Nguyên tố Ganvani và cân bằng điện cực

8/13/2019 Nguyn t Ganvani v cn bng in cc

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TH IN CC

V PIN IN HA

Chng5


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1. Khi nim Thinha

2. Hiuthtrn ranh giipha

3. Thincc4. Nhitnghcpin inha

CHNG 5


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animal electricityLuigi Galvani (1737-1798)


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1. Khi nimthinha

Ha th(chemical potential): phn ng gp ca mi cht vonng lng chung ca h ha hc (xc nh bng cng a cut I khng mang in t trng thi kh i vo pha )

mTh in ha: Khi cht l ht tch in (ion hoc in t) th cn

phi tnh thm c tng tc ca ht tch in vi in trng.Phn ng gp ca ht tch in vo nng lng chung ca h

th in ha (electrochemical potential).mi


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Ha th (hay th in ha nu l ht tch in) l i lng cho bitcc tnh cht nhit ng s bin i nh th no khi thay ilng cht trong h Cng a 1 mol ht t chn khng voh.

Th in ha v Ha th

Mt cch hnh thc c th vit:

iji

i

NTPN

G

,,

m

F

iji

i

NTPN

G

,,

m


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Th in ha l cng chuyn mt mol ht tch in t chn

khng vo bn trong mt pha no .

i iZ F m m

- Nith(Inner electrical potential): bininnglngdochuynhtiqua lpinkp trn bmtpha + nnglngtngtccaivicc intch tdo trong pha .

Th in ha, ni th, ngoi th,

(E.A.Guggenheim 1929)


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mm FZiii

FZi

mi

mm FZiii

Gi thit: pha hnh cu, tch in;in tch phn bu thnh lp mng trn b mt cu

i(Zieo) trong chn khng.

i

i

i Hp phn ha hc i: cng chuyn it xa v

cng ti mt im bn trong ca qu cu (pha ) tc b in tch b mt

Hp phn inZiF: cng cn chuyn 1 molcu t i nmt im bn trong qu cu rngc b mt tch in

Th in ha : cng phi tiu tn chuyn

cu t inmt im bn trong pha tch in .

mi


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Ht khng tch in (Zi= 0):

mm ii

Ht bt k :

i

o

ii aRTln, mm , lnoi i i iRT a z F

m m

Pha nguyn cht

(Zi= 0; a

i= 1):

mm,o

ii

i i iz F m m

Th in ha v Ha th

in t trong kim loi klkle

kl

e Fmm )1(


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2. Hiuthtrn ranh giipha


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iu kin cn bng gia hai pha v:

mm ii

Th in ha v Cn bng pha

1) CB trn ranh gii 2 KL tip xc

21 21

21

mmmm

FF MeM

e

M

e

M

e

Th Galvani :

F

M

e

M

eMMM

M

12

122

1

mm

Trong cht rn nh kim loi, bn dn th in ha tng ng nnglng mc Fermi meM=NaEF)


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1212

Cc mc nng lng

Nguyn t

NL

E = 0

Mt phn tnh

Mt phn tln

Mc lpy

Mctrng

HOMO

LUMO

McFermi

Mc chn

khng

Tnh cht ha hc c quyt nh bi trao i in tchuyn di t mc y trng.

Vt liu khi

Mc Fermi trong KL ging nh mc HOMO trong 1 phn t


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Cu trc di nng lng

Kim loi

Cc dict li

Di ha tr

Khong cchv cng nhgia trngthi y vtrng

Khong cchnh (nhngkhc 0) giatrng thi yv trng

Khong

cch lngia trngthi y vtrng

Band Gap

Chng ta tp trung vo kim loi.

Bn dn Cht cch in


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McFermi Tp trung vo in t gn ranh gii y/trng.

E=0 (mc chn khng)

EF(mc Fermi)

Nnglng tithiu tch rakhi mu

Phn b cc trng thi nng lng ca mi vt liu l duy nht.

KL 1 KL 2

EF(mc Fermi)

in t cng gn mc chn khng th cng lin kt yu vi khi rn hay, nng lng ca in t cng cao

Mi vt liu c mt mc nng lng Fermi khc nhau. Trong p.t, cc mc LUMO va HOMO xc nh, nhng trong KLc

rt nhiu trng thi xung quanh mc Fermi


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Hai vt dn tip xc nhau

dng in t+++

++

Dn ti cch bit in tch

Hiu th tip xc

Mc Fermi nh nhau trong ton h


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Ion trong dung dch cu trc in t ca ion: HOMO, LUMO, HOMO-LUMO gap.

Lowest Unoccupied Molecular Orbital

Highest Occupied Molecular Orbital

HOMO-LUMO Gap Mc Fermi

- Trng thi ni phn t (quay, dao ng, ) v tng tc ca ionvi dung mi.

- Mc Fermi!


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Kim loi trong dung dch in ly

Cc mc Fermi c

xp thng hng

in tch chuyn di cn bng cc mc

Fermi,Gy ra cch bit intch v hiu th tipxc.

+

+

+


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Hai dung dch in ly

+

+

+

Mc Fermi

Xut hin cch bit

in tch lmbng mc Fermiv gy ra hiu thtrn ranh gii


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Th tip xc

Trong mi mch u c th tip xc khi c haivt liu khc nhau tip xc vi nhau.

Trong chng trnh mn hc chng ta quantm nht n giao din kim loi dung dch.


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(Hiu)ThVolta: chnh lchinthgiahai imtrong chn khng; mtimgnbmtcapha thnht, cn imkia th gnbmtcapha thhai. ThVolta l hiungoithcahai pha.ThVolta c thoc.

(Hiu) thGalvani: hiuthgiahai imnmtrong lng hai pha(gisl 2 pha v ) hay chnh l hiunithca2 pha v .Hai pha ny c thl hai kim loikhc nhau hay mtkim loiv mtchtlng, hay giahai pha lng, .

Th Gavani khng th o c

ThGalvani v thVolta


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Thbmt, thGalvani v thVolta

Chn khng

pha pha

Hiu th volta

Hiu th galvani


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Sc in ng (the electromotive force)

ij= ij

ijbc nhy th trn ranh gii gia vt dn ivj; ith ca vt dn i.

Sc in ng(s..) E ca mch (123NM) :

E = 12+ 23+ ... + NM

E = M1S.. ca mch ch gm cc kim loi s bng hiu in th gia vt dn cui

cng v vt dn u tin.

Mch h ng: vt dn u tin v cui cng hon ton ging nhau.

Nu mch h ngch gm ton kim loi E = 0

S.. ca mch h ng c t nht 1 cu thnh l cht in ly s khc 0.pin in hahay nguyn t galvani


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Pin in ha nguyn t Galvani

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Fig 18-14 Pg 877

The copper/zinc electrochemical cell. The voltmeter measures thedifference in electrical potentials between the two electrodes.

Hm Gibbs v Cng


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Hm Gibbs v Cng

dGT= dHT- TdS

dHP dUP PdVdGT,P= dUT,P+ PdV - TdS

dGT,P= TdS PdV + Win+ PdV - TdS

dU = q + W

q = TdS

W = PdV + Win

dUT,P= TdS PdV + Win

dGT,P= Win

Nh vy, hm Gibss l tm im ca in ha hc, v n xc nhlng cng in ti a c th nhn c t mt h ha hc.

Hm Gibbs v Sc in ng (Hiu th pin)


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Hm Gibbs v Sc in ng (Hiu th pin)

dGT,P

= Win

dGT,P= Win

ngoi

Win ngoi= V.Q

V: hiu th gia 2 u mch

Q: in lng di chuyn

H in haV = Epin(sc in ng)

(nu h thun nghch)Q = n.F

(khi 1 mol cht phn ng)

/l Faraday

dGT,P= Winngoi, max= nFEp in

Wn GT,PThc t:

Mi li h i i h hi


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Mi lin h gia sc in ng v cc hm s nhit ng

nF

GE

P

T

GTHG

dT

dET

nF

HE

H s nhit ca s...:21

21

TT TT

EEE

d

dE

(E1v E2s.. ca

nguyn t ti nhit

T1v T2)

TT d

dEnF

GS

Td

dEnFTnFEH

G =nFE Cn bng, ng

nhit, ng p

S v hng s cn bng ca phn ng


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g g g

aA + bB cC + dD

mba

BA

DCoii

aaaaRTG

dC

.

.ln

GT,P= i.mi

i

o

ii aRTlnmm

1

ba

BA

DC

i

a.a

a.aa

dC

Go= imoi

bB

aA

dDcC

aa

aaRTGG.

.ln0

baBA

DC

o

PT

aa

aanF

RTnFGE

dC

.

.ln,

(sp)

)(ln

.

.ln

o

o

jj

ii

d

D

c

C

bB

aA

a

tca

nF

RTEE

aa

aa

nF

RTEE

phng trnh Nernst


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trng thi cn bng G = 0 nn

00

KlnRTG

cba.a

a.alnRTGG

P,T

BA

DCo

P,TP,T ba

dC

Go=nFEo=RT ln K

cbba

BA

DC

aa

aaK

dC

.

.

cbKnF

RTE lno


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Trng thi tiu chun (i chng)

Trng thi tiu chun thng c chn l:

p sut = 1 bar(105Pa)

Nng = 1 molal(mol cht tan/kg dung mi)

Nhit = 298 K (25C = 298,15 K)

NHNG

Tt c cc hm nhit ng u ph thuc vo trng thi; khng cgi tr tuyt i (tr ENTROPY: c tr tuyt i theo l thuyt).

nh lng cc hm nhit ng, quy c chn trng thi tiuchun.

T thi ti h (i h )


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n v ca p sut thng dng l atmosphere.

1 atm = 1,0134 bar

Trng thi tiu chun i vi p sut thng l 1 atm

Trng thi tiu chun v nng hay dng nht : 1 M (mol/lit).

Trng thi tiu chun (i chng)


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Dng chuynintchin tch chuyn ng trong pin nh th no?

NO3

Zn

NO3

CuZn2+

Cu2+Cl K+

e e

Nu nng 1 M:pin k tiuchun v hiu tho c = + 1,10

V.

V +


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Bnh in phn

NO3

Zn

NO3

Cu

Zn2+

Cu2+Cl K+

e e

t hiu th ngoi theochiu ngc li.

ln ca hiu th tvo phi > +1,10 V

/c Cu s ha tan v Zns kt ta .

DC V+


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4.

QUY C vSC IN NG VTH IN CC (I.U.P.A.C, 1953)


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1) Nguyn t (pin) Galvani c biu din di dng s :

Zn Zn2+(a1) Cu2+(a2) Cu hay

Zn Zn2+(a1) Cu2+(a2) Cu (*)

Pin Daniel

Ranh gii phn pha: Tip xc dung dch :

Ranh gii khng c th tip xc dung dch :


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(-) Zn (s )ZnSO4(aq ) CuSO4(aq )Cu (s ) (+)

Zn (s )ZnSO4(aq ) CuSO4(aq )Cu (s )

Hnh thnh th tip xc dung dch/dung dch gia 2 ngn

Trit tiu th tip xc dung dch/dung dch gia 2 ngn

2. Sc in ng ca nguyn t Galvani


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Sbng hiu ca th in cc bn

phi trong s (xy ra phn ng kh)

tr th in cc bn tri s (xy ra

phn ng oxyha); hay:

Epin= Ephi (catod) - Etri (anod)

g g y

cm

dd

cm

dd Thtipxc giadung dch

v cumui, thtipxc s

trittiu khi tnh S

3. Phn ng trong nguyn

t


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g g g y


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4) Th in cc ca bn pin, th d


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Zn2+Zn (a)

Cu2+Cu (b)

5)in cc hydro:

Pt,H2(PH2) | H+(aH+)

Th ca in cc hydro vi p sut ring

phn ca kh hydro bng 1 bar v hot ion H+ bng 1 c quy c bng 0

mi nhit .

in cc H tiu chun:

(k hiu: SHE hoc NHE)0o

2/ HHE

Th in cc


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l sc in ng ca cc pin c in cc bn phi (trong

s ) l bn pin v in cc bn tri l in cchydro tiu chun:

(Pt) H2(1 bar)H+(a= 1)Zn2+Zn (a)

(Pt) H2(1 bar)H+(a= 1)Cu2+Cu (b)

vi phn ng trong pin xy ra theo chiu :

H2 + Zn2+ H+ + Zn (a)

H2 + Cu2+ H+ + Cu (b)

Th in cc


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o th in cc tiu chun


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19.3

Zn (s) | Zn2+(1 M) || H+(1 M) | H2(1 atm) | Pt (s)

E0 = E0cathodeE0anode

E0 = 0.76 V E0 = 0.34 V


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E0 l th kh chun ( phn ngkh)

E0 cng dng th cht oxyha c tnh oxy ha mnh

Bn phn ng thun nghch

Gi tr E0 khng thay i khithay i h s t lng

Tm tt


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Nguyn t galvani c to thnh t hai in cc (bn pin):anod v catod; trn catod xy ra phn ng kh, cn trn anod

phn ng oxy ha. Trong s , in cc anod c vit bn tri, in cc catod

c vit bn phi.

Nu loi tr th tip xc gia cc pha lng th sc in ng

ca nguyn t galvani bng hiu ca th in cc bn phi s (catod) tr i th in cc bn tri s (anod).

Th in cc l sc in ng ca nguyn t c in cc bnphi (trong s ) l bn pin v in cc bn tri l in cc

hydro tiu chun.

Th ca in cc hydro tiu chun c quy c bng 0 minhit .


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5.

PHN LOI IN CC

PHN LOI IN CC


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in cc Calomel


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2-0

oo

o

)(-

)(

-

)(22

][Clln

2F

RTEE

log0.059EE;lnEE

(S.H.E)mV268E

Cl2Hg2e2ClHg

-Cl-Cl

aa

nF

RT

aqlr


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.6PHN LOI PIN IN HA


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Pin Nng


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- C th khng ti ionhoc c ti ion.

- Hiu th khong vi chc n vi trm mV, c ng dng thc

t.- Hin din nhiu trong c th sng y sinh (Nobel HH 1997)

- Rt a dng trong ng dng phn tch ha hc, y sinh, mitrng, (u d cc loi)

Nobel Ha hc 1997: 1/2 cho Paul D. Boyer and John E.Walker "enzymatic mechanism underlying the synthesis of

adenosine triphosphate (ATP)"; cho Jens C. Skou"forthe first discovery of an ion-transporting enzyme, Na+, K+-

ATPase".


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Mt s ngun in ph bin


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Pin s cp (Primary Batteries) : phn ng pin l btthun nghch pin khng sc.Pin th cp (Secondary Batteries): Phn ng pin lthun nghch pin sc

Hai loi pin in ha c bn

Pin s cp

Pi kh (L l h )


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Pin kh (Leclanche)

Pin

Pin leclanche kim

Acquy ch

Pin th cp - secondary batteries


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Acquy ch

Catod:

Anod:


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Pin liti


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Pin nhin liu


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