Chuong11- Dien Hoa

8/3/2019 Chuong11- Dien Hoa

1/29

CHNG 11


2/29

Phan ng oxy hoa kh (O K)

Phan ng trong o co s trao

oi electron gia cac nguyen tcua nhng nguyen to tham gia phan

ng lam thay oi so oxy hoa cac

nguyen to.


3/29

Qua trnh cho electron goi la quatrnh oxy hoa, chat cho electron goila chat kh(chat b oxy hoa).

V du:

Zn 2e' Zn+2 Qua trnh nhan electron goi la

qua trnh kh, chat nhan electron

goi la chat oxy hoa. V du:

Cu+2 + 2e ' Cu


4/29

Phn ng tng quat:

Qt oxh: hI ' OxI + neQt kh: OxII + ne ' hIIPt oxh kh: hI + OxII ' OxI +

KhII

Cap oxy hoa kh: OxI/KhI , OxII/KhII

Vdu:

Qt oxh: Zn ' Zn2+ + 2e

Qt kh: Cu2+ + 2e ' Cu

Pt oxh kh: Zn + Cu2+ Zn2+ + Cu

Pt phan t: Zn + CuSO4 ZnSO4 + Cu

Cap oxy hoa kh: Zn2+/Zn; Cu2+/Cu


5/29

Nguyen tac 1: Tong so electron cho cua chat kh

phai bang tong so electron chat oxyhoa nhan vao.

Cac bc tien hanh can bang. Bc 1: Xac nh s thay oi so oxy

hoa cua cac chat. Bc 2: Lap phng trnh electron ion,

vi he so sao cho ung qui tac tren.

Bc 3: Thiet lap phng trnh ion cua

phan ng.


6/29

Vdu:Al + CuSO4 p Al2(SO4)3 + Cu

Al - 3e p Al+3

Cu+2

+ 2e p Cu2Al + 3Cu+2 = 2Al+3 + 3Cu

2Al + 3CuSO4 p 2Al2(SO4)3 + 3Cu

X2

X3


7/29

Nguyen tac 2:

oi vi phan ng O K xay ra trongmoi trng acid neu dang Ox cua chatOx co cha nhieu nguyen t Oxy hn

dang kh cua no th phai them H+

vaove tr ai (dang Ox) va them nc vaove phai (dang kh).

Neu dang kh cua chat Kh cha t

nguyen t Oxy hn dang Ox cua no ththem nc vao ve tr ai (dang Kh) va H+

vao ve phai (dang Ox).

Thieu O ben nao, them H2O ben o,ben kia them H+


8/29

Vdu:

OHSOKKNOMnSOSOHKNOKMnO 242344224 p

p

p

32

2

4

2

5

NOeNO

MneMnO

OHMnHeMnO 22

4 485 p

p HNOOHeNO 22

322

OHSOKKNOMnSOSOHKNOKMnO

OHNOMnHNOMnO

242344224

2324

352352

352652

!

!

X2

X5


9/29

Nguyen tac 3:

Phan ng O K xay ra trong moitrng base, neu dang Ox cua chatOx cha nhieu Oxy hn dang kh th

phai them nc vao ve tr ai, OH-vao ve phai.

Neu dang Kh cua chat Kh cha t Oxyhn dang Ox cua no th phai themOH- vao ve trai, nc vao ve phai.

Thieu O ben nao them OH- ben o,ben kia la H

2

O.


10/29

Vdu:

X1

X2

OHKClCrOKKOHCrClKClO24233

p

! OHClOHeClO 636 23

OHCrOOHeCr 22

4

3 483 !

OHCrOClOHCrClO2

2

4

3

3522 !

OHCrOKKClKOHCrClKClO 24233 527102 !


11/29

Nguyen tac 4:

Phan ng O-K trong moi trngtrung tnh. Neu dang Ox cua chat Oxcha nhieu nguyen t Oxy hn

dang Kh cua no th phai themnc vao ve trai, OH- vao ve phai.

Neu dang Kh cua chat Kh cha tnguyen t Oxy hn dang Ox cua no

th phai them nc vao ve tr ai, H+vao ve phai.

Them nc ve trai het, ve phai:- +


12/29

Vdu:

X2

X3

KOHKNOMnOOHKNOKMnO p 32224

! OHMnOOHeMnO 423 224

! HNOOHeNO 22

322

! HOHNOMnOOHNOMnO 6832732

32224

! OHNOMnOOHNOMnO 23232

32224

KOHKNOMnOOHKNOKMnO 23232 32224 !


13/29

Phan ng O K va dongien

ieu kien bnh thng, phan ng O K xay racung mot ni th hoa nang se bien thanh nhietnang.

ieu kien ac biet phan ng O K xay ragian tiep hai ni khac nhau th hoa nang sebien thanh ien nang (qua day dan).e-

Chat kh

e-

e-

Cha

t oxhAnode Cathode

Mang ngan


14/29

Nguyen to galvanic(1780): La thiet b chuyen hoa

nang sang ien nang.Cau tao gom hai thanh kimloai, nhung trong dung dchmuoi cua no, noi vi

nhau qua si day dan kimloai.

Hai thanh kim loai nay mot

thanh co tnh kh manhhn e cho e mot thanh

Luigi Galvani (Italia)


15/29


16/29

Cathode (+), xay raqua trnh kh

Anode (-) , xay raqua trnh oxy hoa


17/29

ien cc kem:Zn 2e p Zn+2 goi la am cc (Cathode)

ien cc ong:Cu+2 + 2e p Cu goi la dng cc (Anode)

Tc la am cc xay ra qua trnh Oxy hoa,Zn la chat Kh. dng cc xay ra qua trnhkh, Cu la chat Ox.

Phng trnh cua galvanic:Zn+Cu+2 = Zn+2 + Cu

Ngi ta ky hieu nguyen to ganvanic:

Hay

Tong quat:

CuCuSOZnSOZn44

CuCuZnZn 22

IIIIII

MddMddMM


18/29

The ien cc N (V), hay con goi lathe Oxy hoa Kh, hay la ban thephan ng, la mot ai lng khong

the o tr c tiep, ma phai so sanhvi mot ien cc chuan. Ngi ta chon Hydro lam ien cc

chuan:

2H+(dd) + 2e p H2 (k), ien cc laplatinum.Quy c: N0H2 = 0 (V). (The ien cc

tuyet oi cua no c chng 4.4 4.6

V)


19/29

Phng trnh Nernst:

Kh ne p Ox, N

Vi a la hoat o. Hoat o cua cac kimloai tinh khiet (va ca long tinh khiet) coinh bang 1.

Vi dung dch that (s dung C) nhieto 298K, ta co (R=8.31, T=298,F=96500):

Kh

Ox

a

a

nF

RTln

0!NN

][

][lg

059.000

Kh

Ox

n! NN


20/29

N phu thuoc vao ban chat chat thamgia qua trnh ien cc (N0, n) nhiet oT, nong o chat tham gia qua trnhien cc C.

Ta co:UG = -nFN, hayUG0 = -nFN0

Sau ay la bang the ien cc tieuchuan cua mot so ban phan ng(The Ox-Kh).


21/29

Banphan ng1bar,298K, Ci = 1M

N0 (V)

Li+(aq) + e Li(s) 3.05

K+(aq) + e K(s) 2.93

Ba2+(aq) + 2e Ba(s) 2.91

Ca2+(aq) + 2e Ca(s) 2.76

Na+(aq) + e Na(s) 2.71

Mg2+(aq) + 2e Mg(s) 2.38

Be2+(aq) + 2e Be(s) 1.85

Al3+(aq) + 3e Al(s) 1.68

Ti3+(aq) + 3e Ti(s) 1.21

Mn2+(aq) + 2e Mn(s) 1.18

Sn(s) + 4H+ + 4e SnH4(g) 1.07

2 H2O(l)+2eH

2(g)+2OH(aq) 0.83

Zn2+(aq) + 2e Zn(s) 0.76

Cr3+(aq) + 3e Cr(s) 0.74

Fe2

+(aq) + 2e Fe(s) 0.44

Cr3+(aq) + e Cr2+(aq) 0.42

Sn2+(aq) + 2e Sn(s) 0.13

2H+(aq) + 2e H2(g) 0.00

Sn4+(aq) + 2e Sn2+(aq) +0.15

Cu2+(aq) + e Cu+(aq) +0.16

SO42(aq) + 4H+ + 2e

2H2O(l) + SO

2(aq)

+0.17

Cu2+(aq) + 2e Cu(s) +0.34

O2(g)+2H

2O(l)+4e 4OH(aq) +0.40

SO2(aq)+4H++4eS(s)+ 2H

2O +0.50

Cu+(aq) + e Cu(s) +0.52

I2(s) + 2e 2I(aq) +0.54


22/29

MnO4(aq) + 2H

2O(l) + 3e

MnO2(s) + 4 OH(aq)

+0.59

S2O32

+ 6H+ + 4e 2S(s) +3H

2O

+0.60

O2(g) + 2H+ + 2e H

2O

2(aq) +0.70

Fe3+(aq) + e Fe2+(aq) +0.77

Hg22+(aq) + 2e 2Hg(l) +0.80

Ag+(aq) + e Ag(s) +0.80

NO3(aq) + 2H+(aq) +e

NO2(g) + H

2O(l)

+0.80

Hg2+(aq) + 2e Hg(l) +0.85

MnO

4

(aq) + H+

+ e

HMnO4

(aq)+0.90

2Hg2+(aq) + 2e Hg22+(aq) +0.91

MnO2(s) + 4H+ + e Mn3+(aq)

+ 2H2O

+0.95

Br2(aq) + 2e 2Br(aq) +1.09

2IO3(aq) + 12H+ + 10e I

2(s)

+ 6H2O

+1.20

ClO4(aq) + 2H+ + 2e

ClO3(aq) + H

2O

+1.20

O2(g) + 4H+ + 4e 2H

2O +1.23

MnO2(s) + 4H+ + 2e

Mn2+(aq) + 2H2O

+1.23

Cl2(g) + 2e 2Cl(aq) +1.36

Cr2O7

2(aq) + 14H+ + 6e

2Cr3+(aq) + 7H2O

+1.36

MnO4(aq) + 8H+ + 5e

Mn2+(aq) + 4H2O

+1.51

2HClO(aq) + 2H+ + 2e Cl2(g)+ 2H

2O

+1.63

MnO4(aq) + 4H+ + 3e

MnO2(s) + 2H

2O

+1.70

H2O

2(aq) + 2H+ + 2e 2H

2O +1.76


23/29

The hieu cc ai xuat hien gia haicc ca nguyen to ganvanic goi la scien ong cua nguyen to ganvanic,khi ma nguyen to galvanic hoat ong T

N.

Khieu:

Sc ien ong tieu chuan cuanguyen to galvanic. E0 o p = 1 atm, CM

(hay a) = 1, 298K.

NN!E

000

E NN!


24/29

aKh1 + bOXH2' cOXH1 + dKh2

-(G = A = nFE

b

2

a

1

d

2

c

10

OXHKh

KhOXHlnRTGG (!(

b

2

a

1

d

2

c

1

OXHKh

KhOXH

lnRTKlnRTnFE !

b

2

a

1

d

2

c

1

OXHKh

KhOXHln

nF

RTKln

nF

RTE !

KlnnF

RTE0 !

(G0

= -nFE0

ba

dc

OXHKh

KhOXH

nF

RTEE

21

210ln!

cd

sp

nF

RT

EEln

0!


25/29

Vduviphan ng trongnguyen to

galvanic:Zn + Cu+2 = Zn+2 + Cu

ViN+ lacuacap Cu+2/Cu vaN- la

cuacap Zn+2

/Zn, taco

2

2

ln

2

0

//

!

Cu

Zn

ZnCuZnCu

C

C

F

RTEE

V...EZn/Cu

1176303370000

!!!

NN


26/29

3324FeCeFeCeXet phan ng:

34CeeCe

23FeeFe N

o

=1.700V

No=0.767V

c tao thanh bi 2 ban phan ng sau

V No cua cerium ln hn nen no la chat Oxy hoa.Ta co

(0.767)-1.700-E ooo !!

NN


27/29

Trong nguyen to galvanic co:

]][Ce[Fe

]][Ce[Feln

nF

RT---E

42

3300

-

!! NNNN

Tai can bang, E = 0 va:

1610K}

C25,Klog05916.]][Ce[Fe

]][Ce[Feln

F

RT- o

42

33oo v!!

NN


28/29

Xet caccap O-K: Ox1/Kh1 , Ox2/Kh2

Kh1' Ox1 + ne ,N1

Kh2'

Ox2 + ne ,N2Khi troncaccapnay,se co phanng:

Kh1 + Ox2 ' Ox1 + Kh2

Phan ng xay ra theo chieu thuan khi:

121212

0 NNNN "!!( nFnFEG/


29/29

Quy tac xet chieu phan ng:

Phan ng O K xay ra theo chieudang Ox cua cap O K co N ln hnse Ox dang Kh cua cap O K co N

nho hn.

Thc te co the dung N0 e xet.Nhng khi N0+ - N0- be qua thphai tnh toan tren N.

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Chuong11- Dien Hoa