung hoa hoc cua bc xa ty le thuan vi tch so cua cng o anh sang (I) va

thi gian (t) cua no.

nh luat Bunsen - Roscoe ch gan ung, v khong phai tat ca nang lng b hapthu eu cung cap cho qua trnh hoa hoc.

c.nh luat ng lng quang hoa cua Einstein (Anhstanh):nh luat nay la nh luat tong quat va quan trong nhat oi vi phan ng quang

hoa. nh luat nay phat bieu nh sau: e phan ng c trong mot phan ng quanghoa, moi phan t chat phai hap thu mot lng t bc xa a gay nen phan ng.

Mot mol chat khi chu s bien oi trong phan ng quang hoa se nhan mot nanglng la: (jun/mol) (IV-1), trong o: N la so Avogadro ( ), h la

hang so Planck ( jun.giay) va

=N h. . 6 021023, .

=

6 2210

34

, . la tan so cua bc xa b hap thu.Ma (XI-2), trong o: c la toc o anh sang ( =c / 31010. cm/giay) va la o dai



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cua song anh sang (tnh bang n v cm). Nhng thng ngi ta hay bieu th o daicua song anh sang bang n v angstron, ngha la 10-8cm, nen phng trnh (IV-2)c viet la: (IV-3). = 108 . /c

T cac phng trnh (IV-1,3), ta suy ra:

E N h c=

. ..

108 (jun/mol) (IV-4) =E

N h c. .

, ..

4 18410

8

(cal/mol) (IV-5).

a cac gia tr N, h va c vao phng trnh (IV-5), sau khi bien oi, ta c:

E=2 6859

105,

.

(kcal/mol) (IV- 6), trong o: tnh bang n v Ao(angstron).

T phng trnh nay, ta thay rang nang lng do phan t hap thu phu thuoc vao odai song cua dao ong ien t va ty le nghch vi no. Dao ong ien t co o dai

song ngan nhat se co nang lng ln nhat va co hoat ong hoa hoc manh nhat.3.Hieu suat lng t:Thc nghiem ch ra rang, trong nhieu trng hp, so phan t a phan ng trong

phan ng quang hoa khong bang so lng t b hap thu. V vay, e ac trng chophan ng quang hoa, ngi ta a ra khai niem hieu suat lng t ( ). Hieu suatlng t la ty so gia so phan t cua chat a phan ng va so lng t anh sang b hapthu, tc la:

=

so phan t cua chat a phan ng

so lng t anh sang a b hap thuTuy thuoc vao o ln cua hieu suat lng t ma ngi ta chia cac phan ng

quang hoa ra thanh 4 loai sau ay:

+ Cac phan ng trong o =1, v du: s tao thanh bromciclohexan, s phan huy H2S

trong dung dch benzen, ...

+ Cac phan ng trong o 1, v du: s tao thanh hidrobrmua, s phan huy nitdioxit,

...

+ Cac phan ng trong o >>1, v du: phan ng tao thanh hidroclorua t hidro va clo,

phan ng clo hoa metan, ...

Theo nh luat ng lng quang hoa th hieu suat lng t phai bang 1. Tuy vay,s sai lech cua hieu suat lng t so vi 1 khong co ngha la nh luat ng lngquang hoa khong ung.

Qua thc nghiem, ngi ta thay rang phan ng quang hoa c tao thanh t cacphan ng s cap va thng tiep theo la cac phan ng th cap.

Nguyen nhan cua s sai lech co the giai thch nh sau:



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Trong phan ng quang hoa s cap, moi phan t b bien oi la do s hap thu trctiep mot lng t bc xa (v vay, =1). Nhng sau o thng con xay ra phan ng th

cap; phan ng nay khong can nhan nang lng bc xa. Cac san pham cua phan ngs cap se tiep tuc phan ng vi cac chat phan ng (v vay, >1). Trong nhng trnghp nhng bc xa do nhng phan t chat phan ng hap thu b tieu dung mot phan vaonhng qua trnh phu nao o (v du: khi va cham, nang lng d cua phan t ctruyen sang phan t cua mot chat khac) hoac chung c nhng phan t cua cac chatkhac cha trong he hap thu th


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c.Phan loai phan ng day chuyen:Ngi ta chia cac phan ng day chuyen thanh 2 loai sau ay:

+ Phan ng day chuyen khong phan nhanh: la phan ng trong o moi tieu phan hoat

ong khi tham gia bien oi sinh ra khong qua mot tieu phan hoat ong mi. Phan ngtong hp hydroclorua t clo va hydro la phan ng day chuyen khong phan nhanh.

+ Phan ng day chuyen phan nhanh: la phan ng trong o t mot tieu phan hoat ongsinh ra 2, 3, ... tieu phan hoat ong mi.

V du ve phan ng day chuyen phan nhanh: phan ng tong hp nc t hidrova oxi xay ra theo c che sau ay:

H H

H O HO O

HO H H O H

O H HO H

H H

2

2

2 2

2

2

2

2

+ +

+ +

+ +

2.ac iem cua phan ng day chuyen:So vi cac phan ng hoa hoc thong thng, phan ng day chuyen co nhng ac

iem khac biet la:

+ Mot trong nhng ac iem quan trong nhat cua phan ng day chuyen, co anhhng en toc o phan ng, la o dai mach, ngha la so nhng phan t cua motchat au a phan ng nh mot tac dung sinh mach. Ve ieu nay, cac phan ng cothe khac nhau trong nhng gii han rat rong va o dai mach co the phu thuocnhieu vao ieu kien dien bien cua phan ng. Co nhng phan ng o dai mach ratbe, ch khoang hai hoac ba mat xch; nhng cung co nhng phan ng co o daimach at ti hang nghn va hn the na mat xch.

o dai mach cua mot phan ng phu thuoc vao quan he gia so tieu phan hoatong c hnh thanh trong mot n v thi gian va so tieu phan o dung vao viec

hnh thanh cac san pham phan ng va cac qua trnh khac; noi cach khac, o daimach phu thuoc vao quan he gia so mach sinh ra trong mot n v thi gian va somach mat i trong cung khoang thi gian o.

+ Toc o phan ng day chuyen phu thuoc vao kch thc, hnh dang va chatlieu lam bnh phan ng.

Cac tieu phan hoat ong co the b tieu ph vao cac tng tac phu. Trong so cactng tac nay, s va cham vi thanh bnh hoac vi cac phan t tr trong bnh co motvai tro ac biet quan trong. V trong cac va cham o, cac phan t hoat ong thngmat nang lng d cua chung va tr thanh cac phan t khong hoat ong va v vay,

trong nhng qua trnh o, ngi ta thay co xay ra s ngat mach. S ngat mach o lam



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giam kha nang phat trien xa hn cua phan ng va trong nhng trng hp khongthuan li th ieu o co the lam dng han phan ng lai.

+ Phan ng day chuyen rat nhay vi s co mat cua chat la. Ch can co dau vet

cua chat la la co the lam tang hay giam toc o phan ng.+ Vi nhng phan ng no theo c che day chuyen co ton tai mot gii han ap

suat va qua trnh no ch xay ra trong vung gii han ap suat o. Neu ap suat caohn hoac thap hn gii han o th khong xay ra s no.

3.ong hoc cua phan ng day chuyen:a.ong hoc cua phan ng day chuyen khong phan nhanh:

Phan ng day chuyen khong phan nhanh la phan ng phc tap, chat au vasan pham phan ng b tieu thu va tao thanh trong cac qua trnh phat trien mach. Doo, toc o phan ng day chuyen tnh theo mot cau t nao o bang toc o cua giaioan phat trien mach, trong o cau t nghien cu b tieu thu hoac c tao thanh.

V vay, neu co mot mat xch gom hai phan ng th cap, trong o moi phanng eu co s tieu thu chat au va tao thanh san pham, ngha la:

; , trong o: va la cac

goc t do, th ta co:

R A R Bk

1 1 2 11 + + R A R Bk2 2 1 2

2 + + R1 R2

= = dC

dt

dC

dtk C C

A B

R A1 1

1 11. . (IV-7) va

= = dC

dt

dC

dtk C C

A B

R A2 2

2 22 . . (IV-8).

Muon viet phng trnh vi phan cho nong o goc t do, ta phai ke en toc ocua phan ng sinh mach (vsm=vo) va toc o cua phan ng ngat mach ( ).v vngm Ri=

Bnh thng, phan ng sinh mach se tao ra mot trong cac goc t do nao o etham gia vao phan ng day chuyen, v du: .R1

Neu k hieu va la toc o mat goc t do va th ta co:vR1

vR21R R2

+=12211

1

RRA2RA1o

RvC.C.kC.C.kv

dt

dC(IV-9) va

dC

dtk C C k C C v

R

A R A R

2

1 1 2 2 21 2

= . . . . R (IV-10).

V cac goc t do la cac tieu phan trung gian rat hoat ong nen trong toan bo qua

trnh phan ng, nong o cua chung c xem nh dng, ngha la:dC

dt

dC

dt

R R1 2 0

+ =

nen (IV-11). +=21 RRo

vvv



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Nh vay, trong che o dng, toc o ngat mach bang toc o sinh mach; v vay,neu xem ngat mach ch do mat mot trong cac goc t do th phng trnh (IV-11) se la

(IV-12).=iRo

vv

+ Xet trng hp ngat mach bac 1 (tc la Rikh) th ta co: (IV-

13) va vp=

Ri k 3

= iR3o C.kv

iA

3

oi C

k

vk (IV-14) (theo cac phng trnh (IV-7,8 ,13)).

+ Xet trng hp ngat mach bac 2 (tc la ) th ta co: (

IV-15) va vp=

2 3 2Rik

i

R 2R3o i

C.k2v =

3

oAi

k2

vCk

i (IV-16) (theo cac phng trnh (IV-7,8,15)).

+ Neu ta chia toc o cua phan ng day chuyen cho toc o cua phan ng ngat mach

hoac sinh mach th ta se thu c o dai mach ( )cua phan ng day chuyen khongphan nhanh la:

- Trng hp 1: ngat mach bac 1, ta co: = k

kCi A i

3

(IV-17).

- Trng hp 2: ngat mach bac 2, ta co:iA

o3

i Cv.k2

k= (IV-18).

+ Sau ay la mot so v du ve viec tnh toc o cua phan ng day chuyen khong phannhanh:

- V du 1: Chng minh rang phan ng: spHCOOHCl2 + , tuan theo phng trnh

ong hoc sau: =dC

dtk C CHCOOH Cl HCOOH. .2 , biet rang c che cua phan ng nh sau:

(sinh mach)Cl Clh k20 2 ,

Cl HCOOH HCl HOOC

HOOC Cl HCl CO Cl

k

k

+ +

+ + +

1

2

2 2

OH

(phat trien mach)

Cl thanh bnh hap phu (ngat mach) + k Cl3

Giai:

V ngat mach bac 1 oi vi Cl nen ki=k1va

C CA HCOi = va v nen

ta co:vp=

2Cloo C.kv =

HCOOH

3

Clo

1A

3

oi C

k

C.kkC

k

vk 2

i= = , trong o:k =k C CCl HCOOH. .2

3

1o

k

k.k.

- V du 2: Chng minh phng trnh ong hoc cua phan ng clo hoa C2Cl4trong CCl4

la =dC

dt

k CC Cl

Cl2 4

2

3 2. / , biet rang c che cua phan ng la:



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(sinh mach)Cl Clh k20 2

,

(phat trien mach)Cl C Cl C Cl

C Cl Cl C Cl Cl

k

k

+

+ +2 4 2 5

2 5 2 2 6

1

2

5 Cl

(ngat mach)2 2 5 2 6 2 43C Cl C Cl C Clk +

Giai:

V ngat mach bac 2 oi vi nen ki=k2va CC Cl2 CA i = 2 va v nen

vp =

2Cloo C.kv =

3

oAi

k2

vCk

i =

3

Clo

Cl2k2

C.kCk 2

2 = , trong o:k CCl.

/

2

3 2

2/1

3

o2

k2

kkk

= .

b.ong hoc cua phan ng day chuyen phan nhanh:Phng trnh ong hoc thng dung e mo ta cho phan ng day chuyen phan

nhanh la: n.vdt

dnv o +== (IV-19), trong o: n la nong o tong cong cua cac goc

t do, vola toc o sinh mach,. la hieu gia toc o sinh nhanh va toc o ngat mach.

Neu ca hai qua trnh sinh nhanh va ngat mach eu la phan ng bac 1 oi vinong o goc t do th toc o cua chung co the viet di dang f.n va q.n . Khi o, ta

co:dn

dtv f q n v q f = + = 0 0( ) ( )n (IV-20).

+ Neu q > f th he phan ng se co trang thai nong o dng cua goc t do sau mot thi

gian nao o, nen ta co: n v

q fd=

0 (IV-21). Ta thay rang neu f = 0 th nd= vo/q (IV-

22). Neu so sanh 2 phng trnh (IV-21) va (IV-22) th ta se thay rang nong o dngcua phan ng day chuyen khong phan nhanh nho hn nong o dng cua phan ngday chuyen phan nhanh.

+ Neu q < f th f -q=>0 va lay tch phan phng trnh (IV-19) tren, ta c:

(n v

e t= 0 1

) (IV-23). T phng trnh nay, ta thay rang n tang nhanh theo thi

gian va se co nguy c dan en s no.+ ac iem ac trng cua phan ng day chuyen phan nhanh la co hai che o dienbien rat khac nhau nh sau:

- Neu toc o cua phan ng ngat mach ln hn toc o cua qua trnh sinh nhanh th seco che o dng va trong a so cac trng hp, toc o phan ng nho en mc khongthe o c.

- Neu toc o cua qua trnh sinh nhanh ln hn toc o cua phan ng ngat mach th toco phan ng se tang len khong ngng va se ket thuc bang s no.

+ Ta co the ieu khien chut t mot trong nhng thong so quyet nh en toc o cuaphan ng ngat mach va toc o cua qua trnh sinh nhanh nh ap suat, nhiet o, thanh



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phan hon hp, kch thc, hnh dang va trang thai bnh phan ng, ... Hien tng thayoi chut t cac thong so co the chuyen t trang thai dng (xay ra cham) sang trangthai no (xay ra nhanh) hoac ngc lai trong ong hoa hoc goi la hien tng ti hanhay gii han (xem H.IV.1).

vung khong no vung no

giihan

noth

nhat

giihanno

thhai

giihan

noth

ba

P

T H.IV.1: Gii han no cua phan ng day chuyen phan nhanh.

III.Nguyen ly nong o on nh va viec ap dung nguyen ly nay trong viec xacnh phng trnh ong hoc cua phan ng phc tap:

1.Noi dung cua nguyen l nong o on nh (hay con goi la nguyen l nong o dng):Nong o chat trung gian (goc t do, phc chat hoat ong, ...) sau mot thi gian

phan ng c on nh, tc la ao ham cua nong o cua no theo thi gian bangkhong.

2.Ap dung nguyen l nong o dng trong viec xac nh phng trnh ong hoc cuaphan ng phc tap:

V du: cho phan ng tong hp hidrobromua xay ra theo c che sau:

Br Br Br H HBr H

H Br HBr Br H HBr H Br

Br Br

k k

k k

k

2 2

2 2

2

1 2

3 4

5

2

2

+ +

+ + + +

,

,

Hay chng minh:dC

dt

k C C

k C

C

HBr H Br

HBr

Br

=+

. .

.

/

/

2 2

2

1 2

1.

Giai:

+ Theo c che phan ng, ta co:

dC

dtk C C k C C k C CHBr H Br Br H HBr H= + 2 3 42 2. . . . . . (a)

+ Ap dung nguyen l nong o dng oi vi va , ta co:H Br



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dC

dtk C C k C C k C CH H Br Br H HBr H

= = 0 2 3 42 2. . . . . . (b)

vadC

dtk C k C C k C C k C C k CBr

Br H Br Br H HBr H B

= = + + 0 2 21 2 3 4 5

2

2 2 2

. . . . . . . .r

(c)

+ T cac phng trnh ( a, b, c), ta suy ra:

dC

dt

k k

kC C

k

k

C

C

HBr

H Br

HBr

Br

=

+

2

1

21

5

1 2

1 2

4

3

2 2

2

/

/. .

=+

k C C

k C

C

H Br

HBr

Br

. .

.

/

/

2

2

1 2

1

2 , trong o:

k k k

k=

2 2

1

5

1 2/

va k k

k

/ = 4

3

(ieu phai chng minh).

IV.Khai niem ve xuc tac:1.nh ngha:

Xuc tac la hien tng thay oi toc o phan ng gay ra do tac dung cua mot sochat goi la chat xuc tac. Chat c goi la chat xuc tac khi chat nay sau khi thamgia vao qua trnh phan ng th cuoi cung khong b thay oi ve lng cung nh vechat.

Chat xuc tac lam tang toc o phan ng goi la chat xuc tac dng va thng goila chat xuc tac.

Chat xuc tac lam giam toc o phan ng goi la chat xuc tac am va thng goi lachat c che.

Co mot so chat, du lng rat be, khi co mat trong he phan ng th lam giamhoac mat kha nang hoat ong cua chat xuc tac, goi la chat au oc xuc tac.

Ngc lai, co mot so chat, khi co mat trong he th lam tang hoat tnh cua chatxuc tac, goi la chat kch thch hay con goi la chat mang.

Ngi ta chia cac phan ng xuc tac thanh phan ng xuc tac ong the va phanng xuc tac d the.

Phan ng xuc tac ong the la phan ng trong o chat xuctac nam cung pha vi cac chat tham gia phan ng. Chat xuc taccho loai phan ng nay thng la cac dung dch acid, baz, muoicua kim loai chuyen tiep.

V du: phan ng iod hoa aceton nh xuc tac acid.

Phan ng xuc tac d the la phan ng trong o chat xuc tac nam khac phavi cac chat tham gia phan ng. Chat xuc tac cho loai phan ng nay thng la chat

ran (thng la kim loai va oxit kim loai) va phan ng se xay ra tren be mat chatxuc tac.



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Ngoai ra, con co loai phan ng xuc tac men, trong o men la chat xuc tac.

2.ac iem cua hien tng xuc tac:+ Co tnh chon loc cao: moi chat xuc tac thng ch xuc tac cho mot phan ng nhat

nh hoac mot loai phan ng nhat nh.+ Chat xuc tac lam tang toc o phan ng ch khong lam dch chuyen can bang hoahoc, tc la chat xuc tac lam tang toc o phan ng thuan bao nhieu lan th cung lamtang toc o phan ng nghch bay nhieu lan.

+ Chat xuc tac lam tang toc o phan ng cua nhng phan ng von d co kha nangxay ra mac du het sc cham ch khong gay nen phan ng, tc la chat xuc tac lamgiam nang lng hoat hoa cua phan ng ch khong lam thay oi trang thai au vatrang thai cuoi ( khong oi).G



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* BAI TAP ONG HOA HOC *BAI 1:Hang so can bang cua phan ng thuan nghch sau ay:

A Bk1k2

la 10, con hang so toc o cua phan ng thuan k1= 0,2 sec-1.

Hay xac nh thi gian e CA= CB, biet rang ban au ch co A.

GIAI:

Ta co: k kt x

1 2

1+ =

ln

; K = k1/k2=10 va k1= 0,2 sec-1k2= 0,02 sec-1.

= +

K a b

K

.

1=

10 0

10 110 11

aa

+ = / . V CA= CBnen ta suy ra: a - x = x a - x =

x =a/2. Ta suy ra: t =+

1

0 2 0 02

10 11

10 11 23 63

, ,ln

/

/ /,

a

a a(sec).

--------------------------------------------

BAI 2:Cho phan ng noi tiep: , co cac thong so ac trng sauay:

A Bk k1 2 C

Khi nong o chat B at cc ai thC

C

A

B=4 5, ; con thi gian e o bien oi

chat A la 25% la 85 sec.

Hay tnh k1va k2.

GIAI:

+ Nh chung ta a biet, C a k

kAt

k

k k

max.=

1

2

1

2 1

(a), C a k

kB

k

k k

max .=

1

2

2

2 1

(b) va

k t

a

a x1

1

= ln (c).

+ T cac phng trnh (a, b) va bai ra, ta co:C

C

k

k

At

B

max

max

,= =2

1

4 5 (d).

+ Theo bai ra, khi t= 85 sec th x = 25%.a nen t phng trnh (c), ta co:

k a

a a1

31

85 0 253 3810=

ln

, ., . (sec-1) (e).

+ T cac phng trnh (d, e), ta suy ra: k2= 15,21.10-3sec-1.

------------------------------------------------



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thi iem t bang 10 giay, tng ng la 0,5 mol/l, 0,03

mol/l, 0,02 mol/l, 0,3 mol/l, 0,15 mol/l. Biet ban au, nong o cac chat B, C, D, E eubang khong.

C C C C CA B C D, , , , E

Hay tnh va theo n v phut-1

.k k k1 2 3, , k4

GIAI:

+ Cong thc:

EDCB

EDCBAoA

A

oA

CCCCkkkk

CCCCCC

C

C

tkkkk

::::::

ln1

4321

4321

=

++++=

=+++

+ Tnh toan: thay cac d kien bai ra vao cac cong thc tren; sau o, giai he cacphng trnh, ta tnh c va tng ng la 0,2496 phut-1, 0,1664 phut-1,

2,496 phut-1va 1,248 phut-1.

k k k1 2 3, , k4

---------------------------------------------

BAI 5:Nong o cac chat A, B va C trong dung dch X eu la a mol/l. Sau 1000giay, mot na lng chat A a phan ng.

Neu phan ng xay ra trong dung dch X la phan ng bac mot, bac hai, bac bava bac khong th sau 2000 giay se con lai bao nhieu % chat A so vi ban au?

GIAI:Ta xet cac loai phan ng bac 1, 2, 3 va 0 (s dung phng trnh ong hoc

dang tch phan khi nong o ban au cua cac chat giong nhau) th ta se thu c apso tng ng vi phan ng bac1, 2, 3 va 0 la 25%, 33,33%, 37,8% va 0%.

-----------------------------------------------

BAI 6: Cho phan ng nhiet phan kh N2O5xay ra theo c che sau:

N2O5 NO2 NO3k1k2

+

NO NO NO NO O

NO N O NO

k

k

2 3 2

2 5 2

3

4 3

+ + +

+ 2

Hay ap dung nguyen l nong o dng oi vi NO3va NO e tm phng trnhtnh toc o cua phan ng co c che tren.

AP SO: =+

dC

dt

k k

k kC

N O

N O

2 5

2 5

2 1 3

2 3

..



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Phan II.IENHOAHOC.CHNG V.DUNG DCH CAC CHAT IEN GIAI.

I.Tnh chat chung cua dung dch:1.o giam ap suat tng oi cua dung moi tren dung dch so vi dung moi nguyenchat la:

2o

1

1

o

1 NP

PP=

(V-1), trong o va P1la ap suat hi bao hoa cua dung moi tinh

khiet va cua dung moi tren dung dch tng ng, N2 la nong o phan mol cua chat tantrong dung dch.

o

1P

2.o tang nhiet o soi va o ha nhiet o ong ac cua dung dch so vi dung moinguyen chat la:

TS =TS -TSo =ES .m2 (V-2), T=To -T=E.m2 (V-3), trong o TS ()la otang nhiet o soi (o ha nhiet o ong ac), TS va TSo la nhiet o soi cua dung dch vadung moi tng ng, T va To la nhiet o ong ac cua dung dch va dung moi tngng, ES va Ela hang so nghiem soi va nghiem lanh tng ng, m2la nong o molancua chat tan trong dung dch.

3.Ap suat tham thau cua dung dch la:=C2.RT (V-4), C2= n2/V, trong o la ap suat tham thau, n2la so mol chat

tan, V la the tch dung dch, C2la nong o mol cua chat tan, R la hang so kh va T lanhiet o tuyet oi.

II.Dung dch cac chat ien giai:1.Tnh chat cua dung dch cac chat ien giai:+ o dan ien kha cao do trong dung dch co cac ion t do.

+ oi vi dung dch cac chat ien giai, ta co cac he thc sau:

P= =i.P1o.N2 (V-5); TS ()=i.ES ().m2 (V-6); =i.C2.RT (V-7), trong o:

i1 va khi dung dch vo cung loang th i la 1 so nguyen n gian 2, 3, 4, con bnhthng i la so thap phan.

1

o

1 PP

2.Thuyet Areniuyt ve s ien li:+ Cac phan t chat tan trong cac dung dch chat ien giai chu s phan li thanhnhng ion dng (cation) va ion am (anion). Cac ion nay se tham gia vao s danien.

+ S phan li c coi nh la 1 phan ng hoa hoc, tuan theo nh luat tac dung khoilng nh nhng phan ng hoa hoc khac.



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[ H A ]

[ H+ ] [ A- ], K =A-+H+V du: HA K la hang so phan li,

+ Cac chat ien giai trong dung dch co o phan li nhat nh tuy thuoc vao tnh chatcua chung. o phan li c nh ngha la t so gia so phan t a phan li n' vatong so phan t luc au n, tc la = n'/n (01).

Thuyet Areniuyt giai thch c s sai lech gia dung dch noi chung va dung dchcac chat ien giai la: do s phan li cua cac phan t chat tan ma lam cho so tieu phanthc te trong dung dch chat ien giai tang len so vi khi khong co s phan li va vvay, o giam ap suat hi tng oi cua dung moi tren dung dch tang len, o ha nhieto ong ac, o tang nhiet o soi va ap suat tham thau tang len.

Moi lien he gia he so ang trng i va o phan li nh sau: i=1+( -1) (V-

8), trong o la so ion do 1 phan t phan li ra.

V du:* Dung dch NaCl loang co i=1+1(2-1)= 2.

* Dung dch K3PO4 loang co i=1+1(4-1)= 4.

III.o dan ien cua dung dch chat ien giai:+ Khi co dong ien 1 chieu i qua chat dan ien loai 2, lng ien c chuyen vecac ien cc la nh cac ion t do. Nhng ion dng (cation) chuyen ve ien cc am(catod), con nhng ion tch ien am (anion) chuyen ve ien cc dng (anod).

+ ien tr trong dung dch chat ien giai (R) cung giong nh trong bat k chat danien nao phu thuoc vao ban chat cua chat dan ien, tiet dien ngang va chieu dai cuano, tc la R=.l/s, trong o la ien tr rieng cua chat dan ien phu thuoc vao banchat cua no, l la chieu dai va s la tiet dien ngang (xem H.V.1).

lS

dung dch chat ien giai

H.V.1: S o ien tr cua dung dch chat ien giai.

Khi l=1cm va s=1cm2th R=. Nh vay, ien tr rieng la ien tr cua 1 chatdan ien co chieu dai 1cm va co tiet dien ngang la 1 cm 2.

+ Trong ien hoa, ngi ta thng anh gia tnh chat dan ien cua chat dan ienbang ai lng nghch ao cua ien tr rieng va c goi la o dan ien rieng ().



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=1 (V-9), o dan ien rieng co th nguyen la -1.cm-1.

+ S phu thuoc cua o dan ien rieng vao nong o dung dch nh sau: const..C

(V-10) va o th -C se la mot ng cong co cc ai co dang nh tren H.V.2.

=

H.V.2: o th -C H.V.3: o th -C H.V.4: o th -C1/2.

+ e tien li hn trong viec nghien cu, ngi ta thng s dung cai goi la o danien ng lng. o dan ien ng lng lien he vi o dan ien rieng theo hethc:

=1000/C (V-11), trong o C la nong o ng lng. Th nguyen cua o danien ng lng la -1.cm2.lg-1.

o dan ien ng lng phu thuoc vao nong o dung dch (xem H.V.3). Khinong o dung dch giam th o dan o dan ien ng lng tang. Vi s pha loangdung dch, o dan ien se tang len en 1 gia tr gii han nao o. Gia tr gii han cua odan ien ng lng goi la o dan ien khi pha loang vo cung va c k hieu la

hay o. Khi C0 th 1, ngha la chat ien giai phan li hoan toan, luc o ta co o.Ngc lai, khi C tang th giam, do o giam.

S phu thuoc cua o dan ien ng lng cua chat ien giai manh vao nong oco dang nh tren H.V.4 va a c Conraus a ra cong thc thc nghiem sau ay:

=o-A.C1/2=o-A1.C1/2-A2.C1/2(V-12), trong o A, A1va A2la cac hang so kinhnghiem.

+ o dan ien khong nhng phu thuoc vao tong so ion co mat trong dung dch macon phu thuoc vao o nht cua dung dch va nhiet o.

- Khi tang nong o th o nht cua dung dch tang; do o, lam giam toc o chuyenong cua cac ion va v vay, o dan ien giam.

- Khi tang nhiet o th o nht cua dung dch giam, do o o dan ien tang (khac vichat dan ien loai1).

+ o dan ien khi pha loang vo cung cua chat ien giai bang tong o dan ien khipha loang vo cung cua cac ion tao nen chat ien giai o, tc la: o=o++o-(V-13).



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IV.Phng phap o o dan ien va ng dung cua no:1.Phng phap o:

a.ieu kien:e o o dan ien cua dung dch chat ien giai can phai:

+ o c nhiet o chnh xac va gi c nhiet o khong oi trong suot qua trnho.

+ Loai tr c s phan cc ien cc.

+ o chnh xac cac ai lng ien.b.Nguyen tac:Dung cau Vettn e o ien tr cua dung dch, t o suy ra o dan ien.

c.Cau tao cua cau Vettn:c neu ra tren H.V.5.

R1R2

RxR3

G

E~

H.V.5: S o cau tao cua cau Vettn gom: E la nguon ien xoay chieu, R

1va R2la cac bien tr, R3la ien tr so sanh a biet, Rx la ien tr cua dung dch cano, G la dung cu o iem khongcua dong ien (ong nghe, galvanomet, ).

d.Cach o:ieu chnh R1 va R2sao cho dong ien i qua G=0, luc o ong nghe khong keu

hay keu nho nhat, ta at c can bang cau. Theo nh luat Kiecsop (Kirchhoff),ta co: Rx/R3=R1/R2Rx=R1.R3/R2. Ma Rx= l / S. nen suy ra: =l/S.Rx.

Viec xac nh l/S trong thc te la rat kho chnh xac nen ngi ta thng co nhl/S=k goi la hang so bnh va xac nh no nh vao viec o ien tr cua 1 dung dchmau a biet chnh xac o dan ien m.

Ta co: Rm=l/S.m=k/mk=Rm.m=Rm.m/Rx(V-14). T gia tr cua , ta cothe suy ra .

2.ng dung cua viec o o dan ien:a.Xac nh o phan li cua chat ien giai yeu:=C/0=C/(0++0-).

Nh vao viec o o dan ien, ta xac nh c C, con 0+va 0-co san trong

cac bang tra cu cua so tay hoa hoc, ta de dang xac nh c .



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b.Xac nh o tan cua chat t tan:Neu goi S la o tan cua chat t tan (ng lng gam/lit) th ta co:

=.1000/C=.1000/S. V chat t tan nen dung dch bao hoa cua no la dung dch rat

loang va v vay, ova do o, S=.1000/ o=.1000/(0++0-).c.Chuan o dan ien ke:+ Nguyen tac cua phng phap chuan o nay la da vao s khac nhau ve o danien cua cac ion. Trong qua trnh chuan o, tai iem tng ng, o dan ien seco s thay oi ot ngot.

+ V du: Khi chuan o dung dch HCl bang dung dch NaOH, dung dchCH3COOH bang dung dch NaOH th o th bieu dien s phu thuoc cua o danien () vao the tch dung dch NaOH cho vao nh tren H.V.6, H.V.7 tng ng.

VddNaOH VddNaOHVt Vt

H.V.6 H.V.7



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CHNG VI.NGUYEN TO GANVANIC.I.Cac khai niem m au:+ ien cc: la kim loai nam tiep xuc vi dung dch chat ien phan.

V du: Zn / Zn2+, Cu / Cu2+,

+ Nguyen to ganvanic: la he cac ien cc khac nhau b ngan cach bi 1 lp dung dchchat ien phan, co kha nang sinh cong ien, c dung lam nguon ien.

V du: nguyen to anien-Jacobi la nguyen to ganvanic c tao thanh t 2 kimloai Zn va Cu nhung trong 2 dung dch muoi cua chung (Cu/Cu2+va Zn/Zn2+) va cacdung dch tiep xuc vi nhau qua mang ngan xop.

+ Cach viet cau tao cua nguyen to ganvanic:

- Ranh gii kim loai-dung dch c k hieu bang 1 net ng, ranh gii dung dch-dung dch c k hieu bang 2 net ng.

-T trai sang phai lan lt ngi ta at ien cc am, dung dch cua ien cc am,cau noi, dung dch cua ien cc dng va cuoi cung la ien cc dng.

V du: nguyen to anien-Jacobi c viet la: (-) Zn/Zn2+//Cu2+/Cu (+).

+ The ien cc: la the xuat hien tren ranh gii kim loai-dung dch cua ien cc. Theien cc co the xac nh c bang cach o sc ien ong cua nguyen to ganvanicc cau tao gom ien cc o va ien cc so sanh co the a biet (ien cc hydro tieu

chuan co the bang khong, ien cc calomen co the bang 0,2412von, ).+ Sc ien ong cua nguyen to ganvanic: la hieu cua 2 the ien cc.

V du: nguyen to anien-Jacobi co sc ien ong:

E= + = + +Cu Cu Zn Zn2 2/ / .

II.The cua tng ien cc:The cua tng ien cc rieng biet c o bang cach so sanh no vi 1 ien cc

khac tao thanh nguyen to ganvanic. ien cc so sanh la ien cc co the a biet va

tng oi on nh (thng la ien cc hydro hoac ien cc calomen). Neu ien cc sosanh la ien cc hydro tieu chuan th dau cua the ien cc la dau dng neu trongnguyen to nay ien cc nghien cu la ien cc dng va ngc lai, la am neu iencc nghien cu la ien cc am. V sc ien ong luon luon dng (G=-nFE


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III.Phng phap o sc ien ong:1.Nguyen tac:

Cac nguyen tac thng dung e o sc ien ong cua nguyen to ganvanic (E) eu

da tren phng phap bo chnh Pogenooc. u iem cua phng phap nay la chonh phng phap bo chnh Pogenooc, ta co the xac nh c E khi mach h, noikhac i khi dong ien khong chay qua nguyen to ganvanic. Nguyen to ganvanic chco the coi la thuan nghch khi co 1 dong ien vo cung nho chay qua nguyen to. Doo, nguyen to ganvanic trang thai mach h la ieu kien l tng e o E cua no lamviec thuan nghch.

2.Bnh o E:H.VI.1 hoac H.VI.2.

E

ddMIn+ ddMII

n+

MII MI dd KCl bh

E ddKCl bh

MI MII

dd MIn+

dd MIIn+

H.VI.1 H.VI.2

3.Dung cu dung e o E (ien the ke) va cach o E:Dung cu dung e o E c ve tren H.VI.3 gom 1 nguon ien C noi xuong cac

au cua mot day dan ong nhat AB co ien tr cao. Nguon ien C la accu co scien ong on nh va ln hn sc ien ong can o. Nguyen to Ex noi au am viiem A la iem noi vi au am cua accu. ien cc th 2 (ien cc dng) cuanguyen to ganvanic c noi qua ien ke G ti con chay D. Con chay D se dchchuyen tren day AB en khi dong ien qua G bang khong (kim ien ke G ch sokhong). S sut the tren oan AD trong mach accu C se bo chnh mot cach chnh xacsc ien ong cua nguyen to Ex.

Ta bat cong tac k1 sang pha nguyen to chuan Et/c co sc ien ong a biet chnhxac. e kim ien ke G ch so khong phai dch chuyen con chay D sang v tr mi tren

oan AB la D. S sut the tren oan ADse bo chnh 1 cach chnh xac sc ien ongcua nguyen to Et/c.

V day dan AB ong nhat nen ta co: Ex/Eaccu=AD/AB va Et/c/Eaccu=AD/ AB; suyra: Ex=Et/c.AD/AD.



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C

k

k1

A B

G

D D'

Ex

Et/c

-

-

-

+

+

+

H.VI.3

IV.Cac qua trnh xay ra trong nguyen to ganvanic:1.Cac phan ng ien cc va phan ng chung:

Trong nguyen to ganvanic, ien cc nao co the am hn hoac t dng hn se laien cc am; ien cc o, se co s chuyen ion kim loai vao dung dch, tc la kimloai b hoa tan hay con goi la b oxihoa; con ien cc co the dng hn hoac t amhn se la ien cc dng va se b kh (tao ra tren ien cc kim loai hoac kh ,).Ket qua cua 2 phan ng ien cc la cho ta 1 dong ien chay qua day dan kim loai.

Nh vay, ien cc am, xay ra qua trnh oxihoa va ien cc dng, xay ra quatrnh kh; do vay, phan ng chung trong nguyen to ganvanic la phan ng oxihoa-kh.

V du: nguyen to anien-Jacobi ( - Zn/Zn2+//Cu2+/Cu +):

(-)Zn=Zn2++2e, qua trnh oxihoa (Zn b tan ra);

(+) Cu2++2e=Cu, qua trnh kh (Cu ket tua tren ien cc Cu);

va phan ng chung: Zn+Cu2+=Zn2++Cu.

2.Chieu dong ien:Trong nguyen to ganvanic, do cac phan ng ien cc ma lam cho cac e

chuyen qua day dan kim loai t ien cc co the am hn hoac t dng hn (ien ccam) sang ien cc co the t am hn hoac dng hn (ien cc dng); do o, dongdien trong day dan se i t ien cc dng sang ien cc am.

V du: nguyen to -Zn /Zn2+

/Cu2+

/Cu+, co chieu dong ien c ch ra trenH.VI.4.

e I

anod (- ) catod (+)

Zn Cu SO4

2- SO42-

Zn2+ Cu2+



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H.VI.4: S o ve chieu chuyen ong cua cac cation, anion, ien t va chieudong ien trong nguyen to anien-Jacobi.



47/127


CHNG VII.NHIET ONG HOC CUA CAC MACH IEN HOA VATHE IEN CC.

I.Moi lien he gia the ang nhiet ang ap G va sc ien ong cua nguyen toganvanic E va phng trnh the ien cc:+ Nh chung ta a biet trong nhiet ong hoc th Amax = -G=nFE (VII-1).

+ Xet nguyen to ganvanic: (-)MI/MIn+//MIIn+/MII (+).

- anod (-), xay ra qua trnh oxihoa sau: MI = MIn++ne.

- catod (+), xay ra qua trnh kh sau: MIIn+ +ne = MII.

- Phan ng chung: MI+MIIn+=MIn++MII .

- Khi phan ng at en trang thai can bang th theo nh luat tac dung khoi lng,

ta co: Ka a

a a

M M

M Mcb

In

II

IIn

I

=

+

+

.

.(VII-2) K

a

a

M

Mcb

In

IIn

=

+

+

(VII-3)

Theo nhiet ong hoc, ta co: G = RTlna

a

M

M

In

IIn

+

+

- RTln(a

a

M

M

In

IIn

+

+

)cb =-RT(lnK-lna

a

M

M

In

IIn

+

+

)

(VII-4) E=-G/nF= RT

nFlnK-

RT

nFln

a

a

M

M

In

IIn

+

+

=Eo -RT

nFln

a

a

M

M

In

IIn

+

+

(VII-5),

trong o: KlnnF

RTEo = (VII-6).

+ Phng trnh the ien cc tong quat (phng trnh Nec) nh sau:

Kh

Oxo

Kh/OxKh/Oxa

aln

nF

RT+= (VII-7).

25oC, phng trnh Nec nh sau:

Kh

Oxo

Kh/OxKh/Ox a

alg

n.23062

303,2.15,298.987,1+=

Kh

Oxo

Kh/Ox a

alg

n

059,0+= (VII-8).

II.The ien cc:1.Phan loai ien cc:

a.ien cc loai 1:+ Cau tao: la he gom kim loai hoac a kim c nhung trong dung dch cha ionkim loai hoac a kim o.

+ S o ien cc : M/ Mn+, A/ An-.

+ The ien cc:



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- oi vi ien cc kim loai:

Phng trnh phan ng ien cc: Mn++ne=M.

Phng trnh the ien cc: +++ += nnnM

o

M/MM/M

alnnF

RT(VII-9).

- oi vi ien cc a kim:

Phng trnh phan ng ien cc: A + ne = An-.

Phng trnh the ien cc:n

nn

A

Ao

A/AA/A a

aln

nF

RT

+= (VII-10).

+ Cac v du:

- V du 1: ien cc niken (Ni/Ni2+).

Phng trnh phan ng ien cc: Ni2++2e=Ni.

Phng trnh the ien cc: +++ += 222 Nio

Ni/NiNi/Ni aln

nF

RT.

-V du 2: ien cc clo ((Pt)Cl2/Cl-).

Phng trnh phan ng ien cc:Cl2+2e=2Cl- .

Phng trnh the ien cc: 2

Cl

Clo

Cl/ClCl/Cl a

Pln

F2

RT 2

22

+= .

b.ien cc loai 2:+ Cau tao: la he gom 1 kim loai c phu1 hp chat kho tan cua kim loai o(muoi hoac oxit) va c nhung vao dung dch cha anion cua hp chat kho tano.

+ S o ien cc : M,MA/An- .

+ The ien cc:

- Phng trnh phan ng ien cc: MA+ne=M+An-.

- Phng trnh the ien cc: nnn

AM

MAo

M,MA/AM,MA/A a.a

a

lnnF

RT

+= .

nnA

o

M,MA/A aln

nF

RT = (VII-11).

ien cc loai 2 co the ien cc rat on nh, de lap lai; do o, chung thngc dung lam ien cc so sanh.

+ Cac ien cc loai 2 ien hnh (quan trong trong thc te):

- ien cc calomen: (Pt)Hg, Hg2Cl2/Cl-.

Phng trnh phan ng ien cc: Hg2Cl2+ 2e = 2Hg + 2Cl-.



49/127


Phng trnh the ien cc:cal. =ocal.-RT

F2ln =ocal.-

2

Cla

RT

Fln .a

Cl

oi vi ien cc calomen, vi dung dch KCl bao hoa va nhiet o 250c,

the ien cc la 0,2412 von .- ien cc bac-bacclorua: Ag, AgCl / Cl-.

Phng trnh phan ng ien cc: AgCl + 1e = Ag + Cl-.

Phng trnh the ien cc: = Clo

Ag,AgCl/ClAg,AgCl/Cl aln

F

RT

+ Chu y: MAo

M/M

o

M,MA/A Tln

nF

RTnn += + (VII-12).

c.ien cc loai 3:+ Cau tao: la he gom kim loai tiep xuc vi 2 muoi kho tan co chung anion cnhung vao dung dch cha cation cua muoi kho tan th 2.

+ S o ien cc: M,MA,MA/Mn+(TMA


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- Phng trnh the ien cc:Kh

Oxo

Kh/OxKh/Oxa

aln

nF

RT+= (VII-16).

+ V du:

- Pt/Fe3+,Fe2+: Fe3++1e=Fe2+,2

3

2323

Fe

Feo

Fe/FeFe/Fe a

aln

F

RT

+

+

++++ += .

- Pt/H+,MnO4-, Mn2+:MnO4-+8H++5e=Mn2++4H2O

2

4

24

24

Mn

8

HMnOo

Mn/H,MnOMn/H,MnO a

a.aln

F5

RT

+

+

++++ += .

e.ien cc hon hong:+ Cau tao: la he gom hon hong cua 1 kim loai tiep xuc vi dung dch cha ion kimloai o.

+ S o ien cc: (Hg)M/Mn+ .

+ Phng trnh the ien cc:

- Phng trnh phan ng ien cc:Mn++ne=M(Hg).

- Phng trnh the ien cc:)Hg(M

Mo

Hg,M/MHg,M/M a

aln

nF

RT nnn

+

++ += (VII-17).

+ V du:(Hg)Cd/Cd2+.

Cd2++2e=Cd (Hg),)Hg(Cd

Cdo

Hg,Cd/CdHg,Cd/Cd a

aln

F2

RT 222

+

++ +=

f.ien cc kh:+ Cau tao: la he gom 1 kim loai tr (Pt, Au, ) tiep xuc vi kh va dung dchcha ion cua kh o.

+ V du: ien cc hidro, ien cc clo,

+ Phng trnh the ien cc:

Xet ien cc hidro: Pt, H2/H+.

- Phng trnh phan ng ien cc: 2H++2e=H2.

- Phng trnh the ien cc:2

22

H

2

Ho

H/HH/H P

aln

F2

RT +++ += (VII-18).

25oc va =1 atm,2H

P pH.059,0alg059,0H

o

H/HH/H 22=+= +++

(VII-19), v va0o

H/H 2 = + pH a H= +lg .



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2.Mot so ng dung cua viec o sc ien ong:a.o o pH cua dung dch:+ Nguyen tac cua phep o la lap 1 nguyen to ganvanic gom 1 ien cc so sanh

(thng la ien cc calomen) va 1 ien cc co the phu thuoc vao pH cua dung dchc goi la ien cc ch th (thng la ien cc hydro, ien cc thuy tinh, ).

+ ien cc ch th la ien cc hydro:

Cau tao cua nguyen to ganvanic trong trng hp nay nh sau:

(-)(Pt), H2(P=1atm)/H+//KCl/Hg2Cl2,Hg (Pt) (+).

E = cal. + 0,059.pH pH E cal=

.,0 059

(VII-20).

+ ien cc ch th la ien cc thuy tinh:Cau tao cua nguyen to ganvanic trong trng hp nay la:

(-)(Pt)Hg, Hg2Cl2/KCl//H+/ien cc thuy tinh (+).

.cal

o

tt.caltt pH.059,0E ==059,0

EpH .cal

o

tt = (VII-21).

b.Chuan o ien the ke (chuan o o the):+ Nguyen tac: tai iem tng ng cua cac phan ng khac nhau (trung hoa, taophc, ket tua, oxihoa-kh,) c xac nh bang bc nhay the ac trng .

+ V du: chuan o dung dch NaCl bang dung dch AgNO3; muon vay, ta phai lapnguyen to ganvanic sau ay:

(-) (Pt) Hg, Hg2Cl2/KCl//NaCl/AgCl,Ag (+).

Trong qua trnh chuan o, ta o the cua na nguyen to ben phai hoac o E cuanguyen to tren, roi xay dng o th bieu dien s phu thuoc cua hoac E vao lngdung dch AgNO3them vao, o th o co dang nh tren H.VII.1.

E()

Vt VddAgNO3

H.VII.1: ng cong chuan o o the dung dch NaCl bang dung dch AgNO3.

Ta co:

(VII-22). === Clo

1.calCl

o

Ag,AgCl/Cl.calAg,AgCl/Cl alg059,0Ealg059,0E



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53/127


( ) =

+=

+

=K x10lg, lg , lg , lg

,K

a E a ax

Ag Ag CN CN0 059 0 059 0 118

0 059

2 (VII-

24).



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* CAC BAI TAP IEN HOA HOC *BAI 1: o dan ien ng lng cua dung dch acid acetic1,59.10-4M la 127,7-1.cm2.lg-1.Tnh hang so phan li cua acid acetic trong dung dch tren va tnh pH cuadung dch acid acetic tren. Cho

+

H,o=349,8 va COOCH,o 3

=40,9 -1.cm2.lg-1.

GIAI:

+ =349,8+40,9=390,7+ += COOCH,oH,oCOOHCH,o 33

=c/o=127,7/390,70,32685.

+ Phng trnh phan ng phan li:

CH3COOH CH3COO- H++

.

( )CC

C1Ka= =

2C

1 - = 0,316852.1,59.10-4/(1-0,32685)2,5234.10-5.

C =C=0,32685.1,59.10-4=0,5197.10-4pH=-lg =-lg5,197+5=4,2842.H+

CH +

---------------------------------

BAI 2:Tnh hang so can bang cua phan ng:Zn +Cd2+=Zn2++Cd va cong cua phanng nay trong ieu kien hoan toan thuan nghch ap suat va nhiet o khong oi. Chobiet: , =0,001, =-0,763 v va = -0,402v (nhiet o la

25oc).

aCd+

=2 0125, a Zn2+ o

Zn/Zn2+ o

Cd/Cd2 +

GIAI:

Eo= - =-0,402-(-0,763)=0,361 (v)oCd/Cd2 +

oZn/Zn 2+

Go= -nFEo=-RTlnKlgK=2.0,361/0,059 12,24K=1012,24.

Amax=nFE ma E=+--, =-0,402+0,0295lg0,125=-0,4286 (v) Cd Cd 2 + /

va =-0,763+0,0295lg0,001=-0,8515 (v).Zn Zn2 + /

E=-0,4286 -(-0,8515)=0,4229(v)Amax=2.23062.0,4229=19505,84 (cal/mol).

-----------------------------

BAI 3: Phai lap cac nguyen to ganvanic va cac ien cc nh the nao e trong oxay ra cac phan ng sau:

1. Cd+Cu2+=Cd2++Cu. 2. 2Ag++H2=2Ag + 2H+.3. H2+Cl2=2HCl.

4. Zn+2Fe3+ =Zn2++2Fe2+.



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GIAI:

1. (-)Cd=Cd2++2e (-) Cd/Cd2+; (+)Cu2++2e=Cu (+)Cu/Cu2+.Ta co: nguyen toganvanic la ()Cd/Cd2+//Cu2+/Cu (+).

2. Tng t, ta co: (-)(Pt)H2/H+//Ag+/Ag (+).

3. Tng t, ta co: (-) (Pt)H2/H+//Cl-/Cl2(Pt) (+).

4. Tng t, ta co: (-) Zn/Zn2+//Fe3+, Fe2+/Pt (+).

---------------------------------

BAI 4:Tnh sc ien ong cua cac nguyen to ganvanic tao bi cac ien cc kim loaighep vi ien cc calomen (cal.=0,2412 v, nhiet o la 25

oc).Xac nh dau cua iencc kim loai trong tng trng hp va viet cac phng trnh phan ng ien cc va

phan ng chung.

1. Ag/Ag+, co =0,5 va o=0,8 v.aAg+

2. Co/Co2+, co =0,063 va o=-0,277 v.aCo+2

3. Pb/Pb2+, co =1,26 va o=-0,126 v.aPb+2

GIAI:

1. =0,8+0,059lg0,50,782(v)>cal ien cc Ag/Ag+

la ien cc dng E=+--=0,782-0,2412=0,5408 (v).

Ag Ag Ag Ag Aga+ += +

/ / , lg0 0 059 +

Cac phng trnh phan ng:(-) 2Hg+2Cl-=Hg2Cl2+2e; (+) Ag++e=Ag; 2Hg+2Ag++2Cl-=Hg2Cl2+2Ag.

2. Tng t nh tren, ta suy ra: Co Co+2 /

=-0,312v; ien cc Co/Co+2la ien cc am;

E=0,5532v; cac phng trnh phan ng:(-) Co=Co2++2e;(+)Hg2Cl2+2e=2Hg +2Cl-;

Co+Hg2Cl2=Co2++2Cl-+2Hg.

3. Tng t nh tren, ta suy ra: Pb Pb+2 /

=-0,123v; ien cc Pb/Pb+2 la ien cc am;

E=0,3642v; cac phng trnh phan ng :(-)Pb=Pb2++2e;(+)Hg2Cl2+2e =2Hg + 2Cl-;

Pb+Hg2Cl2=Pb2++2Cl-+2Hg.



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Phan III.HOAHOCCHATKEO.CHNG VIII.KHAI NIEM VE CHAT KEO VA PHNG PHAPIEU CHE DUNG DCH KEO.

I.Khai niem ve chat keo:1.nh ngha he keo:

La he ma o tng phan tan -chat tan-c phan chia nho en trang thai tap hpcac phan t co kch thc c 1-100 mva c phan bo trong mot moi trng goila moi trng phan tan (dung moi). Toan bo he thong o goi la he keo hay dungkeo, o la he a phan tan va la he d the.

2.o phan tan (D):La ai lng nghch ao cua kch thc hat keo (a), tc la D = 1/a (cm -1).

Da vao kch thc hat cua tng phan tan hoac o phan tan, ta co the phan racac loai he sau:

D(cm-1) 10+7 10+5

Dung dchthat

Hekeo

He phan tan

vi d the

He phan tan tho

a(cm) 10-7 10-5

3.Tng phan tan va moi trng phan tan:a.Tng phan tan:

Co the la chat kh, chat long hoac chat ran.

b.Moi trng phan tan:Co the la chat kh, chat long hoac chat ran.

c.V du:Hon hp kh (K/K), sng mu hoac may (L/K), khoi hoac bui (R/K), bot (K/L), nhu

tng (L/L), huyen phu (R/L), bot ran (K/R), nhu tng ran (L/R), dung dch rannh hp kim, a qu, (R/R).

4.ac diem cua cac he keo:+ Co kha nang phan tan ang sang: khi chieu 1 chum anh sang manh vao dung

dch keo th thay uc v he keo la he d the.

+ Khuech tan rat cham do kch thc hat keo ln.

+ Khong ben vng tap hp, tc la de lien ket lai vi nhau thanh hat ln hn elam giam nang lng t do be mat, tc la de b keo tu.

+ Co kha nang tham tch, tc la cac hat keo khong i qua c mang ban tham.



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+ Thng co hien tng ien di (cac hat keo thng chuyen ong trong ientrng) v cac hat keo thng mang ien.

5.oi tng nghien cu cua hoa hoc chat keo:Nghien cu he keo, he vi d the, he tho va he ban keo.

6.Yngha cua hoa hoc chat keo:+ Vu tru la he keo khong loo la nhng am bui ln.

+ Cac hien tng kh tng co lien quan en hoa keo nh may, sng mu, tuyet,s tao thanh cac vung ong bang chau tho,

+ Co y ngha to ln trong tho nhng hoc, canh tac hoc. at la he keo phc tap;kch thc, hnh dang cung nh ban chat cua cac hat keo at quyet nh kha nangtham t, kha nang hap phu cua at cung nh gi cac ion xac nh trong at,

+ Trong cong nghiep, hau nh nganh nao cung lien quan en hoa hoc chat keo nhnganh cong nghiep cao su, luyen kim, cong nghiep silicat, thuoc da, cong nghiephoa hoc, nhuom, dc pham, thc pham, cong nghiep dau mo,

II.ieu che dung dch keo:1.Nguyen tac ieu che dung dch keo:

+ V he keo co kch thc hat nam trung gian gia kch thc phan t va kchthc cac hat tho hn nen co 2 phng phap ieu che dung dch keo la phngphap phan tan (chia nho cac hat tho hn) va phng phap ngng tu (tap hp cac

phan t, ion hoac cac hat be hn thanh cac hat ln hn).

+ ieu kien e ieu che dung dch keo la tng phan tan phai t tan hoac khongtan trong moi trng phan tan va trong he phai co chat on nh nham khong chocac hat lien ket lai voi nhau thanh hat ln hn, tc la e tranh s keo tu.

2.Cac phng phap ieu che dung dch keo:a.Phng phap phan tan:+ Dung nang lng (c nang, ien nang, sieu am, ) e chia nho cac hat tho hnroi phan bo chung vao moi trng phan tan.

+ Cac hien tng phan tan thng gap trong t nhien va i song:

- Qua trnh tao thanh bui do phong hoa.

- Qua trnh tao thanh nc phu sa do phong hoa va ra troi.

- S xay bot, xay ca phe, s tao thanh sa voi, sa uong,...

+ Cac phng phap phan tan: co nhieu phng phap phan tan nh phan tan bangc hoc (xay, nghien, khuay, lac,...), phan tan bang sieu am, phan tan bang hoquang ien va phan tan nh s keo tano la qua trnh lam tan chat ket tua dos keo tu gay ra (co 4 loai keo tan la keo tan bang cach ra ket tua, keo tan bangcach cho them chat ien li, keo tan bang cach cho them chat hoat ong be mat va



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Chng IX.TNH CHAT ONG HOC PHAN T VA S PHAN TANANH SANG CUA CAC HE PHAN TAN

I.Tnh chat ong hoc phan t cua cac he phan tan:1.Khai niem ve s khuech tan:

La qua trnh lam ong eu nong o phan t, ion hay cac hat keo trong he. o laqua trnh t y xay ra trong he do anh hng cua chuyen ong nhiet. Qua trnh khuechtan la qua trnh bat thuan nghch, no co c khi va ch khi co gradient nong o

(dC

dx0).

2.o ben vng sa lang:+ Tuy thuoc vao kch thc cua hat tng phan tan ma anh hng cua trong trngva s khuech tan manh hn hay yeu hn.

- Nhng he co kch thc hat be th chu anh hng cua trong trng be nhnglai chu anh hng cua s khuech tan manh, nhng he o cac hat phan bo euva khong b sa lang- o la nhng he ben vng sa lang.

- Nhng he phan tan tho co kch thc hat ln th chu anh hng cua trongtrng ln nhng lai chu anh hng cua s khuech tan be va do o, se b salang- o la nhng he khong ben vng sa lang.

- Dung dch keo chiem v tr trung gian gia hai loai he noi tren.+ Co hai trng hp sa lang la:

- Trng hp 1: cac hat sa lang oc lap, khong lien ket lai vi nhau; s sa langxay ra cham. Nhng he o la nhng he ben vng lien ket (t gap trong thc te ).

- Trng hp 2: cac hat lien ket lai vi nhau thanh hat ln hn tng cum 1 (ola s keo tu). Nhng he o la nhng he khong ben vng lien ket (pho bientrong thc te ).

II.S phan tan anh sang:a.Hien tng:

Khi chieu 1 chum anh sang manh qua dung dch keo th thay co 1 dai sang hnhnon m uc - o la hien tng phan tan anh sang cua dung dch keo, hien tng ocon goi la hien tng Tanhan (Tyndahl).

b.Nguyen nhan:Tia sang tren ng i cua no gap nhng hat cua tng phan tan va tuy thuoc

vao he thc gia o dai cua song anh sang va kch thc hat tng phan tan mahien tng co s khac nhau.



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+ Neu kch thc hat ln hn bc song anh sang th anh sang se phan xatren be mat hat di nhng goc xac nh. Hien tng nay quan sat c nhnghe tho he keo nh huyen phu, bui, sng mu, ...

+ Neu kch thc hat be hn th se xay ra s nhieu xa anh sang. Do ket quacua s nhieu xa, tia sang phan tan co ac iem khac vi tia sang phan xa la no toai theo moi hng.

- Neu kch thc hat nho hn nhieu th anh sang phan tan theo cac 0ova180oso vi tia ti la manh hn ca.

- Neu kch thc hat xap x bang th anh sang phan tan theo goc 0o lamanh nhat.

c.Phng trnh Raylay (Rayleigh):+ Phng trnh: Ipt= 24

3 1

2

2

2

12

22

22

4 02n n

n nv I+

. . (IX-1), trong o: n1 va n2 la chiet

suat cua tng phan tan va moi trng phan tan tng ng, la nong o hat, v lathe tch moi hat, la o dai song cua anh sang ti va Iova Iptla cng o cua anhsang ti va anh sang phan tan tng ng.

Phng trnh Raylay ch ap dung c cho he keo kha loang, hat hnh cau, khongdan ien va kch thc hat nho hn 0,1. oi vi cac he keo co kch thc hat lnhn th Iptty le nghch vi co luy tha nho hn 4.

+ T phng trnh Raylay ta rut ra mot vai nhan xet sau ay:

- Khi cac hat co kch thc nhat nh th Iptty le thuan vi nhng khi rat lnth anh sang b phan tan nhieu lan (co s phan tan th cap) va v vay, phngtrnh Raylay phai c bo chnh.

- Iptty le thuan vi v2 va vi hat hnh cau th Iptty le thuan vi r

6. Khi nong otrong lng khong oi, o phan tan cua dung dch keo cang cao (tc la kchthc hat cang nho) th anh sang phan tan cang yeu .

- V Iptty le nghch vi 4 nen khi tia sang co cang nho th cang b phan tan

manh va ngc lai, khi cang ln th cang t b phan tan (chu yeu truyen

thang). ieu nay giai thch mau nc bien buoi tra thng co mau xanh, conbnh minh va hoang hon thng co mau o.

- Trong cac dung dch keo kim loai, anh sang phan tan manh hn trong cac dungdch polimer v ty trong cua kim loai ln hn nhieu so vi moi trng phan tanva do vay, chiet suat ln hn nhieu moi trng phan tan, trong khi o ty trongcua cac polimer khac t moi trng phan tan.

- Anh sang phan tan oi vi dung dch that la rat yeu v phan t co kch thcnho be (v rat be) nen tch so .v2trong phng trnh Raylay khong ang ke. Tuynhien, s phan tan anh sang van co the manh khi chieu vao dung dch that 1

chum anh sang co rat be, nh tia Rnghen chang han.



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CHNG X.S HAP PHU, TNH CHAT IEN CUA CAC HE KEO VAS KEO TU

I.S hap phu:1.Khai niem ve s hap phu:

+ nh ngha s hap phu: la s chat cha cac phan t kh, long hay ran hoa tan lenbe mat phan cach tng. Be mat phan cach tng co the la kh- ran, kh - long, long-long va long- ran.

+ Trong s hap phu, ngi ta phan biet hai loai chat la:

- Chat b hap phu: chat chat cha.

- Vat hap phu : chat b chat cha.

V du : * Qua trnh hap phu cua NO2tren be mat than hoat tnh.

* Qua trnh hap phu cua xa phong tren be mat vai si - dung dch.

* Qua trnh hap phu cua acid acetic tren be mat than hoat tnh - dungdch.

Trong cac v du tren, NO2, xa phong va acid acetic la chat b hap phu va thanhoat tnh, vai si va than hoat tnh la vat hap phu.

+ Ngi ta chia s hap phu thanh 2 loai sau:

- Hap phu vat ly hay hap phu Vandervan: lc hap phu la lc phan t va bao gicung thuan nghch.

- Hap phu hoa hoc: lc hap phu co ban chat hoa hoc va luon luon bat thuannghch.

2.Phng trnh hap phu cua Frendlich (Freundlich):+ Phng trnh hap phu cua Frendlich: = .P(X-1); =.C(X-2), trong o: laai lng hap phu, va la cac hang so, C la nong o chat b hap phu va P la apsuat cua chat b hap phu.

+ Ngi ta co the tm cac hang so trong phng trnh Frendlich bang thc nghiemnh sau:

- T (X-2), ta suy ra: lg= lgC + lg (X-3).

- Bang thc nghiem, ta tm c cac gia tr 1, 2,...ng vi C1, C2,...t o, ta suyra c lg1, lg2,...ng vi lgC1, lgC2,...

- Ve o th bieu dien s phu thuoc cua lgvao lgC co dang nh tren H.X.1.



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- T o th H.X.1, ta suy ra c cac hang so nh sau:

= tg va OB = lg= .OB10

3.S phu thuoc cua vao T:Khi tang nhiet o th s hap phu giam, tc la giam, v s hap phu luon luon

toa nhiet, va ngc lai (xem H.X.2).

4.Phng trnh hap phu cua Langmuya (Langmuir):+ Phng trnh hap phu cua Langmuya:=max.

P

P A+ (X-4); =max.

C

C A+ (X-5),

trong o A vamax la cac hang so.

+ T phng trnh Langmuir, ta suy ra:C

CA

= +

1

max max

. (X-6).

+ Bang thc nghiem, ta xay dng c o thC

C

co dang nh tren H.X.3.

+ T o th, ta suy ra : tg= 1/ max max = cotg va OB= A/ maxA = OB.cotg

5.S hap phu tren ranh gii dung dch - chat kh:a.Sc cang be mat ():+ Lc tac dung len mot n v chieu dai be mat e tach chat ra khoi be mat goi lasc cang be mat, tc la nang lng t do cua 1 n v be mat (yn/cm, erg/cm 2).



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+ Chat long cang phan cc th noi ap cang ln va do o, sc cang be mat cang lnva ngc lai.

V du: .H O C H OH C H2 2 5> > 6 6

b.Chat hoat ong be mat (chat hbm) :Khi hoa tan 1 chat nao o vao chat long th tuy thuoc vao sc cang be mat cua

dung dch (dd) va cua dung moi (dm) ma ngi ta chia chat o ra cac loai chatsau ay:

i. Chat hbm: la chat co kha nang chat cha len lp be mat, ngha la > 0, tcla co s hap phu dng.

Chat hbm phai la chat:

+ Co be hn dm, v the s chat cha no len lp be mat mi t y nhiet ong hoc

va ket qua la ddbe hn dm.

+ Co o tan tng oi be, v neu khong the th no co xu hng ri khoi be mat etan sau vao chat long.

ac iem chat hbm la cau tao phan t gom 2 phan: phan phan cc la nhngnhom chc va phan khong phan cc la nhng goc hyrocarbon.

V du: cac acid beo va muoi cua chung, acid ankylsunfonic, ankylarylsunfonic vamuoi cua chung,...

ii. Chat khong hoat ong be mat (chat khbm):la chat co xu hng rikhoi be mat e tan sau vao chat long, ta co < 0, tc la co s hap phu am.

Nhng chat khbm co tnh chat sau:

+ Co ln hn dm, v the qua trnh ri khoi be mat mi t y nhiet ong hoc, ketqua la ddln hn dm.

+ Co o tan cao, v the chat tan mi t y ri khoi be mat e tan sau vao chat long.

V du: cac chat ien ly nh acid, baz va muoi vo c.

iii.Chat t hoat ong be mat: s co mat cua loai chat nay trong chat long

khong lam thay oi ang ke sc cang be mat cua dung moi.V du: ng saccaroz.

iv.Tom lai:Ta co the da vao s phu thuoc cua ddvao nong o dung dch ephan loai chat hbm, chat khbm va chat t hbm(xem H.X.4).

c.Phng trnh hap phu cua Gipx (Gibbs):+ Phng trnh hap phu cua Gipx: =

C

RT

d

dC.

(X-7), trong o: C la nong o

dung dch, R la hang so kh, T la nhiet o tuyet oi va la sc cang be mat cua

dung dch.+ T phng trnh Gipx, ta nhan thay rang:



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- Neu C tang ma tang, tc la d/dC>0, th 0, ta noi rang nong o chat

tan tren lp be mat ln hn trong dung dch, ta co s hap phu dng.- Neu khong oi theo C th chat tan phan bo eu va khong co s hap phu.

- ai lng -d/dC=G goi la o hbm hay tnh hbm. Ta co: = G.C

RT(X-8).

d.Phng trnh hap phu cua Sitkovxki:+ Khi nong o cua chat hbm be th o-== k.C (X-9).

+ Khi nong o cua chat hbm khong be th =o-=o.B.ln (C

A+ 1) (X-10), trong

o: B la hang so, t phu thuoc vao ban chat cua chat hbm va bang 0,2 20 oC, Ala hang so ac trng cho moi chat hbm, k la hang so, ova la sc cang be matcua dung moi va dung dch tng ng.

+ Phng trnh Sitkovxki ap dung tot cho cac acid beo co so nguyen t carbonkhong qua ln (8 ).

+ Ta co the dung phng trnh Sitkovxki e chuyen phng trnh Gipx thanhphng trnh Langmuya.

Ta se chng minh ieu o nh sau:

T phng trnh: o-=o.Bln (CA

+ 1) )-d= o.Bdln (C A+ =o.B ( )dCA C+

-AC

B

dC

d o

+=

. Thay -AC

B

dC

d o

+=

vao phng trnh Gipx, ta c: =CA

C

RT

Bo

+.

.

at max=RT

Bo

, ta co: = max.

C

A C+, ay la phng trnh Langmuya.

+ Nhan xet:

- A trong phng trnh Sitkovxki cung chnh la A trong phng trnh Langmuya.

- maxphu thuoc vao nhiet o, khi nhiet o tang th maxgiam va do o, giamva ngc lai.

e.Qui tac uclo-Traobe ( Duclaux-Traube):+ Qui tac nay neu len anh hng cua cau tao va kch thc cua phan t chat hbmen s hap phu.

+ Nh a noi tren, chat hbm phan t gom 2 phan:

- Phan phan cc co momen lng cc ln, la nhng nhom chc nh -COOH, -COO-,

-OH, -NH2, -SO4H, -SO4-,..., c k hieu la o.



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- Phan khong phan cc la goc hydrocarbon no hoac khong no hoac thm nhC17H35-, C17H33-, C12H25C6H4-,...., c k hieu la hoac .

+ Chieu dai cua goc hydrocarbon co anh hng ln en o hbm cua chat hbm.

+ uclo-Traobe thay rang: o hbm cua acid hu c no trong nc trong mot dayong ang tang len theo so nguyen t carbon cua goc hydrocarbon, trung bnh motnhom CH2 tang 3,2 lan. Co the phat bieu qui tac nay mot cach khac la khi chieudai cua acid beo tang theo cap so cong th o hbm (-d/dC) tang theo cap sonhan.

+ Nguyen nhan cua s phu thuoc o la: Khi chieu dai mach tang th o tan giamva do o, xu hng chuyen len be mat tang.

+ Qui tac uclo-Traobe con ap dung tot cho cac day ong ang khac cua cac chathbm nh ru, amin,

+ Qui tac uclo-Traobe khong ung cac nhiet o ln hn nhiet o phong vakhong ap dung cho dung moi khac nc.

6.S hap phu tren ranh gii dung dch-vat ran:ay la s hap phu quan trong nhat oi vi hoa hoc chat keo v no gan lien vi

nhieu hien tng va qua trnh xay ra trong cac he keo: s tao thanh, tnh ben vngva s pha huy cac lioson.

Trong s hap phu, ngi ta phan biet s hap phu phan t va s hap phu chatien li.

a.S hap phu phan t:+ Lng chat b hap phu tren 1 gam vat hap phu (mmol/gam) tren be mat vat ran -

dung dch c tnh theo cong thc sau: =C C

mV

C C

mv0 01000

=

. . . (X-11),

trong o: Cova C la nong o ban au va sau khi co can bang hap phu cua dungdch chat b hap phu, m la khoi lng vat hap phu (g), V la the tch dung dch chatb hap phu (lt) va v la the tch dung dch chat b hap phu (ml).

+ S hap phu tren be mat vat ran -dung dch cung tuan theo cac phng trnh hap

phu, thng dung nhat la phng trnh Langmuya va co khi dung phng trnhFrendlich nong o nho.

Nhac lai cac phng trnh hap phu: phng trnh Frendlich: = .C ; phng

trnh Langmuya: =maxC

A C+; phng trnh Gipx: = -

C

RT

d

dC

; phng trnh

Sitkovxki: khi nong o nho:o-=kC va khi nong o khong nho:o-=o

.B.ln(C

A+ 1) .

+ Cac yeu to anh hng en s hap phu:

- Anh hng cua moi trng: Moi trng va chat tan canh tranh nhau trong shap phu nhng cau t nao co sc cang be mat be hn se b hap phu manh hn.



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- Anh hng cua tnh chat vat hap phu: Ban chat va o xop cua vat hap phu coanh hng ln en s hap phu.

* Vat hap phu khong phan cc hap phu chat khong phan cc manh hn va

ngc lai.* Vat hap phu co o xop cang ln (lo xop cang be) se hap phu manh hn va

ngc lai.

- Anh hng cua chat b hap phu:

* Qui tac Rebinia noi rang chat C se b hap phu len be mat phan cachtng A-B neu chat C thoa man ieu kien sau: A < C < B hoac B < C C15H31COOH; C12H25C6H4SO3H >C17H35COOH;C

12H

25C

6H

4SO

3H >C

18H

37SO

3H.

* S hap phu tren ranh gii vat ran -dung dch cung thoa man ve mat nhtnh qui tac uclo-Traobe.

V du: C3H7COOH > C2H5COOH > CH3COOH.

- Anh hng cua nhiet o va thi gian:

* S hap phu trong dung dch cham hn trong tng kh v s khuech tan cuachat trong tng kh nhanh hn trong tng long do o nht cua chat kh behn nhieu o nht cua chat long.

* S hap phu cac phan t ln cong kenh len vat hap phu co lo xop be ratcham. Khoi lng chat b hap phu cang ln th thi gian e at c entrang thai can bang hap phu cang ln.

* Khi tang nhiet o th s hap phu trong dung dch giam do s hap phu toanhiet.

+ Y ngha cua s hap phu trong t nhien va ky thuat:

- Co y ngha ln trong c the sinh vat, ac biet la van e xuc tac men.

- Co y ngha ln trong ky thuat nh tay trang ng bang than, tay trang dau

bang at set, tach cac nguyen to hiem bang hap phu, ...



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b.S hap phu chat ien li:+ Nh ta a biet, chat ien li tren be mat thoang cua dung dch chung b hap phuam, chat ien li la chat khong hbm.

+ Khi co mat trong dung dch mot vat hap phu ran th tren be mat phan cach vatran-dung dch thng co s hap phu dng nhng chat ien li.

+ Ban chat cua vat hap phu co y ngha quyet nh trong s hap phu cac ion.

- Cac ion co kha nang phan cc thng ch b hap phu tren cac be mat co cacphan t phan cc hoac ion.

- Cac ion ngc dau vi ion cua vat hap phu se b hap phu.

+ Ban chat cua chat ien li cung co anh hng ln en s hap phu.

- Cac ion co cunh hoa tr, ion nao co ban knh ln hn se b hap phu manh hn.

V du: Na+< K+< Rb+; Cl-< Br-< NO3-< I-< CNS-.

- Ion co hoa tr cang cao th cang b hap phu manh.

V du: K+< Ca2+< Al3+< Th4+; Cl-< SO4-< PO4

3-.

+ S hap phu chat ien li la s hap phu chon loc.

V du: Tinh the AgI neu trong dung dch co KI va KCl th ion I-se b hap phu lenbe mat AgI tao nen ion quyet nh the hieu cua hat keo AgI (keo am).

+ S hap phu ion co s hap phu trao oi io. o la trao oi gia ion cua lp ien

kep vi ion cua moi trng; ngoai ra con co the xay ra s hap phu ca vi cac iontao nen vat hap phu o khi chung ien li ra. ieu nay thng xay ra oi vi cacnha trao oi ion (trong sac ky trao oi ion vi cac cot trao oi ion cationit vaanionit).

+ac iem cua s hap phu trao oi ion:

- o la s hap phu ac biet, ngha la s hap phu ch xay ra oi vi nhng ionxac nh. Noi cach khac la ban chat cua tng ran va lp ien kep tren be mattng ran cung nh ban chat cua ion b hap phu co anh hng ln en s happhu trao oi.

Trong s hap phu trao oi, ngi ta chia ra vat hap phu acid, baz va lng tnh.

* Vat hap phu acid x s nh mot acid va co kha nang trao oi vi cation cuadung dch, v du nh SiO2(mSiO2.nSiO3

2-.2(n-x)H+.2xH+).

* Vat hap phu baz x s nh mot baz va co kha nang trao oi vi anion cua dungdch, v du nh Fe(OH)3.

* Vat hap phu lng tnh x s nh mot chat lng tnh va co kha nang trao oivi anion hoac cation la tuy thuoc vao ieu kien moi trng, v du nh Al(OH)2SiO3H.

- Khong phai luon luon thuan nghch.



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- Xay ra cham hn nhieu so vi s hap phu phan t.

- Co the lam thay oi pH cua moi trng khi trao oi H+hoac OH-.

V du:

[ ] [ ]

[ ] [ ] ++++

++++

++++

++++

OHNaClVHPClNaOHVHP

ClHNaVHPClNaHVHP

+ Y ngha cua s hap phu trao oi: co y ngha ln trong ky thuat, nong nghiep, hoahoc,...

- Trong nong nghiep: kha nang hap phu cua at va gi nhng ion xac nh trongat.

- Trong ky thuat: ky thuat nhuom, cong nghiep lam mem nc, ...

- Trong hoa hoc: e tach cac chat qu t dung dch rat loang, trong hoa hoc phantch, ...

II.Tnh chat ien cua cac he keo va s keo tu:1.Cau tao cua hat keo:

+ Hat keo gom1 nhan, thng co cau tao tinh the, va lp ien kep bao quanh.Toan bo he thong o goi la mixen hay hat keo.

+ V du:

- V du 1: Keo dng AgI co cau tao nh sau:

- V du 2: Keo am AgI co cau tao nh sau:



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3.S keo tu:a.Khai niem ve s keo tu:+ o ben vng cua 1 he keo tc la kha nang cua no duy tr c trang thai phan

tan khong oi theo thi gian.+ Cac he keo khac vi cac dung dch that cung nh cac dung dch polimer la co bemat rieng ln nen chung la nhng he khong ben vng nhiet ong hoc va do o,khong ben vng tap hp.

+ Chnh v vay ma van e lam cho he keo ben vng la van e quan trong cua hoahoc chat keo va s keo tu la hien tng cung het sc quan trong va ac trng chocac he keo.

+ Tnh khong ben vng cua he keo the hien theo hai cach la:

- So hat giam i do ket qua cua s tai ket tinh, tc la qua trnh ket tinh cac hatln thanh hat ln hn va cac hat nho th b tan dan ra. Nhng trng nay t gapva khong pho bien oi vi cac he keo.

- Cac hat lien ket lai vi nhau thanh nhng tap hp (thanh hat ln hn-o la skeo tu). ay la trng pho bien va co y ngha quan trong trong thc te.

S lien ket cac hat keo lai vi nhau la do ket qua cua s va cham gia cachat nhng khong phai va cham nao cung dan ti hieu qua ma ch co 1 so va chamco hieu qua, phu thuoc vao tnh chat be mat cua cac hat keo.

Khi a vao he keo1 lng nho chat co kha nang hap phu th nhng tnhchat be mat cua hat keo b thay oi manh va do o, ket qua cua s va cham cung sethay oi.

Khi hau het cac va cham eu dan en hieu qua, ta co s keo tu nhanh vakhi khong phai nh vay, ta co s keo tu cham hoac he keo ben vng.

+ Co hai lc xuat hien gia cac hat keo la:

- Lc hut phan t Vandecvan.

- Lc ay tnh ien do cac hat keo mang ien cung dau.

Tuy thuoc vao tng quan gia 2 lc noi tren ma he keo ben vng hay bkeo tu. Khi lc hut thang lc ay th he keo b keo tu va ngc lai, khi lc hut thualc ay th he keo ben vng.

b.S keo tu bang chat ien li:+ Hau het cac chat ien li eu co kha nang gay keo tu he keo.

+ Kha nang gay keo tu cua chat ien li c ac trng bang nong o toi thieu cuano can e gay keo tu mot he keo nhat nh vi mot toc o nhat nh -o la ngngkeo tu va c bieu th bang n v mmol/lt hoac mlg/lt, k hieu ngng keo tula .



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+ Gia tr phu thuoc vao nong o cua dung dch keo; do o, gia tr cua cac tacgia khac nhau la khac nhau.

+ Quy tac Sunde-Hacdi (Schoulze-Hardi):

- Ch co ion ngc dau vi hat keo mi co kha nang gay keo tu he keo.- Cac ion co hoa tr cang cang cao th kha nang gay keo tu cang ln, cang nho.

+ Kha nang gay keo tu cua cac ion cung hoa tr tang khi ban knh ion tang oi vication va giam oi vi anion.

V du: oi vi keo am th Li+< Na+< K+va oi vi keo dng th Cl-> Br-> I-.

+ Cac ion hu c co kha nang gay keo tu manh hn nhieu cac ion vo c cung hoatr v cac ion hu c co kha nang hap phu manh hn nhieu. Cac ion hu c cunghoa tr, ion nao co kha nang hap phu manh hn se co kha nang gay keo tu manh

hn .V du: C17H35COO

- >C15H31COO-; C12H25C6H4SO3

- >C12H25SO4-; C17H35COO

- >Cl-; C16H33NH3

+>Na+.

+ Ngi ta thay rang s keo tu bat au xay ra the de ta ti han la khoang 30 mv(khong xet dau).

+ S phu thuoc cua toc to keo tu (v) vao nong o chat ien li cho vao (C) cbieu bien bang o th H.X.9.

Tren o th H.X.9, vung 1 la vu

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