Dien_HH_SV_

1DUNG DCH iN LY: TNH CHT V S CHUYN VN

iN TCH

Chng 5

(Bi ging tm tt) Ni dung1. Gii thiu

2. Tnh cht nhit ng

3. nh lut gii hn Debye-Huckel

4. S dn in

5. S ti

6. Phng php o dn in & ng dng

1. Gii thiu

Cht in lyElectrolyte

Cht in ly (cht in phn): l cccht c th to ra cc dung dch ion vhn hp nng chy c cha cc ion.

2Dung dch cht in lyElectrolyte solutions

L cc dung dch c tnh cht:

ng nht trong th tch

c thnh phn thay i lin tc trongmt gii hn

c kh nng cho dng in i qua nhs chuyn vn in tch ca cc ion.

S in lyElectro- dissociation (dissociation)

l s phn ly ca cc cht in ly trongdung dch.

l mt qu trnh thun nghch

M+A- +Mz+ + -A

z-

Hng s in ly KDDissociation constant

M+A- +Mz+ + -A

z-

Khi cn bng:

AMD n

)n.()n(K

n: nng mol, ion-mol

phn ly Percent dissociation

l s phn phn t phn ly so vi sphn t ho tan trong dung dch ban u.

KD= f()=?

3 phn ly Percent dissociation

)().(

)1(

.nK

)()1(0

D

Khi + = - = 1

1

.nK

20

D n0 = s mol cht in ly (ban u)

H s Van tHoff iVan tHoff factor

l t s gia s phn t sau phn ly (ion + phn t) so vi s phn t trc khi phnly (s phn t ho tan)


0

0000

n

.n..n.).nn(i

i = 1 + (-1).1

1i

t : = + + -

Dung dch long c i 14

Cht in ly yu: c rt nh, 0;

Cht in ly mnh: 1

V d: Cc mui tan, cc acid. base v c


4Tnh cht ca DD CL

ng nht v tnh cht ho l mi imtrong th tch

Thnh phn c th thay i lin tc trongmt gii hn

Tng im si

Gim im kt tinh

Tng p sut thm thu: =i.C.R.T (do sphn ly cht in ly thnh ion nn lm tngs ht phn t trong dung dch)

Tng im si Dung dch 50% NaOH: si 1200C

Gim im kt tinh: Dung dch 22% NaCl: kt tinh -21 0C

Tnh cht ca DD CL

Tng p sut thm thu: =i.C.R.T (do sphn ly cht in ly thnh ion nn lm tng sht phn t trong dung dch)

mssmdddd cKiTcKiT

TRCiTRniV

,2,2

Tnh cht ca DD CL p sut thm thu: =i.C.R.T

Ap sut cn phitc dng ln dung dch dung minguyn chtkhng th thmthu qua mngbn thm sang dung dch.

5Dung mi

Cc cht c thm in mi cao (VD nc) th c tnh cht ion ho tt phn ly cht in ly tt.

thm in mi tng i D: D = /0

0 = 8,8542.10-12 (J.coulomb/m) (F/m):

thm in mi chn khng

: thm in mi

Lc tnh in gia 2 ion

q1, q2: in tch ca 2 ion tri du

Ch : gia dung mi v cht in lyc th c tng tc (ho hc, vt l).

20

21221

Dr4

q.q

r4

q.qf

(L Coulomb)

Nc S solvat (hydrat) ho

6S solvat (hydrat) ho

Qu trnh tc dng ca ion vi cc phn t dung mi to tp hp tng i bn chc gi l solvate ha. Dung mi nc: hydrat ha.

S ca cc phn t nc rng buc trong hydrat (phc nc) gi l s ca hydrat ha (s phi t).

S solvat (hydrat) ho

Vi dung mi nc: dung dch ca cation kim loi kim, kim th to ra do tng tc tnh in ion lng cc.

Tng tc ny ph thuc: in tch, bn knh, khi lng cation

S solvat (hydrat) ho

lp hydrat ha gn: lin kt cho nhn, do cn obitan trng ca cation v cp in t ghp i ca nc.

lp hydrat ha xa: cc phn t dung mi nh hng khng hon ton, do lin kt lng lo hn.

Cc ligand nc khng c nh trong phc nc m c th thay i v tr. Ligand ny ra i, ligand khc vo th.

S solvat ha, hydrat ha gii phng nng

lng tinh th rn b ph v, lin kt ha hc bph v.

Nguyn nhn ca s in ly

7Source (Volkov, A. G., S. Paula, and D. W. Deamer (1997))

Ion Unhydratedradius (pm)

Hydratedradius (pm)

Na+ 117 358

K+ 149 331

NH4+ 148 331

Ca2+ 100 412

Mg2+ 72 428

Al3+ 53 480

Cl- 164 332

OH- 133 300

NO3- 179 340

Kinetic diameter 270 pm

Phn loi cht in ly

Cht in ly mnh, yu: da vo phn ly .

Cht in ly thc, th: da vo bn chtlin kt trong phn t, tinh th.

Phn loi cht in ly

cht in ly thc (true electrolyte): Lin kt ion

v d: NaCl Tng tc gia ion trong tinh th v phn t dung mi lng cc +

chuyn ng nhit ca ion lin kt mng b t ion lin kt vi dung mi, tch khi mng.

cht in ly th (potential electrolyte): Cc loi linkt khc:

v d: HCl Tng tc lng cc - lng cc + chuyn ng nhit Ph hy

phn t c cc thnh ion hydrat ha ion tng tc nc to ion H3O

+ (oxonium, hydronium).

Phn loi dung mi

- Dung mi proton (Protic solvents): Cho H+, to linkt hydro gia DM v cht tan c th ha tan, phnly, solvat ha cc ion.( H2O, ethanol, buthanol,)

- Dung mi aproton (aprotic solvents): C nhngcp e- dng chung c th solvat cc cation, to ccdung dch ion. (Acetone, Acetonitrile,..)

Non-polar solvents

polar aproticsolvents

Polar proticsolvents

Increase polarity

82. Tnh cht nhit ng

Cht in ly mnh, phn ly hon ton

M+A- +Mz+ + -A

z-

m: nng molan: mol / 1000g dung mim+ = +.m m- = -.m

+, - : h s hot ca cc ion c nng m+, m-

a+, a- : hot ca iona+ = +.m+ a- = -.m-

a1 , a2 : hot ca dung mi (1) , cht tan (2)chn trng thi chun sao cho: (a+)

+.(a-)- = a2 (xem SGK)

Th ho hc ca cc ion

+ = +0 + RT.lna+

= +0 + RT.lnm+ + RT.ln+

- = -0 + RT.lna-

= -0 + RT.lnm- + RT.ln-

Th ho hc trung bnh ca cc ion

/1

00

)a.aln(RT....

Cc i lng trung bnh ca cc ion: = (+

+.--)1/

m = (m++.m-

-)1/ = m(++.-

-)1/

a =(a++.a-

-)1/ = .m

Th ho hc trung bnh ca cc ion tnh cho 1 ion-mol:

a = (a++.a-

-)1/

(Hot trung bnhca cc ion)

l i lng c trng cho sai lch nng dung dch thc so vi dung dch trang thi l tng.

= + + -

91. Hot mol ca mui (a2): xc nh bng thc nghimging hot cu t trong dd cht khng in ly

2. Hot trung bnh ion (a)

a = a2

Hot ca mui ha tan

Quan h:

Cc loi nng trung bnh

m = (m++.m-

-)1/

121 /).1000(/1000 McMc

c

Mm

mx

x = (x++.x-

-)1/

c = (c++.c-

-)1/

Molan

Phn mol

Mol/lit

: khi lng ringdung dch (g/ml)

Quan h:

Cc loi h s hot trung bnh

m = (m++. m-

-)1/

)1000

)(ln(ln)

1000

.1ln(lnln

0

21

0

1

MMcMmcmx

x = (x++. x-

-)1/

c = (c++. c-

-)1/

Molan

Phn mol

Mol/lit

, 0 : khi lng ring dung dch, dung mi (g/ml)

Th ho d

- lt = .RT.lnNguyn nhn: tng tc gia cc ion vi

nhau, gia cc ion vi phn t dungmi v gia cc phn t dung mi vinhau (khi c ion).

*Dung dch rt long tng tc khngng k = 1

ngha ca : xc nh s khc bit gia dung dchthc v dung dch l tng

10

Lc ion (I)(Ionic strength)

Trong vng dung dch long ca chtin ly mnh, ph thuc vo lc ion:

Lc ion I ca mt dung dch:

Im = 1/2.(mi.Zi2)

Nu dung dch ch c 2 loi ion:

Im =1/2(m+.Z+2 + m-.Z-

2)

= 1/2(+.Z+2 + -.Z-

2).m

IC = 1/2.(Ci.Zi2)

mi: nng molanCi: nng thc ca cc ion, khng k nphn khng phn ly.

Lc ion (I)

nh lut thc nghim Lewis Randall

Trong vng nng long ca cc dung dch,h s hot trung bnh ca mt cht in lymnh c gi tr nh nhau i vi tt c ccdung dch c cng lc ion.

Lc ion (I)

Trong mt dung dch cht in ly mnh, khng ph thuc vo bn cht cacht in ly khc thm vo, ch phthuc nng v ho tr ca n.

3. nh lut gii hnDebye-Huckel

11

Debye-Huckel a ra cng thc xc nh hs hot ion i:

Cii IZA ..lg2 (Phng trnh gn ng bc 1)

1000...

.8

2.303,20

2

0

2

0

Tk

Ne

kT

eA

Vi:

Zi : Ha tr (in tch) ca ionIC = 0.5Ci.Zi

2 : Lc ion (ion-gam/l)

k: Hang so BoltzmannN0: So Avogadro: Hang so ien moie0: ien tch ca ien t = 4,8 . 10

-10

nh lut gii hn Debye-Huckel

Cii IZA ..lg2

Vi dung mi l H2O 25oC:

Xc nh h s hot ion: i

Cii IZ ..509,0lg2

Gii hn ca PTG bc 1: dng cho dd long (C 0.01M, I= 0.01-0.03)

ca cht in ly 1-1

Cii IZA ..lg2 (Phng trnh gn ng bc 1)

Xc nh h s hot ion: i

(Extended Debye-Hckel equation)

a (nm): radius of the hydrated ion (Bn knh hydrate ca ion).

Phng trnh gn ng bc 2

(I 0,1)


12

Phng trnh gn ng bc 3

(I 0,5)


C: hng s thc nghim

Xc nh h s hot trung bnh ion:

.lg = +lg+ + -lg-

zz AMAM

CIAZZ

22

lg

Do: + .Z+ = - Z-

mC IAZZIAZZ'lg

)( 0' AA

Vi dung mi l H2O 25oC: A A = 0,509 (mol/l)-0.5

= (++.-

-)1/

= + + -

(xem SGK)


Xc nh h s hot trung bnh ion:

mC IAZZIAZZ'lg

IZZ .509.0lg

C (mol/l)

NaCl ZnSO4

(L

thuyt)

(Thc

nghim)

(L

thuyt)

(Thc

nghim)

0,001 0,954 0,965 0,812 0,700

0,002 0,946 0,952 0,812 0,700

0,01 0,840 0,906 0,517 0,387

13

C

C

C IZZI

IAZZ )(1,0

1lg

PT thc nghim Davies

Xc nh h s hot trung bnh ion, dng nh gi kt qu

(I 0,5)

Xc nh h s hot trung bnh ion: Lu

Vi dung dch thc:

Thay nng bng hot trong cc cng thctnh ton

Hng s cn bng

Gi tr pH

H s hot ion trong dung dch nhiu ion

p dng

Tng nng ion

Tng in tch ion

Nhn xt

14

4. S dn in

Cc loi dy dn

Dy dn loi 1 (kim loi, cht bn dn) : Dn in nh cc e v cc ltrng

Dy dn loi 2 (DDL, cht in ly nngchy,..) : Dn in nh cc ion.

(Dy dn loi 1)

(Dy dn loi 2)

(Dy dn loi 1)q qion (+)cation

ion(-)anion

2Cl- Cl2 + 2e

Fe2+ Fe3+ + e

CATODANOD

Cu2+ + 2e Cu

2H2O + 2e H2 + 2OH-

Phn ng oxi ha Phn ng kh

S in phn

nh lut 1: Lng cht b tch ra hay bha tan khi in phn t l thun vi inlng i qua dung dch in ly

m= k0It = k0.q

k0: ng lng in ha

q: in lng (C- culong= 1 Ampe.giy)

nh lut in phn Faraday

15

nh Lut 2: Cng mt in lng i qua cc cht in ly khc nhau th lngcht b chuyn ha s t l thun ving lng ha hc ca chng

S Faraday: F= 96.500 C : in lng cn thit chuyn ha 1 ng lng gam (lg) ca mt chtbt k.

Hiu sut dng in: = mthc/mlt (

16

(-1.cm-1)

C (M)

nh hng ca nng n :

Cht in ly mnh (vd: HCl): nng thp: chuyn vn ca ion

khng ph thuc nng , nn khi C tng th cng tng.

nng cao: m my ion lm gimtc chuyn vn ca ion, gim

Cht in ly yu (vd: CH3COOH): Mt m my ion nh, it nh hng

n tc ca ion, t nh hng n

nng cao: phn ly gim, dnin gim

dn in

dn in ng lng (-1.lg-1.cm2)

dn in ca mt th tch dung dch cha 1 lgcht in ly nm gia 2 in cc phng song song, cng din tch, cch nhau 1 cm.

C

1000.

Vi C: nng ng lng (lg/l)

dn in

(-1lg-1.cm2)

C (lg/l)

(-1lg-1.cm2)

C1/2 (lg/l)1/2

nh hng ca C n :

- Cht in ly mnh: gim chm khi C tng, quan h =f(C1/2) l ng thng.

nh lut Kolhrausch 1:

= - A.C1/2

Vi:

: dn in ng lng gii hn;

A: h s thc nghim

- Cht in ly yu: gim nhanh khi C tng, quan h =f(C1/2) l ng cong.

dn in

Cc k hiu v gii thch: (upsilon)

+ , - : tc chuyn vn ca cation, anion (cm/s)ph thuc bn cht, nng , T, nht, cng in trng ngoi,

0+ , 0- : tc tuyt i hay linh cation, anion (cm2.s-1.V-1)

+ = 0+.(E/l) ; - = 0-.(E/l) [E/l: cng in trng ngoi]

C, : Nng ng lng (lg/l), phn ly ca cht in ly

C. /1000 (lg/cm3) : S lg cation, anion trong 1cm3

Tc vn chuyn ion & dn in

17

S lg cation, anion chuyn vn qua tit din S (cm2) trong 1s:

C. /1000 (lg/cm3)

S (cm2)

cation

anion

C. /1000 (lg/cm3)


Tng in lng chuyn bi cation, anion qua tit din S (cm2) trong 1s:

l

EFCSFCSIII

1000

....).(

1000

...).( 00

l

CSE

l

SE

R

EI

1000

..... Theo nh lut Ohm:

Do :

= .F.(0+ + 0-)


Vi cht in ly mnh (=1):

= F.(0+ + 0-) = + + -

Vi cht in ly yu ( (baz) >> (mui)


18

Linh ca ion H+ v OH-

oH+ v oOH- rt ln so vi o ca cc ion khc.

Nguyn nhn:

Di in trng ngoi, ion H+ v OH- chuyn vn trongnc theo c ch dy chuyn

H+ + H2O H3O+

H-O-H + O-H H-O + H-O-H

H

+

H

+

H H

H-O + O O + H-O

H

-

H

-

H H


Ion oi .105 (cm2.s-1.V-1)(dd v cng long 25oC)

H+ 363,0

OH- 205,0

Na+ 52,0

Cl- 79,0


Dung mi D Max(HCl)

H2O 81 394

CH3OH 31,2 117

C2H5OH 25,8 27,2

C3H7OH 22,2 9,7

C4H9OH 28,2 4,0

(C2H5)2O 4,4 0,04

dn in VS. dung mi

5. S ti

19

S chuyn vn ca ion (S ti)(Transport number, transference number)

i

ii

q

qt

L t s gia in lng mang bi ion qua tit din ca dd CL v tngin lng i qua tit din .

Nu dd CL ch cha 2 loi ion:

tt 1

Nhn xt: ti ph thuc vo ion cng cp vi ion .

Cht in ly NaCl HCl

t-(Cl-) 0.604 0.170

Phng php Hittorf xc nh s ti

Nguyn tc:

Xc nh ti thng qua s bin thin nng ion vng anolit v vng catolit.

20

Trc khi in phn

Trong khi in phn

Sau khi in phn

Anolit Gia Catolit

V d: in phn dd HCl, in cc tr


Lng cht in ly gim:

- anolit : na- catolit : nc

1)/(

1

1)/(

1

ac nnt

Lu : Do s solvat ha, dung mi cng di chuyn theo ion c skhc bit Ti (thc) v ti (biu kin, theo PP Hittorf). Trong ccdd long, s khc bit ny t.


6. Phng php o dnin & ng dng

Phng php o dn in

- Dng cu Wheatstone:Khi G=0: R1/R2= R3/Rx

- Dng bnh o dn:

21

ng dng

- Xc nh nng lng tiu th trong qu trnh inphn

- Xc nh hm lng mui trong cc dung dch (vd: trong ni supde)

- Xc nh bc ca acid

- Xc nh ha tan ca cc cht kh tan

- Trong phn tch: php nh phn in dn

Php nh phn in dn

Nguyn tc:Do dn in c bit ln caion H+ v OH- so vi cc ion khc m c s thay i dnin ca dd.

HCl bngNaOH

Acid yubngNaOH

Hn hpacid mnh, yu bng

NaOH

KCl bngAgNO3

Php nh phn in dn

PIN V iN CC

Chng 6

(Bi ging tm tt)

22

Ni dung

1. Pin in ha

2. Nhit ng hc pin v in cc

3. Phn loi pin v in cc

4. in th khuch tn v pin c ti

5. o v ng dng php o sc in ng

6. Cc ngun in ha

Pin in ha

Zn + CuSO4 = ZnSO4 + CuH0298= -51820 cal/mol

G0298= -50710 cal/mol

-2e +2e

Ni 2 in cc bng dy dn loi 1 e- s di chuyn t incc Zn qua in cc Cu, to thnh dng in- HA nng INnng.

Pin in ha

Pin in ha (pin, nguynt Galvanic): l mt hbin i ha nng thnhin nng, nh phn ngoxy ha kh trn in cc.

Ha nng

in nng

K hiu pin

(-) Zn ZnSO4 CuSO4 Cu (+)

(-) Zn ZnSO4 CuSO4 Cu (+):.

(-) Pt, H2 H+ Fe3+ Fe2+ , Pt (+)

: in ccdung dch, cc thnh phn in cc

: dung dch- dung dch(khng c th khuch tn)

:. : dung dch- dung dch(c th khuch tn)

, : cc thnh phn cain cc

Pin in ha

23

Lp in tch kp

- Khi +k > +

dd : cation tch khi b mt kim loi i vo dd, li e- b mt tch in (-) ht cc cation cn tr qu trnh ha tan. Khi cn bng : lp in tch kp

+k > +

dd

+k < +

dd

- Khi +k < +

dd : cation kt ta trn mt kim loi b mt tchin (+) ht cc anion cn tr qu trnhkt ta. Khi cn bng : lp in tch kp

Pin in ha

Th in cc ()

- Lp in tch kp gia ranh gii incc- dung dch lm xut hin mt bcnhy th (BNT)

- BNT ph thuc: bn cht KL, dung mi, nng ion, v nhit

Pin in ha

Th in cc ()

- Do khng th xc nh gi tr tuyt i ca BNT nndng 1 in cc chun so snh.

- Ghp in cc chun, lm cc (-), vi in cc khost , lm cc (+) Sc in ng ca pin (E) = : th in cc

- : s khc bit th ca in cc so vi in ccchun

- in cc chun: in cc Hydro : oH+/H2 = 0 (V)

Pin in ha

Bng th in cc chun

Bng th in cc chun ca cc cp Ox/Kh: gi tr o298 iu kin chun (a=1, 25

0C)

Nu Kh c tnh kh > H2 : o

298 < 0 V d: o298 (Zn

2+/Zn)= -0,7628V, nn2H+ + Zn = H2 + Zn

2+

Nu Ox c tnh oxy ha > H+ : o298 > 0 V d: o298 (Cu

2+/Cu)= +0,337V, nnH2 + Cu

2+ = 2H+ + Cu

Pin in ha

24

Sc in ng

E= M2/M1 +M1/L1+L1/L2+L2/M2

M2

M1

L1 L2

M2

E

Sc in ng: E= bc nhy th

: th galvani- hiu th gia 2 im nm su trong lng 2 pha khc nhau-cha c pp xc nh trc tip.

L1/L2 : th khuch tn- nh v c th loi tr

E = M2/M1 +M1/L1+L2/M2

Pin in ha

Xt pin (A) : (-) M2 M1 L1 L2 M2 (+)

EA= M2/M1+M1/L1+L2/M2

V 2 pin: (B): (-) M0 L0 L1 M1 M0 (+)

(C): (-) M0 L0 L2 M2 M0 (+)

EC-EB= EA

Nu M0 L0 l in cc chun (H2H+): EB= (-) v EC= (+)

Do : EA= (+) - (-) (Khi khng c th khuch tn)

EB= M0/L0+L1/M1+M1/M0

EC= M0/L0+L2/M2+M2/M0

Sc in ng

Pin in ha

EA= (+) - (-)

Sc in ng ca mt mch in habng hiu th gia in cc dng vin cc m (khi khng c th khuch tn)

Sc in ng

Pin in ha Nhit ng hc ca pin & in cc

Cng in ca pin

Khi pin lm vic thun nghch nhit ng thcng in ca pin l cng hu ch cc iAmax. Cng in khi chuyn ha 1 mol cht:

Amax= q.E = nF.E

Khi T,P= const, theo nguyn l 2 nhit ng hc: G = -Amax

G= -nFE

(n: s e trao i)

25

Phng trnh NERNST (nh hng ca nng n E v )

Phn ng xy ra trong pin: aA + bB dD + eE

PT ng nhit Vant Hoff: G = -RT ln(Ka / a )

nFE= RT ln(Ka / a )= RT lnKa - RTlna

bB

aA

eE

dD

aaa

aa

Fn

TRK

Fn

TRE

.

.ln.

.

.ln

.

.

bB

aA

eE

dD0

a.a

a.aln

F.n

T.REEHay: (Phng Trnh NERNST)

Nhit ng hc ca pin & in cc

(E0: S khi ai=1)

Phn ng xy ra in cc: Ox + ne Kh

PT NERNST tr thnh:

Ox

Kh

a

a

Fn

TRln

.

.0

25oC :

0: th in cc khi hot ca cc cu t bng 1


Phng trnh NERNST (nh hng ca nng n E v )

nh hng ca nhit

PT Gibbs - Helmholtz :

G = H - TS

PT

)G(.THG

PT

FEnTHFEn

)..(...

PP T

E.T

F.n

H

T

)nFE(

F.n

T

F.n

HE

dT

dET

F.n

HE


nh hng ca nhit

dT

dET

F.n

HE

dT

dE : h s nhit ca S

nF

S

T

G

nFdT

dE

P

)(1 H s nhit ca S t l vibin thin entropy


26

nF

S

dT

d

Va: )298T.(

dT

d0TT

Tng t, i vi th in cc:

nh hng ca nhit


V d: Xc nh H, S, G ca phnng:

Ag + 0,5 Cl2 = AgClBit pin: (-) Ag, AgCl HCl Cl2, Pt (+) c:E = 1,132 V ; dE/dT = -0,000477 V/K



Xt chiu phn ng = E ??

H thc Luther (c SGK)

(h-n).h/n = hh - nn


27

Phn loi in cc- mch in ha

Cc loi in cc

in cc loi 1: in cc thun nghch cation/anion gmkim loi (hoc phi kim) nhng vo dd chaion ca n

Mn+M: Mn+ + ne = MAAn-: A + ne = An-

Cu2+Cu: Cu2+ + 2e = CuSeSe2-: Se + ne = Se2-

V d:


Cc loi in ccin cc loi 1:

nn

M0

M

M0 alnF.n

T.R

a

aln

F.n

T.R

nn A

0

A

A0

a

1ln

F.n

T.R

a

aln

F.n

T.R

PT NERNST:

Mn+M: Mn+ + ne = MAAn-: A + ne = An-

in cc loi 2: Kim loi c ph cht kh tan ca chnhn, nhung vo dd cha anion ca hp chtkh tan

An- MA M: MA + ne = M+ An-

Cl-AgCl Ag: AgCl + 1e =Ag + Cl-

V d:


Cc loi in ccin cc loi 2:

PT NERNST:

nA

0

a

1ln

F.n

T.R

L cc in cc so snh in hnh. V d:

- in cc Calomel: Cl-Hg2Cl2Hg,Pt

- in cc Bc-clorua bc: Cl-AgClAg

An- MA M: MA + ne = M+ An-


Cc loi in cc

28

in cc loi 3: Kim loi tip xc vi 2 mui kh tan cchung anion, nhng vo dd cha cation camui kh tan th hai

Mn+MA, MAM (TMA < TMA)

V d:

Ca2+CaCO3, PbCO3Pb


Cc loi in cc

22 ln..

.0/ PbPbPb

aFn

TR

Phn ng: PbCO3 + Ca2+ + 2e = Pb + CaCO3

23

23

23

23

.;.COCaCaCOCOPbPbCO

aaTaaT

23

32 Ca

CaCO

PbCO

Pba

T

Ta

2ln..

.0'Ca

aFn

TR

in cc loi 3:

Mn+MA, MAM (TMA < TMA)

Ca2+CaCO3, PbCO3Pb


Cc loi in cc

in cc oxy ha-kh: (in cc Redox) Kim loi tr nhng vo dd cha c 2 dng: oxy ha v kh

OxKh, Pt : Ox + ne = Kh

V d:

MnO4-,H+Mn2+, Pt : MnO4

- + 8H+ + 5e = Mn2+ + 4H2O

Fe3+Fe2+, Pt : Fe3+ + e = Fe2+

C6H4O2,H+C6H4(OH)2,Pt :

(/C quinhidron)

o

o

+ 2H+

+ 2e- =

OH

OHQuinon (Q) Hydroquinon (QH2)


Cc loi in cc

n gin:

Phc tp:

in cc oxy ha-kh: (in cc Redox)

PT NERNST:

ox

kh0doxRedoxRe

a

aln.

F.n

T.R

OxKh, Pt : Ox + ne = Kh

C6H4O2,H+C6H4(OH)2,Pt :

(/C quinhidron)

Quinon (Q) Hydroquinon (QH2)

o

o

+ 2H+

+ 2e- =

OH

OH

25oC: Quinh = 0,69976 - 0,059 pH

(Dng lm in cc ch th o pH)


Cc loi in cc

29

in cc kh: Kim loi tr tip xc vi kh v ion ca kh

V d: H+ H2 Pt: in cc hydro

2H+ + 2e = H2

2

2

0

//ln.

.2

.22

HHHHH p

a

F

TRH

25oC:

Khi: pH2= 1atm


Cc loi in cc

H+/H2 = - 0,059 pH

H+/H2 = - 0,059 pH 0,0245 lg pH2

in cc hn hng:

Hn hng ca mt kim loi tip xc vi ddcha ion ca kim loi -

v d: Cd2+ Cd(Hg)

/C hn hng Cadimi (Cd 12,5%) dng ch to pin Weston, c E khng i theo thi gian, dngtrong php o sc in ng.

Mn+ M(Hg): Mn+ + ne = M(Hg)


Cc loi in cc

Mch ha hc- mch nng :

Mch ha hc: pin to thnh do 2 in cc khcnhau v bn cht ha hc.

Pin Jacobi Daniell:

(-) Zn ZnSO4 CuSO4 Cu (+)

Mch nng : pin to thnh do 2 in cc gingnhau v bn cht ha hc nhng khc v hot cadd in cc.(-) Ag AgNO3 (a) AgNO3(a) Ag (+)


Cc loi mch in haMch c ti- mch khng ti:

Mch c ti: khi 2 in cc c 2 dd (gingnhau hoc khc nhau v bn cht) tip xc nhauqua mng xp C th khuch tn.

(-) Ag AgNO3 (a) AgNO3(a) Ag (+)

Mch khng ti: khi 2 in cc c chung mtdd hoc c 2 dd khc nhau nhng khng tip xcnhau trc tip: v d s dng cu mui, mch kp loi b th khuch tn.


Cc loi mch in ha

30

Mch thun nghch v khng thun nghch:

S thun nghch nhit ng ca mt mch inha gm:

- S TN v iu kin lm vic: Khi hot ngE ln hn V mt lng v cng nh: tc lm vic v cng chm.

- S TN ca chnh bn thn mch: xy ratheo chiu no ty hiu in th tc ng


Cc loi mch in haMch thun nghch v khng thun nghch:

Xt pin Jacobi- Daniel:

- Nu V > E : mch in phn

Zn2+ + Cu Zn + Cu2+

- Nu V < E : pin in

Zn + Cu2+ Zn2+ + Cu

h ny l mch TN.


Cc loi mch in ha

Mch thun nghch v khng thun nghch:

Xt pin : (-) Zn CuSO4 Cu (+)

- Nu V > E : mch in phn

Zn2+ + Cu Zn + Cu2+

- Nu V < E : Trong dd khng c Zn2+, nn Cu kt ta ti (-); Cu ha tan ti (+)

Cu + Cu2+ Cu2+ + Cu

H ny l mch khng TN.


Cc loi mch in ha

in th khuch tn

kt: Tn ti trong mch c ti, ti ranhgii tip xc gia hai dd in cc

Nguyn nhn: do linh khc nhau cacation, anion xut hin lp in tchkp xut hin bc nhy th inth khuch tn

31

in th khuch tn

V d:

(-) Ag AgNO3 (a) : AgNO3(a) Ag (+) (Vi a< a).

- AgNO3 khuch tn t (+) sang (-)

- Linh NO3- > linh Ag+

NO3- i qua mng xp nhanh hn

bn tri mng xp tch in (-), bn phi tch in (+) kt

- Gi tr ca kt khong vi chcmV

(-)Ag (+)Ag

-----

+++++

AgNO3(a1) AgNO3(a2)

t+t-

F

kt

kttai EE

Neu t- > t+ tc - > + th kt > 0 Va Etai > E

Neu t- < t+ tc - < + th kt < 0 Va Etai < E

Neu t- = t+ tc - = + th kt = 0 Va Etai = E

'

''

ln

a

a

F

RTkt

in th khuch tn

Bin php loi tr kt- Dng cu mui:

dd m c ca mt mui c linh cation v anion gn bng nhautrong dd keo agar. VD: KCl, KNO3, NH4Cl, NH4NO3, .. kt khng ngk.

- To mch kp: Loi b hon ton kt

(-) Ag,AgCl HCl(a) : HCl(a) AgCl,Ag (+).

(-) Ag,AgCl HCl(a)H2, Pt, H2 HCl(a) AgCl,Ag (+)

in th khuch tn ng dng ca php o S

Phng php o Sc in ng

wx EAC

ACE .

'

Ew: pin mu c S bit, n nh, bn vithi gian pin Weston

Phng php xung i

32

ng dng ca php o S

Phng php o Sc in ng

pin Weston: (-) /C hn hng Cadimi(+) /C thy ngn loi 2

(-) Cd(Hg) (12,5%)CdSO4 ,CdSO4 .8/3H2O (r)Hg2SO4 Hg,Pt (+)

H s nhit ca pin: 5.10-5 V/oC

ng dng o pH

Nguyn tc: o S ca pin gm:

- in cc c bit: in cc Calomel, in cc bc

- in cc c ph thuc pH ca dd incc ch th: in cc Hydro, in ccquinhydron, in cc thy tinh

Chun in th

(-)Hg, Hg2Cl2 | KCl || H+ (x)| ien cc thuy tinh (+)

cal0ttcaltt pH059,0E

059,0

EpH cal

0tt

u iem: khong dung phu gia kem theo.Nhc iem: de v v mang thuy tinh mong 0,01 0,03mm.

Chun in th

ng dng Xc nh h s hot trung bnh ()

V d: Xc inh ca dd HCl nng m.

Lp pin: (-) Pt, H2 (1 atm) | HCl (m) | Hg2Cl2, Hg (+)

Phn ng: Hg2Cl2 + H2 = 2Hg + 2HCl

Sc in ng: HCl0

H

2HCl0 aln

F

T.RE

P

aln.

F2

T.REE

2

)..ln(.

2ln. 020 m

F

TREa

F

TRE HCl

)ln(..

2).ln(.

20 F

TRm

F

TREE

Chun in th

33

- Nu bit Eo : o E, xc inh

- Nu cha bit Eo :

)ln(..

2).ln(.

2 0 F

TREm

F

TRE =Y

Khi m 0 : 1 nn Y Eo

V th Y-m , ngoai suy ti m= 0 thu c Eo

)ln(..

2).ln(.

20 F

TRm

F

TREE

Chun in th

ng dng Xc nh tch s tan (T)

V d: xc inh T ca AgCl

Lp pin: (-) Ag, AgCl | HCl | Cl2, Pt (+)

Phn ng: AgClAgCl2

12

Cl,Ag/AgClCl/Cl2E ClClAgAgClClClCl aa lg059,0lg059,0 0 ,/0 /2 Ta li c:

AgCl0

Ag/Ag

0

Cl,Ag/AgClTlg059,0

AgCl0 Ag/Ag0 Cl/Cl Tlg059,0E 2 V799,0;V358,1 0

Ag/Ag

0

Cl/Cl2

; Eo = 1,136V TAgCl = 1,77x10-10

Chun in th

Ngun in ha hc

- Ngun in s cp- pin: ch dngmt ln.V d: pin kh La Clanch (Zn-C)

- Ngun in th cp- acquy: C thnp in v s dng nhiu ln

V d: Acquy acid, acquy kim

- Pin nhin liu: lm vic lin tc, trctip bin ha nng thnh in nng

V d: pin Hydro-oxy

Pin nhin liu

Pin La-Clanch

Ngun in ha hc

- Ngun in s cp- pin: ch dngmt ln.V d: pin kh La Clanch (Zn-C)

Pin La-Clanch

(-) Zn NH4Cl (20%), ZnCl2 MnO2, C (+)

(-) Zn 2e = Zn+2

(+) 2MnO2 + H2O + 2e = Mn2O3 + 2OH-

Eo = 1,6 V

34

Ngun in ha hc

(-) Pb, PbSO4 H2SO4 (25-30%) PbO2, Pb (+)

(-) Pb + SO42- 2e PbSO4

(+) PbO2 + 4H+ + SO4

2- + 2e PbSO4 + 2H2O

Eo = 2,037 V

Ngun in ha hc

Hydrogen Fuel Cells

(-) Ni, H2 KOH (30-40%) O2, Ni (+)

(-) 2H2 + 4OH- 4e 4H2O

(+) O2 + 2H2O + 4e 4OH-

Eo = 1,23 V

NG HC iN HA

Chng 7

(Bi ging tm tt) Ni dung

1. Hin tng in phn

2. Qu in th

3. ng dng s in phn

4. Php cc ph

5. S n mn in ha

35

Hin tng in phn

Quy c v tn in cc(theo SGK)

Cc m (-): (qua trnh oxy hoa)V d: Zn 2e = Zn2+

Cc dng (+): (qua trnh kh)V d: Cu2+ + 2e = Cu

PIN iN

(-) (+)

Hin tng in phn


anod: (qua trnh oxy hoa)V d: Cu 2e = Cu2+

catod: (qua trnh kh)V d: Zn2+ + 2e = Zn

4H+ + 4e = 2H2

LEO red cat

iN PHN

Catod Anod

Hin tng in phn


LEO red cat

Loss Electron is Oxidation

Reduction at Cathode

Hin tng in phn

Qu trnh in phn H2SO4 vi in cc Pt

(-)Pt (+)Pt

H2SO4

mA

V

CB A

K

Catod Anod

2H2O + 2e = H2(g) + 2OH

0 = -0,83 V

2H+ + 2e = H2(g)0 = 0 V

2H2O - 4e = O2(g) + 4H

+

0 = 1,23 V

2SO42- - 2e = S2O8

2-

0 = 2,01 V

Anod

Catod

Cht Kh mnh

Cht Oxh

mnh

36

Hin tng in phn

Qu trnh in phn H2SO4 vi in cc Pt

anod : 2H2O - 4e = 4H

+ +O2(qua trnh oxy hoa- oxidation)

Catod :4H+ + 4e = 2H2

(qua trnh kh - reduction)

(-)Pt (+)Pt

H2SO4

mA

V

CB A

K

Tng cng: 2H2O = O2 + 2H2

in phn ncCatod Anod

I(mA)

E (V)EfO

A

B

(in phn dd H2SO4)

Xt phn ng:2H2O = O2 + 2H2 G0298 = +56,7 Kcal

Dng in thc hinc phn ng m t nhin n khng thdin ra.

Trong qu trnh in phn H2SO4: Kh O2 v H2 ch thot ra t mthiu in th xc nh - in thphn hy Ef.

Hin tng in phn

in th phn hy (Ef)

+ L hiu in th nh nht cn thit to ragia 2 in cc s in phn bt u(to ra cc sn phm trn cc in cc)

+ Khi khng c Qu Th, Ef bng S capin to thnh t cc in cc.

Hin tng in phnV du:ien phan dung dch HCl 1N, ien cc Ptth Ef =1,31 V

Xet Pin: (-) Pt, H2HCl HCl O2 , Pt (+)Ta co:

0 H2/H+=0 V ; 0

Cl-/Cl2 =1,36V

Eo=1,36 V (Ef Eo)

Hin tng in phn

37

I(mA)

E (V)EfO

A

BKhi in phn H2SO4, s to khO2, H2 trn 2 in cc, to thnhpin, chng li in th ngoi:

(-) Pt, H2 H2O (H2SO4)O2, Pt (+)

Hin tng in phn

S phn cc ha hc (in ha)

(-)Pt (+)Pt

H2SO4

mA

V

CB A

K

- +

H2OH2O2

E

(+)Pt, O2 H2O

(-) Pt, H2 H

+

R

EEI

p

Ep: in thphn cc

Hin tng in phn


0 O2,H+/H2O=1,23V 0 H+/H2=0V Ep =+ - -

(-) Pt, H2 H2O (H2SO4)O2, Pt (+)

2

4

0/4

2

0/)(

2

2

22

2

2

22

.ln.

.

.

.ln.

.

.

OH

OHOOH

OH

OH

OOHa

Pa

Fn

TR

Pa

a

Fn

TR

(-): 2H+ + 2e = H2

2

2

2

2

2

0

/2

0

/)(ln.

.

.ln.

.

.

H

H

HH

H

H

HH P

a

Fn

TR

a

P

Fn

TR

(+): 0,5O2 + 2H+ + 2e = H2O

Hin tng in phn


(-) Pt, H2 H2O (H2SO4)O2, Pt (+)

-

+

Ep = + - -

Hin tng in phn


38

Ep = (+) - (-)

- Khi E bn ngoi tng: O2, H2 to thnh tng (+) tng v (-) gim Ep tng

- Khi PO2, PH2 bng p sut kh quyn Epmax. Lc E bn ngoi l Ef

Xut hin bt kh H2 , O2

Hin tng in phn

S phn cc ha hc (in ha) S phn cc nng

S chenh lech the ien cc do skhac nhau ve nong o tao ra.

Hin tng in phn

S phn cc nng

Xt in cc: Mn+/M

Ban u (gi s =1): Cln.nF

RT0

Khi co phan ng ien hoa: Mn+ +ne = M

S0/ Cln.

nF

RT

CS : nng st b mt in cc (Cs C)

Hin tng in phn

S phn cc nng

Xt in cc: Mn+/M

Cln.nF

RT0

0ln./ C

C

nF

RT SC

S0/ Cln.

nF

RT

-Khi in cc l catod: Mn+ + ne = M Cs < C

0ln./ C

C

nF

RT Sa

-Khi in cc l anod: M - ne = Mn+

Cs > C

Hin tng in phn

39

Qu th

Qu th ( /eta/): S khc bit gia inth phn hy v tng cc inth cn bng trn cc in cc

= Ef - E/c

Qu th

Nguyn nhn: do tc tng i nh ca qu trnh inha, mi phn ng in ha l mt qu trnhphc tp, nhiu giai on.

V d: in phn dd CuSO4, in cc Pt

Ef = 1,3 V ; Edc = 0,89 V = 0.41 V

Phng trnh Tafel

= a + b.lgi

Trong o: : qua the hydro (V).i: mat o dong ien A/cm2.a: phu thuoc vt liu in ccb: phu thuoc qua trnh. b

nF

RTln.303,22

Khi n=1, T=25oC : b 0.166 Khi i tng 10 ln, tng 0.166V

Qu th

Gi tr cc hng s a, b ca PT Tafel cho phn ng catodthot H2 trn cc kim loi 25

oC

Kim loai Dung dch, nong o a b

Pb H2SO4 1,0N 1,533 0,118

Hg H2SO4 5,0N 1,400 0,116

HCl 1,0N 1,390 0,119

KOH 0,1N 1,430 0,093

Zn H2SO4 1,0N 1,240 0,118

Pd KOH 0,1N 0,637 0,125

Pt trn HCl 1,0N 0,100 0,130

Pt HCl 0,5N 0,073 0,028

Phng trnh Tafel

Qu th

40

Cc thuyt qu th Hydro

S phong ien cua ion H3O+ to kh H2 rat

phc tap, gom nhieu giai oan noi tiep:

- Khuech tan: H3O+ khuech tan t dd be mat ien cc

OHHOH 23

- Phong ien va hap phu H:

- Ket hp: ddHH2 2hf

- Thoat kh: khHddH 22

- Kh nc:

He1H hfH|MeMeH v

Qu th

Thuyt kt hp: (Tafel, 1905)- Giai on chm: Giai on kt hp (mol ha)

Khi ien phan, nong o nguyn t H tren be mattang chuyen the ien cc ve pha am hn.

Qu th

Cc thuyt qu th Hydro

Ox

Kh

a

a

Fn

TRln

.

.0

Thuyt kt hp: (Tafel, 1905)

= a + 0,029lgi

Gia tr b = 0,029, bang so vi gi tr thcnghim.Nguyn nhn:do khng tnh n cu trc b mt in cc, stng tc gia cc nguyn t H.

Cc thuyt qu th HydroQu th

Thuyt phng in chm:

Giai on chm: s phong ien cua cac ion (do can nang lng hoat hoa)

Tc :

ilg.058,0

ailn.F.

T.Ra

Neu = 0,5 th b = 0,058/0,5 = 0,116Phu hp vi phng trnh thc nghiem cua Tafelkhi chn = 0,5 .

(xem SGK)

Cc thuyt qu th HydroQu th

W = k0. e-E/RT.[H3O

+]

41

ngha ca qu th

im bt li:ien phan nc: neu khong co qua the th E = 1,23V.Nhng thc dung: E = 1,7V, tang hn khoang 40%.

im c li:- Ma kim loai: qua the hydro tren kim loai thng rat lnnen co the ma kim loai t dung dch ma khong co hydrobay ra.

- ien phan dung dch NaCl vi catot Hg

- Nap acquy ch.

Qu th

ngha ca qu th

0 (Cu2+/Cu) = 0,337 V 0 (H+/H2) = 0V

Qu th

Electroplating

ngha ca qu th

0 (Pb2+/Pb) = -0,126 V 0 (H+/H2) = 0V

Qu th

Np in acquy ???

PbSO4 + 2e = Pb + SO42-

2H+ + 2e = H2

in luyn kim v m in

ng dng ca in phn

- Sn xut nhm: in phn hn hp Al2O3 Cryolit (3NaF.AlF3)

- Tch v tinh luyn Kim Loi: ng dng trongsn xut kim loi t qung: Cu, Zn, Ca, Co, Fe, Mn, Cr,

- S dng phc cht trong m kim loi: v ddng [Ag(CN)2]

- ; [Cu (NH3)4]2+

42

ng dng ca in phn

Phn ng in ha oxy ha kh

- C th dng trong tng hp cc chthu c. Tuy nhin, c ch ca ccqu trnh ny l phc tp

Php cc ph

Phng php Volt-Ampere

Phng phap nghien cu qua trnh ienhoa da tren c s tm moi quan hecng o dong ien la ham cua hieuien the: I = f(V).

Mt dng ca phng php Volt-Ampere: Php cc ph (polarography)

1 : Mao qun2,5 : Cc in cc3 : Ngun in4 : Potentionmeter (in th k)6 : Bnh o

S cc ph ca Heyrosky

Php cc ph

ng dng: C th dng phn tch nh tnh (da vo i) , nh lng (da vo Ii) h nhiu cu t

I (mA)

U (V)i

Ii

Php cc ph

43

S n mn in ha

n mn kim loi l hin tng kimloi b mi trng oxy ha. Theo cch, c 2 loi n mn:

n mnha hc

n mnin ha

S n mn in ha

n mn ha hc: Qu trnh n mntun theo qui lut ng hc ca phnng d th, khng km theo s xuthin ca dng in

V d:

n mn do cc kh kh: O2, H2S, SO2,.. ; hoc cc cht lng khng in ly: xng, nha,..; cc kh nhit cao.

S n mn in ha

n mn in ha: Qu trnh n mntun theo qui lut ng hc in hav km theo s hnh thnh cc pin tvi.

V d:

n mn khi c mt cht in ly nh trongkhng kh m, di t,..

S n mn in ha

n mn in ha

$200 billion dollars (or 4% of the gross domestic product) is spent in the United States each year to prevent or repair the damage done by corrosion.

Economically, one of the most important metals to corrode is iron and one of its alloys, steel.

Almost 20% of the iron and steel produced in the United States each year is used to replace objects that have corroded.

(Ngun:http://science.jrank.org)

44

C ch ca qu trnh n mn in ha

cc (+) ca pin- qu trnh kh:

0.5 O2 + H2O + 2e 2OH-

Nu mi trng acid: 0.5 O2 +2H+ + 2e H2O

cc (-) ca pin- qu trnh oxy ha:

Me 2e Me2+

S n mn in ha

C ch ca qu trnh n mn in haV d: S n mn ca thp

Hnh thnh cc pin t vi trong mi trng m: (-) Fe Fe2+ H2O O2, Fe (+)

S n mn in ha

S n mn in ha

n mn in ha

(-) Fe Fe2+ H2O O2, Fe (+)

(-) Fe 2e = Fe2+

(+) 0,5O2 + 2H+ + 2e = H2O

0,5O2 + H2O + 2e = 2OH-

0 (Fe2+/Fe) = - 0,44 V

0 (H2O/H+,O2) = 1,23 V

0 (OH-/O2) = 0,40 V

Cc phng php bo v kim loi

Dng lpph bo v

X l mitrng

Dng dngin ngoi

S n mn in ha

45


Dng lp ph bo v:

- Ph bng cht hu c: sn

- Ph kim loi hoc hp kim bn vng: sttrng km (tn), st m kn, m crom,

- Ph bng mng oxyt bn, cch ly kim loivi mi trng: v d dng mng Al2O3

S n mn in ha


S n mn in ha

0 (Zn2+/Zn)= -0,76 V

0 (Fe2+/Fe)= -0,44 V

(-) ZnZn2+ H2O O2,Fe (+)


X l mi trng: - Gim cht kh cc, O2: un nng, thi kh,..- Thm vo cc cht c ch lm gim qu trnh

n mn

Dng dng in ngoi: - Phng php bo v catod- Phng php bo v anod

S n mn in ha

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