Ch Ng 1 Dd i n Ly

25/01/2015

1

GV: TS MAI TH HI H

Chng 1

DUNG DCH CC CHT IN LY :

CU TRC & TNH CHT

Thnh phn ca dung dch in ly

Cht tan : hp cht lin kt ion/cng ha tr c cc

Dung mi : hp cht phn cc

Cht tan phn ly mt phn/hon ton thnh ion vi in ly

Cc ht trong dd in ly gm :

ion cht tan, phn t cht tan cha b phn ly, phn t dung mi

25-Jan-15 TS. MTH H 2

+ _ _ +

Lc tng tc tnh in Coulomb : ion-ion, ion-dung mi, dung mi-dung mi

Cc phn t u mang in tch

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Cu trc ca dung dch in ly

Lc tng tc tnh in Coulomb gia cc tiu phn lm cho :

Cc ion phn b c trt t (khng chuyn ng t do nh trng thi kh).

Chuyn ng ca cc ion u chu nh hng bi in trng ca cc ion khc

xung quanh.

Mi ion c bao quanh bi mt s phn t dung mi : s solvat ha

Khi cc ion gn nhau (trong dung dch nng ln) : c s lin hp ion

(c tha nhn bng pp ph cng hng t ht nhn/electron)


Tng tc ion dung mi : s solvat ha


Phn t H2O gn ion lin kt

tnh in cht vi ion

Lp v hydrat s cp

H2O trong lp v hidrat mt kh

nng quay

Hng s in mi ca nc

gim mnh khu vc gn ion

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Tng tc ion ion : s lin hp ion

Khi nng ion ln : cc cation v anion

tng tc tnh in mnh to thnh cp 2, 3

hay nhiu hn ion : C+A-C+, A-C+C+A-.

S to cp ion xy ra d dng hn trong dung

mi c hng s in mi thp (

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Mu dd in ly - Thuyt Debye Huckel (1923)

Cc tiu phn trong dd in ly c phn b :

c trt t do lc tng tc tnh in gia chng

hn lon do chuyn ng nhit

M hnh bu kh quyn ion :

Mi ion l 1 trung tm, c bao quanh bi 1 kh quyn gm cc ion tch

in tri du vi s lng nhiu hn ion cng du.


Chn ion dng bt k lm trung tm : in tch zke

ko : in th to bi ion trung tm

a : in th ca bu kh quyn ion

k : in th ti mt im cch ion trung tm khong r

k = ko + a

25-Jan-15

Mu dd in ly - Thuyt Debye Huckel

*Gi thit : Dd long c th :

B qua kch thc ion Th nng tnh in ziek

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Mu dd in ly - Thuyt Debye Huckel


2 = -

in th ti mt im mt in tch ti im theo pt Poisson :

: ton t Laplace

: hng s in mi ca dung dch

Nghim tng qut ca pt vi phn :

k1, k2 : hng s tch phn, c xc nh da vo cc iu kin bin :

r , th k 0 : k2 = 0

r 0, th k k ko : in th gy bi ion trung tm =

zke

4r

er k1 = zke

4 =

zke

4

Thuyt Debye Huckel


a (r0) = - Zie

.1/

LD = -1 c coi l bn knh hiu dng ca bu kh quyn ion

in th k ti mt im cch ion trung tm khong r :

Lc ion I :

Dung mi nc 25oC :

(h SI)

(I: mol/dm3, LD : nm)

k = ko + a

ci : nng th tch

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1. Tm lc ion ca dung dch:

a. cha Na2SO4 0,08 mol v Cr2(SO4)3 0,02 mol trong 1000 g nc.

b. cha MgSO4 0,01 mol, NaCl 0,005 mol v MgCl2 0,001 mol trong 1000 g

nc.

2. Tm kch thc hiu dng ca lp kh quyn ion 25oC trong dung dch cht

in ly 1-1 c nng 0,1M. Cho hng s in mi ca nc bng 78,6.


Hot - H s hot


Ha th ca ion k trong dd l tng : k,id = o

k,id + RTlnck

Cc phng trnh m t h l tng c th c dng cho h thc t bng

cch thay nng c bng hot a.

Ha th ca ion k trong dd thc : k = o

k + RTlnak

Lin h gia hot & nng : ak = k . Ck

k : h s hot

Hot & h s hot thang nng : mol/L, molan, lg/L

Dd long ca CL yu : a C : 1

Mc lch ca h khi trng thi l tng lch ca khi gi tr 1

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Hot & H s hot trung bnh

M+A- + MZ+ + - A

Z-

Nng molan : m m+ =+ m m- = -m

Hot /H s hot : a / a+ / + a- / -

a = m a+ = + m+ a- = -m-

Hot /H s hot trung bnh ca cc ion : a /

Ha th : =o + RTlna + =o

+ + RTlna+ -= o

- + RTlna-

Ha th ca cht tan = ha th cc ion

= + + + - - RTlna = + RTlna+ + - RTlna- (o

= + o

+ + - o

-) a = a++ a-

-

Hot ca cht in ly : a = a++ a-

- = a = + + -

Hot trung bnh ca cc ion : a = (a++ a-

-) 1/ = a1/


Hot & H s hot trung bnh

Hot trung bnh ca cc ion :

a = (a++ a-

-) 1/

a = [(+ m+)+( - m- )

-]1/ = (++-

-) 1/ (m+ +m-

-)1/

H s hot trung bnh ca ion :

= (++-

-) 1/

Nng trung bnh ca ion :

m = (m+ +m-

-)1/ = [(+m)+(-m)

-]1/

= (+ +-

-)1/ m

= Pm vi P = (+ +-

-)1/

a = m = Pm


CL 1-1 : NaCl 1-2, 2-1 : K2SO4 , CaCl2 1-3 : AlCl3 2-3 : Ca3(PO4)2

P = 1 P =

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3. Dung dch Ca(NO3)2 nng molan 0,2 c h s hot ion trung

bnh l 0,426. Tm nng ion trung bnh, hot ion trung bnh v

hot ca mui.

4. Xc nh hot v hot trung bnh ca ZnSO4 trong dung dch

0,1 m nu = 0,148.


25-Jan-15 TS. MTH H

+

+ _

_ +

+

_ _

nng C

+ _

dd l tng

dd thc

G

Gid

trng thi chun

H s hot

Ha th ca ion k trong dd thc : k = o

k + RTlnck + RTlnk

k o

k = RTlnck + RTlnk

k = k,id + RTlnk = k,id + kE

Phn hiu chnh do tnh cht thc

k

k,id

GE = G - Gid

kE

nng C trng thi chun

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+

+

_

_ +

+

_ _

nng c (dd thc) : Trng thi chun (1 mol/dm3)

long v cng (dd l tng)

Cng phng in W1

Khng c cng in

Cng tch in W2

k

zke

Cng phng in ca 1 ion W1

in th ti khong cch r :

Cng Wk

+ _

H s hot theo thuyt Debye Huckel

k


Cng tch in ca 1 ion W2 :

Cng in tng Wk cho ion k :

Cng in tng Wel cho tt c cc ion trong th tch dung dch V :

S ion Ni = s mol ni . NA


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25-Jan-15

TS. MTH H

19

Gi s th tch V khng ph thuc ni, tc coi ion

nh cht im, khng c kch thc

log k = Azk

Nghim ng cho cht in ly 1+-1- c lc ion di 10-2 mol/dm3

Nc 25oC :


log = 0,509z+

nh lut gii hn Debye-Huckel (Pt gn ng bc 1)


Pt gn ng bc 2 ca D-H : C tnh n kch thc ring ca ion

Cc ion ch n gn nhau mt khong gn nht l a (tnh t tm ion)


a : ng knh hiu dng ca ion, a 0,3-0,5 nm

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Pt gn ng bc 2 ca D-H :


B = (8e2N)1/2

(103kT)1/2

lg = - |Z+.Z-|A

1 + a.B

Pt bc 2 nghim ng cho dd nng long 0,01 - 0,1 mol/lt, CL 1+-1-

ToC A B

0 88,15 0,488 0,325.108

15 82,23 0,5 0,328.108

25 78,54 0,509 0,330.108

30 78,76 0,514 0,331.108

40 73,35 0,524 0,333.108

50 70,1 0,535 0,335.108

Dd nc to phng :

B = 0,330.108 a.B = 1

lg = - |Z+.Z-|A

1 +

a 3-4.10-8 cm

A, B hng s in mi, nhit .

a : ng knh hiu dng ca ion

Vi nc 25oC :

a 0,3-0,5 nm Ba = 1


Pt gn ng bc 3 ca D-H :

Khi dung dch c nng CL cao (lc ion c th t n n v) : > 1

dd c : s y gia cc ion chim u th hn so vi s ht gia cc ion

s tng hot so vi nng , lm cho > 1


lg

= - Az+z-

1 + Ba

+ CI Vi C : hng s kinh nghim

Lu :

S ht gia cc ion s gim hot so vi nng

S y gia cc ion s tng hot so vi nng

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Lin h h s hot ion - nng NaCl/H2O


Quy lut thc nghim :

khi nng (mol/L) tng, qua mt cc tiu

Gii thch :

* Dd long (lc ht gia cc ion >> lc y)

khi

tng, lc ht tng gim

* Dd c (lc ht gia cc ion

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5. Dung dch nc ca BaCl2 0,002 m 298 K. Da vo nh lut gii hn ca

D-H, tm h s hot ca ion trong dd v h s hot trung bnh ca ion.

6. Hy tnh h s hot ca ion CrO42- v hot trung bnh ca Ag2CrO4

trong dd nc 25oC khi ha tan 8.10-5 mol/L (in ly hon ton) v c thm

cc cht in ly khc sao cho lc ion bng 0,01.

7. tan ca Tali iodat TlIO3 trong nc c cha KCl 25oC cho trong bng.

a. Tm tch s tan ca TlIO3

b. H s hot ion trung bnh KCl 0,02 mol/lt

c. Hng s A trong pt gii hn ca D-H


[KCl] mol/lt 0.005 0.01 0.02 0.05

S mol/lt 0.00193 0.00200 0.00210 0.00232

Acid, baz, mui phn ly thnh ion khi ha tan trong nc :

M+A- + MZ+ + - A

Z-

Ban u ck in ly ck c+ = ck+ c- = ck- Sau p cn = ck ck c+ = ck+ c- = ck-

ck : nng ban u (mol/th tch)

j : ion j sinh ra do s in ly cht k ban u

cj : nng th tch ca ion j (thng dng mol/cm3)

: in ly ca cht in ly

k : tng s ion do 1 phn t ban u in ly ra : k = - + +

zk : s in tch ca cht in ly : zk = + z+ = -z

-

Dung dch trung ha in nn : (+) cjzj = () cjzj


c : nng tng cng ca tt c cc cht tan trong dung dch : c = cn + c+ + c- = [1 + (k 1)]ck

dn in ca dung dch in ly

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Tc chuyn ng ca ion vj :

Mi ion j s mang in tch zjF (tnh trn 1 mol ion).

Di in trng E (V/cm) : ion j in di vi tc trung bnh vj

vj ph thuc :

- lc ko ca in trng p vo : fj = zjFE

- lc hm do nht ca dung dch : f= (6r) vj = vj

Gi tr vj t c khi 2 lc ny cn bng nhau : zjFE = vj

1

vj = zjFE

Linh (tc tuyt i) ca ion uj

1

uj = zjF (cm2/V.s)

vj E

= zjF

6r Hay uj =

- : nht ca dd

-r : bn knh hiu dng ion

(c bao gm lp hydrat)

uj = tc ca ion di in trng 1 V/cm

8. ng thy tinh cha dung dch NaCl c gn 2 in cc cch nhau 1,53 cm.

Th 12 V c p vo 2 in cc. Sau 5 pht, Na di chuyn c 1,2 cm.

Tm tc tuyt i ca ion.

9. Cho linh ca ion Li+ l 4.10-4 cm2/Vs. Tm thi gian ion dch chuyn t

in cc ny sang in cc kia nu hiu th 10 V c t vo 2 in cc

cch nhau 1 cm.


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Mt dng ion Jj :

Jj = s mol ion j in di qua 1 n v tit din trong 1 n v thi gian

Ion j c nng th tch cj (mol/cm3) & tc chuyn ng vj (cm/s)

Trong 1 v thi gian, ion j i c vj cm

tt c cc ion nm trong th tch vj s i qua 1 v tit din :

Mt dng in ti bi ion j :

Mt dng in : ij = JjzjF = zjFcjujE

Mt dng tng : i = ij = FEzjcjuj

Mt dng in trng, in tch, linh v nng th tch ca tt c

cc ion.


Jj = s mol ion trong th tch vj = cj vj = cjujE


Mt dng in theo nh lut Ohm :

i t l vi cng in trng :

i = E

bn cht vt liu, nhit

kch thc v dng hnh hc vt liu


dn in ring (S.cm-1) :

l dn ca khi dung dch 1 cm3 t gia 2 in cc din tch 1 cm2, cch

nhau 1 cm

l mt dng in in trng 1 V/cm

= 1

R ()

L (cm)

S (cm2) =

K(cm-1)

R () 1

= S (siemens) = -1

i : mt dng (A/cm2)

: dn in ring (S/cm)

E : cng in trng (V/cm)

: in tr sut

R : in tr

K : hng s bnh (cm-1)

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dn in ring ca dung dch (S.cm-1) :

Mt dng : i = FEzjcjuj

dn in ring ca dung dch = mt dng in in trng 1 V/cm


in tch, nng & linh u ca tt c cc loi ion.

= Fzjcjuj

dn in ring ca dd cht tan nng ban u ck & in ly :

= F (z+c+u+ + z-c-u-) = F [z+(ck+)u+ + z-(ck- )u-]

= F ck ( z++u+ + z--u-) = Fzkck (u+ + u-)

dn in ring ca tng ion : j = Fzjcjuj



dn in ng lng (S.cm2/lg) : dn ca khi dung dch cha 1

ng lng gam cht lg = M(g/mol)/Z (in ha tr)

S lg = m/(M/Z )= s mol. Z

C (lg/L) = C (mol/L) . Z

= .1000

C (lg/L)

= .1000

C (mol/L) = . Z

= F(u+ + u-) = ( + + -) ng lng ca cht trong p ha tan :

= Mj/zj hay Mk/zk s lg = z.s mol

dn in mol ca dung dch :

dn in mol (S.cm2/mol) : l dn ca khi dung dch cha 1 mol cht

dn in mol ca ion j :

= Fzk (u+ + u-) =

ck (mol/cm3)

= F( z++u+ + z--u-) = ( ++ + --)

j = Fzjuj = j

cj (mol/cm3)

j = Fuj = j

cj (lg/cm3)

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dn in gii hn ca dung dch in ly


j = Fuj j, uj : linh ion

= (+ + -)

pha long v cng C 0 : = 1

Linh ca cht in ly v ca cc ion j t gi tr ln nht, gi l gi tr

gii hn hay u

L Kohlrausch 2 : = + + -

Khi dd v cng long, cc ion chuyn ng c lp vi nhau, nn dn in

ng lng gii hn (linh ) ca cht in ly bng tng dn in

ng lng gii hn (linh ) ca cc ion.

Theo Arrhenius : CL yu : Khi C 0 th = 1 : =

=

Bng gi tr dn & linh ion gii hn


Cc gi tr c ngoi suy n long v cng.

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dn in gii hn ca dung dch in ly


H+ (aq), OH- (aq) : Linh rt ln so vi cc ion khc.

Theo c ch Grotthus : s nhy ca H+ thng qua phn t H2O

O H

H

H +

O H

H

O

H

O

H

H O

H

H -

Tm tt cc loi dn in

j = Fzjcjuj = Fzkck (u+ + u-) = + + -

j = Fzjuj = Fzk (u+ + u-) = ( ++ + --)

j = Fuj = F (u+ + u-) = ( + + -)

= + + -

= /


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10. in tr ca dd KNO3 0,01N c o bng 423 trong bnh o c hng s

bnh l 0,5 cm-1. Tm dn in ring, ng lng, in ly biu kin nu

linh gii hn ca ion K+ v NO3- l 64,5 v 61,6 -1.cm2.lg-1 .

11. Hy tnh dn in gii hn ( dn in v cng long) ca AgIO3

298K bit dn in ng lng gii hn ca NaIO3, CH3COONa, CH3COOAg

298K ln lt l 9,11; 9,10; 10,28 cm2/ohm.lg

12. Tm cho


[KCl] mol/L 0.0005 0.001 0.002 0.005 0.01

(-1.cm2.lg-1) 25oC

124.50 123.74 122.70 120.65 118.51

S ph thuc linh ion ( dn ng lng) - nng

S ph thuc ca dn in ng lng

vo (nng cht in ly)1/2 :

* Cht in ly mnh :

C tng : gim lc u gim nhanh, sau gim chm.

Dd long CL mnh : pt thc nghim Kohlrausch 1 :

= A

A : hng s kinh nghim; C = lg/L

* Cht in ly yu :

C tng : gim lc u gim rt nhanh,

sau gim chm


Ph thuc dn in

ng lng nng

ng lng : - c1/2

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S ph thuc linh ion ( dn ng lng) - nng

S gim ca linh ion theo s tng ln ca nng l do s tn ti ca kh

quyn ion :

Hiu ng in di

Hiu ng bt i xng

Ion chuyn ng kh quyn ion tr nn bt i xng vi mt pha sau

ion ln hn : to nn in trng nh ngc chiu vi in trng ngoi

km hm chuyn ng


Di in trng :

Ion v kh quyn chuyn ng ngc chiu

(do in tch tri du)

lc ma st lm gim tc

Ion Kh quyn

V hydrat V hydrat

Nng tng mt ca kh quyn tng cc h cng ln linh ion gim

S ph thuc dn in ring vo nng


* Dd cht in ly mnh (=1) :

ck tng : s lng ion tng, linh ion gim

s tng ca theo ck tr nn chm hn

* Dd cht in ly yu :

ck tng : linh gim + in ly gim

s tng ca theo ck cng tr nn rt

chm so vi TH CL mnh.

* Trong 1 s trng hp, th dn

nng i qua 1 cc i.

Lin h dn in ring 25oC

vi nng (dung mi nc) :

(1) H2SO4; (2) KOH;

(3) NH4Cl; (4) NaNO3

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o dn in bng cu Wheatstone


S : ngun in dng xoay chiu nh, tn s ln

R1 : in tr bnh cha dung dch cn o

R2 : in tr bit trc

BD : dy dn c t s in tr ca 2 on dy

BC, CD bng t s chiu di L1 v L2

C : con chy, dch chuyn v tr trn dy

thay i ln in tr ng vi L1 v L2

A

Cu cn bng : dng i qua G = 0

R1

R2 =

L1

L2

I1R1 = I2.L1

I1R2 = I2.L2 B

C D

S

= K(cm-1)

R1 ()

Hng s bnh K : xc nh nh

dung dch in ly chun (KCl)

bit dn in ring


13. Bnh o dn in c chun bi dung dch KCl 0,02 N c dn

in ring l 0,002768 ohm-1.cm-1. in tr o c 25oC l 457,3 ohm.

Bnh c s dng o in tr ca 1 lt dung dch cha 0,555 g CaCl2 vi

gi tr o c l 1050 ohm. Tm hng s bnh, dn in ring v ng

lng ca dung dch CaCl2 .

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ng dng ca php o dn in

Tm tan ca mui t tan :

Dung dch bo ha mui c :

tan S (lg/L) & dn in (S/cm)

S rt nh dd long : =


= . 1000

S (lg/L) S =

.1000

.1000

14. 25oC, ngi ta o c dn in ring ca dung dch AgCl bo ha

v ca nc l 2,68.10-6 v 0,86.10-6 -1.cm-1. Tm tan ca AgCl trong nc

25oC. Cho dn in ng lng gii hn ca dung dch AgNO3, HCl v

HNO3 25oC ln lt l 133; 426; 421 -1.lg-1.cm2


Chun axit mnh (HCl) : bng kim (NaOH)

im a : H+, Cl-

Thm NaOH : H+ gim, Na+ c linh km H+

im b : im tng ng : HCl p ht : Na+, Cl-

Thm NaOH : thm ion Na+, OH-

dn in th tch NaOH

a

b c

b

VNaOH

H+

ng dng ca php o dn in

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S vn ti


S vn ti ca ion j = phn in lng ti bi ion j :

t+ + t- = 1 t+= i+ i

= u+

u+ + u- =

+

+ + -

Dung dch c 1 cht in ly :

t- = i- i

= u-

u+ + u- =

-

+ + -

tj = ij i

= zjcjuj

zjcjuj

15. Linh ca H+, Cl- v Na+ trong nc 25oC ln lt l 3,623.10-3; 7,91.10-4

v 5,19.10-4 cm2/Vs.

a. Tnh s ti ca H+ trong dung dch HCl 10-3 M.

b. Thm NaCl vo dung dch trn to nng NaCl 1 M (nng HCl xem nh

khng i). Tnh s ti ca H+

Xc nh s vn ti - Phng php Hittorf


Cho 1 Faraday in lng i qua dung dch th :

1 ng lng cht c gii phng trn mi in cc (do p in cc)

t+ : phn in lng ti bi H+

t- : phn in lng ti bi Cl-

1H+ : 1 lg H+ do gii phng trn cathode

+ t+ H+ : t+ lg H+ chuyn n t anode

t- Cl- : t- lg Cl- chuyn i sang anode

(1 t+)H+ t- Cl

- = t- H+ t- Cl- = t- HCl

(1 t-)Cl- t+ H

+ = t+ Cl- t+ H+ = t+ HCl

S lg gim khu cathode :

Bin i lng cht khu cathode :

S lg gim khu anode :

Cathode (-) Anode (+)

1H+ + e H2

+ t+ H+

t- Cl-

1Cl- e Cl2

t+ H+

+ t- Cl-

Khu anode Khu cathode

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Xc nh s vn ti - Phng php Hittorf


na nc

= t+ t-

S ng lng cht c gii phng trn mi in cc (p in cc)

S lg gim khu cathode :

q F

n =

q F

nc = t-

S lg gim khu anode :

q F

na = t+

na

na + nc t+ =

Ca

Ca + Cc =

nc

na + nc t- =

Cc

Ca + Cc =

(Nu th tch dd 2 khu nh nhau :

Va = Vc = V)

1 Faraday in lng S lg gim khu cathode t- HCl

q in lng s lg gim khu cathode nc

16. in phn vi in cc graphit dung dch CuCl2 26,9 g/L. Khi kt thc trong

0,5 l dd khu anode c 4,75 g Cu v 0,5 l dd khu cathode c 3,95 g Cu. Tm tCu2+ v

tCl-

Cathode (-) : Cu2+ + 2e Cu -1Cu + t+Cu t-Cl = -t-CuCl2

Anode (+) : Cl- - e1/2 Cl2 -1Cl + t-Cl t+Cu = -t+CuCl2


mCuCl2 trong 0,5l = 26,9:2 =13,45g

mCuCl2/anode = 4,75/63,54.134,54=10,0576g

mCuCl2/cathode = 3,95/63,54.134,54=8,3637g

mc=5,0863 g

ma=3,3924 g

t+ = 0,3972

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17. in phn dd AgNO3 vi in cc bng Ag. Trong khu anode, lng AgNO3

trc v sau in phn l 0,2278 g v 0,2818 g. C 0,0194 g Cu bm vo cathode

ca coulomb k Cu mc ni tip bnh in phn. Tm s ti ca Ag+ v NO3-

Anode (+) : Ag-eAg+ : +1Ag+ - t+Ag+ + t-NO3 = + t-AgNO3

Ti anode ha tan : tng t- lg AgNO3

q = 0,0194/(MCu = 63,54) *2 = 0,0006106 mol electron = = 0,0006106 F

S lg AgNO3 tng anode = (0,2818-0,2278)/170=0,0003176

t- = 0,0003176 F/ 0,0006106 F = 0,52

Xc nh s vn ti - Pp ranh gii di ng


+

_

MA

MA

a b

a' b' uM

uM

h

Dd MA tip xc vi dd MA ti v tr ab, tit din tip xc S.

ab : ng ngn cch gia 2 dung dch

Linh ion M > M

Cho in lng q=It qua h :

Cation di chuyn v cc m vi tc M > M

mng ab chuyn n v tr ab

S lg M+ chuyn t ab n ab : C (lg/th tch)Sh

Phn in lng ti bi Mz+ :

zFC(lg/th tch)Sh

q t+ =

25/01/2015

26

18. Trong ng hnh tr ng knh 8 mm, ngi ta 2 dung dch HCl 0,01

M v NaCl sao cho gia 2 dung dch c 1 ranh gii r rt. Khi cho dng in

5 mA i qua th ranh gii di chuyn vi tc 0,085 mm/giy. Tm s ti ca

ion H+.


zFC(lg/L)Sh

q t+ =

Z=1

F=96500

C=0,01 lg/L

S=3,14.0,042dm2

h=0,085.10-2 dm

q=5 mA.1s=5.10-3 A

t+=0,824

19. dn in mol gii hn 25oC ca dung dch nc ca NaI, NaCH3COO, Mg(CH3COO)2 ln lt l : 126,9;

91,0; 187,8 S.cm2/mol. Tm dn in mol gii hn 25oC ca MgI2.

20. Hng s phn ly Kc ca axit C3H7COOH l 1,54.10-5. Tm phn ly ca axit ny pha long V=1/C= 1024

lt/mol. Nu dn in mol gii hn ca dd axit l 350 S.cm2/mol, tm dn in mol ca dung dch axit

pha long trn.

21. Hy tnh phn ly v tch s ion ca nc 25C, bit dn in ring ca nc tinh khit 25oC bng

5,5.10-8 om-1.cm-1. dn in ng lng gii hn ca cc ion H+, OH- l 349,8 v 198,0 cm2/lg.om. Khi

lng ring ca nc 1g/mL.

22. 25oC dn in ng lng gii hn ca NaCH3COO l 91 -1.cm2.lg-1. S ti ca anion l 0,43. dn

in ng lng gii hn ca KCl l 149,8 -1.cm2.lg-1 . S ti ca K+ l 0,49. Tm dn in ng lng

gii hn ca KCH3COO.

23. 25oC dn in ring ca dung dch BaCl2 0,02N l 0,002382 -1.cm-1. S ti ca Ba2+ trong dung dch ny

l 0,4375. Tm tc tuyt i ca ion Ba2+ v Cl-.

24. Cho dng in cng 5,21 mA chy qua ng ng dung dch KCl 0,1 M trong 67 pht, ranh gii dch

chuyn c 4,64 cm. ng c tit din 0,23 cm2. Tm s ti ca K+ v Cl-.

25. Trong ng hnh tr ng knh 8 mm 2 dung dch HCl 0,01 M v NaCl sao cho gia 2 dung dch c 1 ranh

gii r rt. Khi cho dng in 5 mA i qua th ranh gii di chuyn vi tc 0,085 mm/giy. Tm s ti ion H+.

26. Dung dch cht in ly mnh AB c in phn trong bnh Hittorf vi dng 0,1 A trong 9650 giy. P trn

cc in cc AA+ + e v A+ + e A. Dung dch c nng ban u 0,1 mol AB trong 1 kg nc. Sau in phn

trong khu vc anode dung dch gm 100 g H2O v 0,0165 mol AB. Tm s vn chuyn ca ion A+.

27. in phn dung dch cha 14,055 g AgNO3 trong 1000 g nc bng cc in cc Ag. Khi kt thc c 0,1020 g

bc thot ra trn cathode, khu anode c 0,4109 g bc trong 40 g nc. Tm s ti ca ion bc v nitrat.


25/01/2015

27

Hng dn gii BT 5. J=0,006, lg+ = -0,509.2

2.0,0061/2 , + = 0,695

lg = |Z+ . Z-|A

= - 2.[1/2(0,002.4 + 0,004.1) ] 1/2.0,509

= 0,834

6. lg- = -0.509.4.0,1=-0,2036 -=0,625

lg = -0.509.1.2.0,1=-0,1018 =0,791

a = P.m. = 41/3 . 8.10-5.0.791=10-4 ionmol/L

7. T= aTl+aIO3-= [Tl+].[IO3

-].Tl+. IO3-=S2 .

2

lgT = 2lg + 2lgS

Pt gn ng bc 1 : lg = -A

lgT = -2A

+ 2lgS

lgS = A

+ 1/2lgT

y = x + 1/2lgT

x = 0 y = 1/2lgT = -2,7594

T = 3,028.10-6


y = 0.547x - 2.7594

-2.72

-2.71

-2.7

-2.69

-2.68

-2.67

-2.66

-2.65

-2.64

-2.63

0 0.05 0.1 0.15 0.2 0.25

lgS

Sqrt(I)

[KCl] 0.005 0.01 0.02 0.05

S 0.00193 0.002 0.0021 0.00232

I 0.00693 0.012 0.0221 0.05232

sqrtI 0.083247 0.109545 0.148661 0.228736

lgS -2.71444 -2.69897 -2.67778 -2.63451

8. v=1,2/300=0,004 cm/s

u=v/E=0,004/(12/1,53)=5,1.e-4

10. =K/R=0,5/423

= /(0,01.10-3) lg/cm3

12. C = 0 = = 126.4

19. MgI2=Mg(CH3COO)2 2NaCH3COO + 2NaI = 259,6

20. Kc=2/V(1- ) = 0,1179

= / = 41,3

TS. MTH H 57

y = -77.231x + 126.18 R = 0.9996

118

119

120

121

122

123

124

125

0 0.02 0.04 0.06 0.08 0.1 0.12

d

n

in

n

g l

ng

C1/2

25/01/2015

28

21. [H2O] = 1/18/1mL = 0,055 mol/mL = 0,055 lg/cm3

=5,5.10-8/0,055=10-6 = 349,8+198=547,8 = / =1,82.10-9 Kw=[H

+][OH-]= 2C2=10-14

22. t- = - / - = 0,43.91 =39,1

23. = 0,002382.1000/0,02=119,1 -1.cm2.lg-1

t+ = +/ + = 0,4375.119,1= 52,106 -1.cm2.lg-1

u+ = +/F = 5,4.10-4 -1.cm2.lg-1/A.s2 = cm2/s.Volt (Ampe=Volt/ )

24. q=5,21mA.67phut=5,21.10-3.67.60 giy =

t+ = 4,64 cm . 0,23cm2 .10-3. 0,1mol/dm3. F / q = 0,4917

25. t+ = (0,085mm..42mm2. 10-6)0,01mol/dm3 .F/ 5mA.10-3.1 giy=0,824

26. Anode : +1A t+A + t-B = t-AB

S lg tng anode = 0,0165 - 0,01=0,0065 lg t- = 0,0065/(0,1.9650/96500)= 0,65 t+=0,35

27. Anode (+) : Ag Ag+ + e 1Ag -t+Ag +t-NO3 = +t-AgNO3

Cathode (-) : Ag+ + e Ag -1Ag +t+Ag -t-NO3 = -t-AgNO3

B : 0,5622 g AgNO3/40g nc = 3,307.10-3 mol Ag/40g nc

Sau p anode : 3,805.10-3 mol Ag/40g nc

q= 0,1020/108 mol e = F. 0,1020/108

1 F thm t- lg AgNO3 hay t- mol AgNO3

q F thm (3,805-3,307).10-3 mol

t- = 0,527

TS. MTH H 58

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