Post on 09-Oct-2015
5/19/2018 3.2. Chng 4. S V n Chuy n i n Tch - D n i n Trong Dd i n Ly_4T_RR
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CHNG 4
S VN CHUYN IN TCH
DN iN
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Ni dung
4.1. Khi nim c bn4.2. dn in
4.3. Linh ion v linh ion H+- OH-
4.4. dn in ca dung dch in ly trong dung mi khc
4.5. S chuyn vn ca cc ion
4.6. Phng php o dn in v ng dng
4.7. Bi tp
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Vt th cng loi
4.1. Khi nim c bn
4.1.1. Vn chuyn in tch
Ionion
in t - in t
Thay i thnh phn ha hc
Khi dn in, ti b mt tip xc
Phn ng ha hc xy ra
Vt th khc loi
Ionin t
in t - ion
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Nhng dung dch in ly,
cht in ly nng chy, cckh ion ha.
Dn in do s chuyn vn
ca cc ion.
4.1.2. Phn loi dy dn
Da vo bn cht dn in,
FARADAY chia thnh 2 loi
Dy dn loi 1 Dy dn loi 2
Nhng dy lm bng kim loi
(ng, bc, nhm) hay bndn.
Dn in do s dch chuyn ca
cc in t (electron) v l trng
4.1. Khi nim c bn
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Cc m (Catod)
+ Electron chuyn t in cc (ni
cc M ngun in) n ion(trong dung dch)
+ Phn ng kh xy ra
Cu2+ + 2e = Cu
Fe3+ + e = Fe2+
2H2O + 2e = H2 + 2OH-
Cc dng (anod)
+ Electron chuyn t ion (trong
dung dch) n in cc (nicc DNG ngun in)
+ Phn ng kh xy ra
4OH- = O2 + 2H2O + 4e
Fe2+ = Fe3++ e
Zn = Zn2+ + 2e
4.1.3. S in phn
4.1. Khi nim c bn
Tngqu trnh
Dy dn loi 1(ANOD)
Dy dnloi2
Dy dnloi2 (CATOD)
q
q
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Trong :q : in lng i qua dung dch cht in ly (culng)I : cng dng in (A)
t : thi gian (s)k0: h s t l = /F
Lng cht thot ra hay bm ln b mt in
cc khi in phn, t l thun vi in lng i
qua dung dch .
m = k0.I.t = k0.q
4.1.4.nh lut Faraday
4.1. Khi nim c bn
nh lut Faraday 1
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nh lut Faraday 1
4.1.4.nh lut Faraday
4.1. Khi nim c bn
chuynha mtnglnggamcamtchtbtkbnginphn cnmtinlngbngchnh sFARADAY.
Cho inlng1F qua th thu c1 lg
V k0= /FNn q = 1F m = k0x1F = ng lng in ha)
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nh lut Faraday 1
4.1.4.nh lut Faraday
4.1. Khi nim c bn
Cu 179183
Bi tp:
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Khi cho cng mt in lng i qua cc dung
dch in ly khc nhau th lng cht thot ra
hay bm ln trn b mt in cc t l ving lng in ha ca n.
nh lut Faraday 2
4.1.4.nh lut Faraday
4.1. Khi nim c bn
Cu 178Bi tp:
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1C (culong) = 1 ampe.giy
1F = 26,8 ampe.gi = 96484,520 96500 C
4.1.4.nh lut Faraday
4.1. Khi nim c bn
Mt s chuyn i n v
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4.2. dn in
4.2.1. dn in ring
dn in ring ( -1.cm-1)
L dnincamtdung dchc thtch
V = 1cm3, ctgiahai inccphngsong
song c din tch nhnhau (cm2) v cch nhau 1
cm.
- in tr ring, in trca dy dn di 1cm, tit
din 1cm2
.
1
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sR;
R
1L
Mt s cng thc quan h
4.2. dn in
4.2.1. dn in ring
t:
s
k : hng s bnh in cc.
L.k
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L dnincamt th tch tnh theo cm3
changmtng lng gam chtin ly
nmgia hai incc phng song song cch
nhau 1cm.
dn in ng lng (cm2/lg. )
4.2. dn in
4.2.2. dn in ng lng
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Trong :
CN : nng ng lng
: dn in ng lng (cm2. -1.lg-1)
Cng thc tnh:
4.2. dn in
4.2.2. dn in ng lng
NC1000.
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4.6. PP o dn in - ng dng
4.6.1. Phng php o dn in
in trcadung dchKCl 0,02N 25oC trong mtbnh o
dninocl 457. Bitdninring cadung dch
l 0,0028 -1.cm-1. Dng bnh ny odnincadung dch
CaCl2cha0,555g CaCl2trong 1 lt c gi trl 1050. Xc nh
dninnglngcadung dchCaCl2?
V d1
Cu 233 238Bi tp:
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: dn in ng lng gii hn (dung dch v cng long)
A : gi tr thc nghim. Ph thuc T, P, dung mi, cht in ly
i vi cht in ly mnh, thch hp PT thc nghim Kohlrausch:
4.2. dn in
4.2.2. dn in ng lng
Trong :
nh lut th nhtKohlrausch
CA-
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i vi cht in ly mnh (= 1)
Vi cht in ly yu khi dung dch v cng long:
i vi cht in ly yu:
, +, -: dn in ng lng ti hn cc ion vi
dung dch v cng long (cm2/.lg)
4.2. dn in
4.2.2. dn in ng lng
Trong :
nh lut th haiKohlrausch
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4.2. dn in
4.2.2. dn in ng lng
Bit dnin ng lng gii hn 250C ca dung dch
HCl; CH3COONa v NaCl ln lt l 426,1; 91 v 126,5
cm2/.lg. Tnh caCH3COOH nhittrn?
V d2
Cu 160
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4.2. dn in
4.2.2. dn in ng lng
dninng lnggiihn250C cadung dch trong
nc C2H5COONa, NaCl v HCl ln lt l 85,9; 126,45 v
425,15 cm2/.lg.
a. Tnh caaxt propionic nhittrn?
b. Xc nhnngH+nubitdninnglngcaaxt ny bng41,3 cm2/.lg?
V d3
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4.2. dn in
4.2.2. dn in ng lng
i vi cht in ly yu:
Kho st qu trnh phn ly:
AB = A+ + B-
Ta c hng s phn ly nh sau:
C.
K2
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4.2. dn in
4.2.2. dn in ng lng
Quan h gia - C
Cht in ly mnh (PT thc nghim Kohlrausch):
Cht in ly yu (1 1), phng trnh nghim ng:
CA-
cK.
12
.C
1
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4.2. dn in
4.2.2. dn in ng lng
nh lut gii hn Debye - Huckel
nh lut gii hn Debye Huckel v h s hot (hay phng
trnh gn ng bc nht):
Phng trnh gii hn ca h s hot trung bnh c dng:
cI.l
2ii Z.Ag
cI..l ZZ.Ag
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4.2. dn in
4.2.2. dn in ng lng
nh lut gii hn Debye - Huckel
cI.l
2ii Z.Ag
Nu dng nng molan, khi dung dch long Ci= mi.o
cI..l ZZ.Ag
mI.l
2ii Z'.Ag
mI..l ZZ'.Ag
250C, A = 0,509
o.A'A
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4.2. dn in
4.2.2. dn in ng lng
nh lut gii hn Debye - Huckel
250
C, s gn ng bc hai c dng
I.B.1
I.l
aZ.Ag
2ii
I.B.1
I.l
aZ.Z.Ag
I1
I.l
2ii Z.AgI1
I.l
Z.Z.Ag
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4.2. dn in
4.2.2. dn in ng lng
nh lut gii hn Debye - Huckel
Khi nng dung dch ln hn, vt qu nng gii hn ca nhlut gii hn (Pt gn ng bc hai):
250C:ang knh hu hiu trung bnh ion
A = 0,509 mol-1/2.dm-1/2
B = 0,329.107dm1/2.mol-1/2.nm-1
I.B.1
I.l
a
Z.Ag2ii
I.B.1
I.l
a
Z.Z.Ag
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4.2. dn in
4.2.2. dn in ng lng
Phng trnh Onsager
i vi cht in ly 2 1 trong nc, PT Onsager c dng:
i vi cht in ly 1 1 trong nc, PT Debye Onsager:
C.,
C
.T.T.2/12/3
- thm in mi; - nht; c nng
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Linh ion chnh l tc tuyt ica cc ion, n vcm2/von.giy.
Gi: +, -l tc chuyn ng cc iono+, o-l tc tuyt i cc ion
Ta c:
4.3. Linh ion Linh ion H+- OH-
4.3.1. Khi nim
: Cng in trng
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p dng nh lut Ohm v kt hp mt s biu thc khc, ta c
kt qu cui cng:
4.3. Linh ion Linh ion H+- OH-
4.3.1. Khi nim
in ly mnh:
in ly yu:
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Linh ca cc ion trong dung dch nc thng c cng
ln khong 6.10-4 cm2/V.s
Ring linh ca H+v OH-rt ln:
+ H+: 36,3.10-4cm2/V.s
+ OH-: 20,5.10-4cm2/V.s
4.3. Linh ion Linh ion H+- OH-
4.3.2. Linh ion ca cc ion H+
v OH-
Nguyn nhn
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dn in ca cc dung dch khc dung mi nc c
xc nh qua cc i lng Cion, tc chuyn vn v bncht dung mi.
Thng thng dn in ca chng nhhn so vi trong
nc, l do phn ly thp. (ngoi l NH3trong HCN)
4.4. dn in trong cc dung mi khc
nc.
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4.5. S chuyn vn cc ion
4.5.1. Khi nim
L tsgiain lngmang bimt loi ion
no qua tit din ca cht in ly v tng
inlngiqua titdindung dchinly .
S chuyn vn cc ion (s ti)
i
ii
q
qt
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4.5. S chuyn vn cc ion
4.5.1. Khi nim
Trong dung dchchahai loiion gmcation v anion th:
vv
v
vv
v
qt
oo
o
vv
v
vv
v
qtoo
o
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4.5. S chuyn vn cc ion
Anod
(+)
Catod
(-)
+ + + + + +
_ _ _ _ _ _
+ + + + + +
_ _ _ _ _ _
+ + + + + +
_ _ _ _ _ _
Vng I Vng II Vng III
+ + + + + +
_ _ _ _ _ _
(A)
(B)
(C)
+ + + + + +_ _ _ _ _ _ + + + + + +_ _ _ _ _ _ + + + + + +_ _ _ _ _ _
+
_
+ + + + +
_ _ _ _ _
- -
- -
- -
+ +
+ +
+ +
Anolit Catolit
4.5.2. Phng php Hittorf xc nh s chuyn vn
Ta c:
5
v
v
n
n
o
o
c
a
M hnh phngphp Hittorf
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4.5. S chuyn vn cc ion
4.5.2. Phng php Hittorf xc nh s chuyn vn
Tnh ton theo phngphp Hittorf
ca
a
ca
a
oo
o
mm
m
nn
n
vv
vt
Svnchuyncacc ion cxc nhtheo quan hsau:
ca
c
ca
c
oo
o
mm
m
nn
n
vv
vt
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4.5. S chuyn vn cc ion
4.5.3. Phng php ranh gii di ng
M hnh phngphp
MA
MA
x
b
b
+
MAchtinly cnnghin cu
MAchtinly chth
Mz+tcchuynvnlnhnMZ+
Dung dch khng mu o s dichuynbngchskhc x.
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4.5. S chuyn vn cc ion
4.5.3. Phng php ranh gii di ng
Tnh ton theo phngphp ranh giidi ng
q
CFSxt
Svnchuyncacation cxc nhtheo quan hsau:
Trong : x : ranh giidi ng,cm.
S : dintch titdinbnh, cm2.
C : slgtrong 1 cm3dung dch.
Khi dung dchc nngln,chnh xc khng cao
t= 1t+
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4.6. PP o dn in - ng dng
4.6.1. Phng php o dn in
a
b
c
Rx R3
R2 R1d
N
G
Phng php cu Wheatstone
a
b
c
RxR3
R2 R1d
N
G
Hiu chnh in dung
Rc= 1/.C
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Ngi ta s dng cc bnh o o dn in, thay v o v S ca
in cc bnh th ngi ta o k = /S thng qua vic o in tr ca
cht bit chnh xc dn in ring. Sau , tnh nh sau:
4.6. PP o dn in - ng dng
4.6.1. Phng php o dn in
xR
kL.k
Ngita thngdng dung dchinly chunKCl
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4.6. PP o dn in - ng dng
4.6.1. Phng php o dn in
in trcadung dchKCl 0,02N 25oC trong mtbnh o
dninocl 457. Bitdninring cadung dch
l 0,0028 -1.cm-1. Dng bnh ny odnincadung dch
CaCl2cha0,555g CaCl2trong 1 lt c gi trl 1050. Xc nh
dninnglngcadung dchCaCl2?
V d1
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Trong in phn, tit kim nng lng v nng cao
cht lng sn phm.
Hm lng mui trong cc dung dch.
Xc nh bc axt
Xc nh ha tan
Php nh phn in dn trong phn tch.
4.6. PP o dn in - ng dng
4.6.2. ng dng php o dn
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4.6. PP o dn in - ng dng
4.6.2. ng dng php o dn
dn in ring ca dung dch AgCl bo ha 25oC bng
3,14.10-6-1.cm-1; dninring canccngnhittrn
l 1,60.10-6-1.cm-1. Bit dn in gii hn ca Ag+ v Cl- l
61,92 v 76,34 cm2/.lg. Xc nhho tan v tch s tan ca
AgCl 250C.
V d
Hngdn
Tnh AgCl; tnh AgCl
NC
1000. CN TAgCl = CAg+.CCl-
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4.6. PP o dn in - ng dng
4.6.2. ng dng php o dnPhp nhphn indn
H+
OH-
b
VNaOH
a
c
Na+
Cl-
ChunHCl bngNaOH
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4.6. PP o dn in - ng dng
4.6.2. ng dng php o dnPhp nhphn indn
ChunKCl bngAgNO3
Cl
b
a
c
NO3
Ag+
b'
K+
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4.7. BI TP