Download - Nguyên tố Ganvani và cân bằng điện cực
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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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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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