CHUYN 16 L THUYT V PP GII BI TP IN PHN

CHUYN 16 L THUYT V PP GII BI TP IN PHN

I KHI NIM
S in phn l qu trnh oxi ha kh xy ra b mt cc in cc khi c dng in mt chiu i qua cht in li
nng chy hoc dung dch cht in li
- S in phn l qu trnh s dng in nng to ra s bin i ha hc
- Trong qu trnh in phn, di tc dng ca in trng cc cation chy v cc m (catot) cn cc anion chy v
in cc dng (anot), ti xy ra phn ng trn cc in cc (s phng in)
- Ti catot xy ra qu trnh kh cation (Mn+ + ne M) cn ti anot xy ra qu trnh oxi ha anion (Xn- X + ne)
- Ngi ta phn bit: in phn cht in li nng chy, in phn dung dch cht in li trong nc, in phn dng
in cc dng tan
II S IN PHN CC CHT IN LI
1. in phn cht in li nng chy
Trong thc t, ngi ta thng tin hnh in phn nhng hp cht (mui, baz, oxit) nng chy ca cc kim loi c
tnh kh mnh nh Li, Na, K, Ba, Ca, Mg, Al
V d 1: in phn NaCl nng chy c th biu din bng s :
Catot ( )
2| Na+ + e Na

NaCl

Anot ( + )
2Cl- Cl2 + 2e

Phng trnh in phn l: 2NaCl

2Na + Cl2
Cn c mng ngn khng cho Cl2 tc dng tr li vi Na trng thi
nng chy lm gim hiu sut ca qu trnh in phn. Mt s cht
ph gia nh NaF, KCl gip lm gim nhit nng chy ca h
V d 2: in phn NaOH nng chy c th biu din bng s :
Catot ( )
NaOH
4OH- O2 + 2H2O + 4e

4| Na+ + 1e Na
Phng trnh in phn l: 4NaOH

Anot ( + )

4Na + O2 + 2H2O

V d 3: in phn Al2O3 nng chy pha thm criolit (Na3AlF6) c th biu din bng s :
Catot ( )
4| Al3+ + 3e Al
Phng trnh in phn l: 2Al2O3

Al2O3

Anot ( + )
3| 2O2- O2 + 4e

4Al + 3O2
Criolit (Na3AlF6) c vai tr quan trng nht l lm gim nhit nng
chy ca Al2O3 t 2050oC xung khong 900oC, ngoi ra n cn lm tng
dn in ca h v to lp ngn cch gia cc sn phm in phn v
mi trng ngoi. Anot lm bng than ch th in cc b n mn dn do
chng chy trong oxi mi sinh: C + O2
2CO

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CO2 v 2C + O2

CHUYN 16 L THUYT V PP GII BI TP IN PHN

2. in phn dung dch cht in li trong nc
Trong s in phn dung dch, ngoi cc ion do cht in li phn li ra cn c cc ion H + v OH- ca nc. Do vic
xc nh sn phm ca s in phn phc tp hn. Ty thuc vo tnh kh v tnh oxi ha ca cc ion c trong bnh
in phn m ta thu c nhng sn phm khc nhau.
V d khi in phn dung dch NaCl, cc ion Na+, H+(H2O) chy v catot cn cc ion Cl-, OH-(H2O) chy v anod. Ion
no trong s chng s phng in cc in cc.
C s gii quyt vn ny l da vo cc gi tr th oxi ha kh ca cc cp. Trong qu trnh in phn, trn
catot din ra s kh. V vy khi c nhiu dng oxi ha th trc ht dng oxi ha ca cp c th ln hn s b kh
trc. Ngc li trn anot s din ra s oxi ha dng kh ca cp c th oxi ha kh nh nht trc.
a) Kh nng phng in ca cc cation catot: catot c th xy ra cc qu trnh kh sau y:
- Mn+ + ne M
- 2H+(axit) + 2e H2
- Hoc ion hiro ca nc b kh: 2H2O + 2e H2 + 2OHDng oxi ha ca nhng cp c th cng ln cng d b kh. Theo dy th oxi ha kh th kh nng b kh ca cc
ion kim loi nh sau:
- Cc cation t Zn2+ n cui dy Hg2+, Cu2+, Fe3+, Ag+d b kh nht v th t tng dn
- T Al3+ n cc ion u dy Na+, Ca2+, K+khng b kh trong dung dch
- Cc ion H+ ca axit d b kh hn cc ion H+ ca nc
b) Kh nng phng in ca cc anion anot: anot xy ra qu trnh oxi ha cc anion gc axit nh Cl -, S2-hoc
ion OH- ca baz kim hoc nc
- 2Cl- Cl2 + 2e
- 4OH- O2 + 2H2O + 4e
- Hoc ion OH- ca nc b oxi ha: 2H2O O2 + 4H+ + 4e
Dng kh ca nhng cp c th oxi ha kh cng nh cng d b oxi ha. Theo dy th oxi ha kh th kh nng b
oxi ha ca cc anion nh sau:
- Cc anion gc axit khng cha oxi d b oxi ha nht theo th t: RCOO - < Cl- < Br- < I- < S2-
- Cc anion gc axit nh NO3-, SO42-, PO43-, CO32-, ClO4-khng b oxi ha
- Ring cc ion OH- ca kim hoc ca nc kh b oxi ha hn cc ion S2-, I-, Br-, Cl-
- Nu khi in phn khng dng cc anot tr nh graphit, platin (Pt) m dng cc kim loi nh Ni, Cu, Agth cc
kim loi ny d b oxi ha hn cc anion v th oxi ha kh ca chng thp hn, v do chng tan vo dung dch
(anot tan)
c) Mt s v d:
- in phn dung dch CuCl2 vi anot tr c th biu din bng s :
Catot ( )
Cu2+ + 2e
Cu

CuCl2

Anot ( + )
2ClCl2 + 2e

Phng trnh in phn l: CuCl2

Cu + Cl2
- in phn dung dch K2SO4 vi anot tr c th biu din bng s :
Catot ()
K2SO4
+
H2O, K
(H2O)
2| 2H2O + 2e
H2 + 2OH-

Anot (+)
H2O, SO422H2O
O2 + 4H+ + 4e

Phng trnh in phn l: 2H2O

2H2 + O2
- in phn dung dch NaCl bo ha vi in cc tr c mng ngn c th biu din bng s :

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CHUYN 16 L THUYT V PP GII BI TP IN PHN

Catot ( )
NaCl
H2O, Na+
(H2O)
2H2O + 2e
H2 + 2OHPhng trnh in phn l: 2NaCl + 2H2O

Anot ( + )
Cl-, H2O
2ClCl2 + 2e

2NaOH + H2 + Cl2

Nu khng c mng ngn th: Cl2 + 2NaOH

NaCl + NaClO + H2O nn phng trnh in phn l: NaCl + H2O

NaClO + H2
- in phn dung dch NiSO4 vi anot tr c th biu din bng s :
Catot ( )
Ni2+, H2O
2+
2| Ni + 2e
Ni

NiSO4
(H2O)

Anot ( + )
H2O, SO422H2O
O2 + 4H+ + 4e

Phng trnh in phn l: 2NiSO4 + 2H2O

2Ni + 2H2SO4 + O2
- in phn dung dch NiSO4 vi anot bng Cu c th biu din bng s :
Catot ( )
Ni2+, H2O
2+
Ni + 2e
Ni

NiSO4
(H2O)

Cu ( + )
H2O, SO42Cu
Cu2+ + 2e

Phng trnh in phn l: NiSO4 + Cu

CuSO4 + Ni
- in phn dung dch CuSO4 vi anot bng Cu (nh hnh v sau y):
catot ( ): Cu2+(dd) + 2e
Cu lm gim nng ion Cu2+ bn nhnh tri ca ng
ch U
anot ( + ): Cu(r)
Cu2+(dd) + 2e lm tng nng ion Cu2+ bn nhnh tri ca
ng ch U v anot dn dn b ha tan
Phng trnh in phn l: Cu(r) + Cu2+(dd)
Cu2+(dd) + Cu(r)
- in phn dung dch hn hp cha FeCl3, CuCl2 v HCl vi anot tr c th biu
din bng s :
Catot ( )
3+

2+

Fe , Cu , H

FeCl3, CuCl2, HCl

Anot ( + )

2| Fe3+ + 1e Fe2+
Cu2+ + 2e
Cu
+
2H + 2e
H2
Fe2+ + 2e
Fe

2Cl-

Cl2 + 2e

Qu trnh in phn ln lt xy ra cc in cc l:
2FeCl3

2FeCl2 + Cl2

CuCl2

Cu + Cl2

2HCl

H2 + Cl2

FeCl2

Fe + Cl2

III NH LUT FARADAY

Khi lng cht gii phng mi in cc t l vi in lng i qua dung dch v ng lng ca cht

m=

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CHUYN 16 L THUYT V PP GII BI TP IN PHN

Trong :
- m: khi lng cht gii phng in cc (gam)
- A: khi lng mol nguyn t ca cht thu c in cc
- n: s electron m nguyn t hoc ion cho hoc nhn
- I: cng dng in (A)
- t: thi gian in phn (s)
- F: hng s Faraday l in tch ca 1 mol electron hay in lng cn thit 1 mol electron chuyn di trong mch
catot hoc anot (F = 1,602.10-19.6,022.1023 96500 C.mol-1)
-

: ng lng gam ha hc

Biu thc lin h: Q = I.t = 96500.ne

ne =

(ne l s mol electron trao i in cc)

V d: in phn 100 ml dung dch NaCl vi in cc tr c mng ngn vi cng dng in I = 1,93A. Dung
dch thu c sau khi in phn c pH = 12. Bit th tch dung dch khng i, clo khng ha tan trong nc v hiu
sut in phn 100%. Thi gian tin hnh in phn l:
A. 50 s
B. 60 s
C. 100 s
D. 200 s
Gii:
pH = 12

[OH-] = 10-2

nOH- = 10-3 M

Ti catot () xy ra phn ng: 2H2O + 2e

hoc

mH2 = 10-3 gam

H2 + 2OH-

t=

ne = 10-3 mol
= 50 s

t=

= 50 s

p n A

IV - NG DNG CA IN PHN
S in phn c nhiu ng dng trong cng nghip
1. iu ch cc kim loi (xem bi iu ch cc kim loi)
2. iu ch mt s phi kim nh H2, O2, F2, Cl2
3. iu ch mt s hp cht nh NaOH, H2O2, nc Gia ven
4. Tinh ch mt s kim loi nh Cu, Pb, Zn. Fe. Ag, Au
5. M in

in phn vi anot tan cng c dng trong m in, nhm bo v kim loi khi b n
mn v to v p cho vt m. Anot l kim loi dng m (nh hnh v l vng) cn
catot l vt cn m (ci tha). Lp m thng rt mng, c dy t 5.10 -5 1.10-3 cm

Phng php gii bi tp v in phn

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CHUYN 16 L THUYT V PP GII BI TP IN PHN

I NHC LI L THUYT
1) in phn cht in li nng chy: p dng i vi MCln, M(OH)n v Al2O3 (M l kim loi nhm IA v
IIA)
2) in phn dung dch cht in li trong nc:
- Vai tr ca nc: trc ht l dung mi ha tan cc cht in phn, sau c th tham gia trc tip vo qu
trnh in phn:
+ Ti catot (cc m) H2O b kh: 2H2O + 2e H2 + 2OH
+ Ti anot (cc dng) H2O b oxi ha: 2H2O O2 + 4H+ + 4e
- Ti catot (cc m) xy ra qu trnh kh M+, H+ (axit), H2O theo quy tc:
+ Cc cation nhm IA, IIA, Al3+ khng b kh (khi H2O b kh)
+ Cc ion H+ (axit) v cation kim loi khc b kh theo th t trong dy th in cc chun (ion c tnh oxi
ha mnh hn b kh trc): Mn+ + ne M
+ Cc ion H+ (axit) d b kh hn cc ion H+ (H2O)

+ V d khi in phn dung dch hn hp cha FeCl3, CuCl2 v HCl th th t cc ion b kh l: Fe3+ + 1e
Fe2+ ; Cu2+ + 2e Cu ; 2H+ + 2e H2 ; Fe2+ + 2e Fe
- Ti anot (cc dng) xy ra qu trnh oxi ha anion gc axit, OH (baz kim), H2O theo quy tc:
+ Cc anion gc axit c oxi nh NO3, SO42, PO43, CO32, ClO4khng b oxi ha
+ Cc trng hp khc b oxi ha theo th t: S2 > I > Br > Cl > RCOO > OH > H2O
3) nh lut Faraday

m=
Trong :
+ m: khi lng cht gii phng in cc (gam)
+ A: khi lng mol ca cht thu c in cc
+ n: s electron trao i in cc
+ I: cng dng in (A)
+ t: thi gian in phn (s)
+ F: hng s Faraday l in tch ca 1 mol electron hay in lng cn thit 1 mol electron chuyn di
trong mch catot hoc anot (F = 1,602.10-19.6,022.1023 96500 C.mol-1)
II MT S C S GII BI TP V IN PHN
- Khi lng catot tng chnh l khi lng kim loi to thnh sau in phn bm vo
- m (dung dch sau in phn) = m (dung dch trc in phn) (m kt ta + m kh)
- gim khi lng ca dung dch: m = (m kt ta + m kh)
- Khi in phn cc dung dch:
+ Hiroxit ca kim loi hot ng ha hc mnh (KOH, NaOH, Ba(OH)2,)
+ Axit c oxi (HNO3, H2SO4, HClO4,)
+ Mui to bi axit c oxi v baz kim (KNO3, Na2SO4,)
Thc t l in phn H2O cho H2 ( catot) v O2 ( anot)
- Khi in phn dung dch vi anot l mt kim loi khng tr (khng phi Pt hay in cc than ch) th ti
anot ch xy ra qu trnh oxi ha in cc
- C th c cc phn ng ph xy ra gia tng cp: cht to thnh in cc, cht tan trong dung dch, cht
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CHUYN 16 L THUYT V PP GII BI TP IN PHN

dng lm in cc. V d:
+ in phn nng chy Al2O3 (c Na3AlF6) vi anot lm bng than ch th in cc b n mn dn do
chng chy trong oxi mi sinh
+ in phn dung dch NaCl khng mng ngn to ra nc Giaven v c kh H2 thot ra catot
+ Phn ng gia axit trong dung dch vi kim loi bm trn catot
- Vit phn ng (thu hoc nhng electron) xy ra cc in cc theo ng th t, khng cn vit phng
trnh in phn tng qut
- Vit phng trnh in phn tng qut (nh nhng phng trnh ha hc thng thng) tnh ton khi
cn thit
- T cng thc Faraday s mol cht thu c in cc
- Nu bi cho I v t th trc ht tnh s mol electron trao i tng in cc (ne) theo cng thc: ne =
(*) (vi F = 96500 khi t = giy v F = 26,8 khi t = gi). Sau da vo th t in phn, so snh tng s
mol electron nhng hoc nhn vi ne bit mc in phn xy ra. V d d on xem cation kim
loi c b kh ht khng hay nc c b in phn khng v H2O c b in phn th in cc no
- Nu bi cho lng kh thot ra in cc hoc s thay i v khi lng dung dch, khi lng in
cc, pH,th da vo cc bn phn ng tnh s mol electron thu hoc nhng mi in cc ri thay
vo cng thc (*) tnh I hoc t
- Nu bi yu cu tnh in lng cn cho qu trnh in phn th p dng cng thc: Q = I.t = ne.F
- C th tnh thi gian t cn in phn ht mt lng ion m bi cho ri so snh vi thi gian t trong
bi. Nu t < t th lng ion b in phn ht cn nu t > t th lng ion cha b in phn ht
- Khi in phn cc dung dch trong cc bnh in phn mc ni tip th cng dng in v thi gian
in phn mi bnh l nh nhau s thu hoc nhng electron cc in cc cng tn phi nh nhau v
cc cht sinh ra cc in cc cng tn t l mol vi nhau
- Trong nhiu trng hp c th dng nh lut bo ton mol electron (s mol electron thu c catot = s
mol electron nhng anot) gii cho nhanh
III MT S V D MINH HA
V d 1: in phn ha ton 2,22 gam mui clorua kim loi trng thi nng chy thu c 448 ml kh (
ktc) anot. Kim loi trong mui l:
A. Na
B. Ca
C. K
D. Mg
Hng dn: nCl2 = 0,02
Ti catot: Mn+ + ne M Theo lbt khi lng mM = m(mui) m(Cl2) = 2,22 0,02.71 = 0,8 gam
Ti anot: 2Cl Cl2 + 2e Theo lbt mol electron ta c nM =
(hoc c th vit phng trnh in phn MCln

M = 20.n n = 2 v M l Ca

M + n/2Cl2 tnh) p n B

V d 2: Tin hnh in phn (vi in cc Pt) 200 gam dung dch NaOH 10 % n khi dung dch NaOH
trong bnh c nng 25 % th ngng in phn. Th tch kh ( ktc) thot ra anot v catot ln lt l:
A. 149,3 lt v 74,7 lt
B. 156,8 lt v 78,4 lt
C. 78,4 lt v 156,8 lt
D. 74,7 lt v 149,3 lt
Hng dn: mNaOH (trc in phn) = 20 gam
in phn dung dch NaOH thc cht l in phn nc: H2O 1/2 O2 (anot) + H2 (catot) NaOH khng
i m (dung dch sau in phn) = 80 gam m (H2O b in phn) = 200 80 = 120 gam nH2O =
20/3 mol VO = 74,7 lt v VH = 149,3 lt p n D

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CHUYN 16 L THUYT V PP GII BI TP IN PHN

V d 3: Sau mt thi gian in phn 200 ml dung dch CuSO4 ( d = 1,25 g/ml) vi in cc graphit (than
ch) thy khi lng dung dch gim 8 gam. lm kt ta ht ion Cu2+ cn li trong dung dch sau in
phn cn dng 100 ml dung dch H2S 0,5 M. Nng phn trm ca dung dch CuSO4 ban u l:
A. 12,8 %
B. 9,6 %
C. 10,6 %
D. 11,8 %
Hng dn: nH2S = 0,05 mol
- Gi x l s mol CuSO4 tham gia qu trnh in phn: CuSO4 + H2O Cu + 1/2O2 + H2SO4 (1) m (dung
dch gim) = m Cu(catot) + m O2(anot) = 64x + 16x = 8 x = 0,1 mol - CuSO4 + H2S CuS + H2SO4 (2)
nH2S = nCuSO4 = 0,05 mol
- T (1) v (2) nCuSO4 (ban u) = 0,1 + 0,05 = 0,15 (mol) C% =
p n B
V d 4: in phn 100 ml dung dch CuSO4 0,2 M vi cng dng in 9,65A. Tnh khi lng Cu bm
vo catot khi thi gian in phn t1 = 200 s v t2 = 500 s. Bit hiu sut in phn l 100 %
A. 0,32 gam v 0,64 gam
B. 0,64 gam v 1,28 gam
C. 0,64 gam v 1,60 gam
D. 0,64 gam v 1,32 gam
Hng dn: nCuSO4 = 0,02 = nCu2+
Thi gian cn thit in phn ht Cu2+ l t =
s t1 < t < t2 Ti t1 c 1/2 s mol
Cu2+ b in phn m1 = 0,01.64 = 0,64 gam v ti t2 Cu2+ b in phn ht m2 = 1,28 gam p n
B
V d 5: in phn 200 ml dung dch CuSO4 vi in cc tr v cng dng in 1A. Khi thy catot
bt u c bt kh thot ra th dng in phn. trung ha dung dch thu c sau khi in phn cn dng
100 ml dung dch NaOH 0,1M. Thi gian in phn v nng mol ca dung dch CuSO4 ban u l:
A. 965 s v 0,025 M
B. 1930 s v 0,05 M
C. 965 s v 0,05 M
D. 1930 s v 0,025 M
Hng dn: nNaOH = 0,01 mol
- Khi catot bt u c bt kh (H2) thot ra chng t CuSO4 b in phn ht theo phng trnh:
CuSO4 + H2O Cu + 1/2O2 + H2SO4
- nNaOH = nOH = 0,01 mol nH2SO4 = 0,5.nH+ = 0,5.nOH = 0,005 (mol) nCu = nCuSO4 = 0,005
(mol)
= 0,005 t = 965 s v CM(CuSO ) =
thu hoc nhng electron in cc tnh) p n A

M (hoc c th da vo cc phn ng

V d 6: in phn 200 ml dung dch hn hp AgNO3 0,1 M v Cu(NO3)2 0,2 M vi in cc tr v cng

dng in bng 5A. Sau 19 pht 18 giy dng in phn, ly catot sy kh thy tng m gam. Gi tr ca
m l:
A. 5,16 gam
B. 1,72 gam
C. 2,58 gam
D. 3,44 gam
Hng dn: nAg+ = 0,02 mol ; nCu2+ = 0,04 mol
- Ta c ne =
mol
- Th t cc ion b kh ti catot:
Ag+ + 1e Ag (1) sau (1) cn 0,06 0,02 = 0,04 mol electron
0,02 0,02 0,02
Cu2+ + 2e Cu (2) sau (2) cn d 0,02 mol Cu2+
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CHUYN 16 L THUYT V PP GII BI TP IN PHN

0,02 0,04
0,02
m (catot tng) = m (kim loi bm vo) = 0,02.(108 + 64) = 3,44 gam p n D
V d 7: Ha tan 50 gam tinh th CuSO4.5H2O vo 200 ml dung dch HCl 0,6 M thu c dung dch X.
em in phn dung dch X (cc in cc tr) vi cng dng in 1,34A trong 4 gi. Khi lng kim
loi thot ra catot v th tch kh thot ra anot ( ktc) ln lt l (Bit hiu sut in phn l 100 %):
A. 6,4 gam v 1,792 lt
B. 10,8 gam v 1,344 lt
C. 6,4 gam v 2,016 lt
D. 9,6 gam v 1,792 lt
Hng dn: nCuSO4.5H2O = nCuSO4 = 0,2 mol ; nHCl = 0,12 mol
- Ta c ne
= mol
- Th t in phn ti catot v anot l:
Ti catot: Cu2+ + 2e Cu Cu2+ cha b in phn ht m (kim loi catot) = 0,1.64 = 6,4 gam
0,1
0,2
0,1
Ti anot:
2Cl Cl2 + 2e ne (do Cl nhng) = 0,12 < 0,2 mol ti anot Cl b in phn ht v
0,12 0,06 0,12
n nc b in phn ne (do H2O nhng) = 0,2 0,12 = 0,08 mol
2H2O O2 + 4H+ + 4e
0,02
0,08
V (kh thot ra anot) = (0,06 + 0,02).22,4 = 1,792 lt p n A
V d 8: C 200 ml dung dch hn hp Cu(NO3)2 v AgNO3, in phn ht ion kim loi trong dung dch
cn dng cng dng in 0,402A trong 4 gi. Sau khi in phn xong thy c 3,44 gam kim loi bm
catot. Nng mol ca Cu(NO3)2 v AgNO3 trong hn hp u ln lt l:
A. 0,2 M v 0,1 M
B. 0,1 M v 0,2 M
C. 0,2 M v 0,2 M
D. 0,1 M v 0,1 M
Hng dn:
- Ta c ne =
- Ti catot: Ag+ + 1e Ag

mol

x
x (mol)
Cu2+ + 2e Cu
y
y (mol)

Ta c h phng trnh:

CM Cu(NO3)2 = CM AgNO3 = 0,1 M p n D

V d 9: Ha tan 4,5 gam tinh th MSO4.5H2O vo nc c dung dch X. in phn dung dch X vi in
cc tr v cng dng in 1,93A. Nu thi gian in phn l t (s) th thu c kim loi M catot v
156,8 ml kh ti anot. Nu thi gian in phn l 2t (s) th thu c 537,6 ml kh . Bit th tch cc kh o
ktc. Kim loi M v thi gian t ln lt l:
A. Ni v 1400 s
B. Cu v 2800 s
C. Ni v 2800 s
D. Cu v 1400 s
Hng dn: Gi nMSO4 = nM2+ = x mol

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CHUYN 16 L THUYT V PP GII BI TP IN PHN

V d 10: Mc ni tip hai bnh in phn: bnh (1) cha dung dch MCl2 v bnh (2) cha dung dch
AgNO3. Sau 3 pht 13 giy th catot bnh (1) thu c 1,6 gam kim loi cn catot bnh (2) thu c 5,4
gam kim loi. C hai bnh u khng thy kh catot thot ra. Kim loi M l:
A. Zn
B. Cu
C. Ni
D. Pb
Hng dn: - Do hai bnh mc ni tip nn ta c:
Q = I.t =

M = 64 Cu p n B

V d 11: in phn nng chy Al2O3 vi anot than ch (hiu sut in phn 100 %) thu c m kg Al
catot v 67,2 m3 ( ktc) hn hp kh X c t khi so vi hiro bng 16. Ly 2,24 lt ( ktc) hn hp kh X
sc vo dung dch nc vi trong (d) thu c 2 gam kt ta. Gi tr ca m l:
A. 54,0 kg
B. 75,6 kg
C. 67,5 kg
D. 108,0 kg
Hng dn: 2Al2O3

4Al + 3O2 (1) ; C + O2

CO2 (2) ; 2C + O2

2CO (3)

- Do X = 32 hn hp X c CO2 ; CO (x mol) v O2 d (y mol)

- 2,24 lt X + Ca(OH)2 d 0,02 mol kt ta = nCO2 trong 67,2 m3 X c 0,6 CO2
- Ta c h phng trnh:
T (1) ; (2) ; (3) mAl =

v 0,6 + x + y = 3 x = 1,8 v y = 0,6

kg p n B

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