312 107 Basic Chemistry
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312 107 Basic Chemistry. การถ่ายโอนอิเล็คตรอน. (Electron Transfer). อ.ดร. รจนา บุระคำ. เคมีไฟฟ้า. กระบวนการเปลี่ยนแปลงพลังงานที่เกิดจากปฏิกิริยาเคมี ให้เป็นพลังงานไฟฟ้า และการใช้พลังงานไฟฟ้าทำให้ เกิดการเปลี่ยนแปลงทางเคมี. ปฏิกิริยารีดอกซ์ (ออกซิเดชัน-รีดักชัน).

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312 107 Basic Chemistry

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312 107 basic chemistry

312 107 Basic Chemistry

(Electron Transfer)

..


312 107 basic chemistry

(-)


312 107 basic chemistry

(Redox reaction)

(-)


312 107 basic chemistry

(O.N.)

1. ( O.N. = )

Mg , O2 , O3 , S8 , Cl2 , P4

2. 1 O.N. = 1

LiNO3 , NaCl , KClO3

3. 2 O.N. = 2

MgCl2 , CaCO3 , BeCl2

4. O.N. = 1

HCl , NH3 , H2O

NaH , AlH3 H O.N. = -1


312 107 basic chemistry

(O.N.)

5. O.N. = - 2

H2O , CO2

H2O2 , NaO2 , OF O O.N. -2

6. O.N.

KMnO4 , MnO2 , Na2C2O4

7. O.N.

MnO4- , Cr2O72- , Fe(CN)63-


312 107 basic chemistry

Mn2O7 =2Mn + 7O

2Mn + 7(-2)= 0

2Mn=14

Mn=+7

MnSO4 =Mn + SO4

Mn + (-2)= 0

Mn=+2

C2O42- =2C + 4O

2C + 4(-2)= -2

2C= 6

C= +3


312 107 basic chemistry

2KMnO4 + 5H2S + H2SO4 K2SO4 + MnSO4 + S + H2O

2KMnO4 + 5H2S + 3H2SO4 K2SO4 + 2MnSO4 + 5S + 8H2O

1.

KMnO4 + H2S + H2SO4 K2SO4 + MnSO4 + S + H2O

+2

0

+7

-2

2 5


312 107 basic chemistry

Mn2+ + PbO2 MnO4- + Pb2+

Mn2+ + 4H2O MnO4- + 8H+ + 5e- ()

PbO2 + 4H+ + 2e- Pb2+ + 2H2O ()

2(Mn2+ + 4H2O MnO4- + 8H+ + 5e-)

5(PbO2 + 4H+ + 2e- Pb2+ + 2H2O)

2Mn2+ + 5PbO2 + 4H+ 2MnO4- + 5Pb2+ + 2H2O

2.

.


312 107 basic chemistry

FeCl3 + SnCl2 FeCl2 + SnCl4

KMnO4 + KNO2 + H2SO4 MnSO4 + H2O + KNO3 + K2SO4

Bi(OH)3 + MnO4- BiO3- + MnO2

H+ + NO3- + Cu2O Cu2+ + NO + H2O


312 107 basic chemistry

Ex : (Cu) AgNO3 Cu Cu AgNO3

(Cu) Cu2+

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

()

Ag+ Ag () Cu

Ag+(aq) + e- Ag(s)

()

Cu(s) + Ag+(aq) Cu2+(aq) + 2Ag(s)


312 107 basic chemistry

(Electrode) 2

2

  • (Galvanic cell)

  • (Electrolytic cell)


312 107 basic chemistry

e- (anode) ()

e- (cathode) ()

2


312 107 basic chemistry

Voltmeter

KCl

Zn

anode

Cu

cathode

Zn2+

Cu2+

1.

-

-

-

- 2


312 107 basic chemistry

2.

3. ()

KNO3, KCl, NH4NO3

4.


312 107 basic chemistry

Voltmeter

KCl

Zn

anode

Cu

cathode

Zn2+

Cu2+

Cu2+(aq) + Zn(s) Cu(s) + Zn2+(aq)

Zn(s) Zn2+ + 2e-

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

Zn Cu

e-

e- e-


312 107 basic chemistry

1.

2.

3. | |

A(s) + B+(aq) A+(aq) + B(s)

A(s) | A+(aq) | | B+(aq) | B(s)


312 107 basic chemistry

4.

Cu(s) | Cu2+(aq)(0.1M) | | Ag+(aq)(0.1M) | Ag(s)

5. Pt

: Pt(s) | H2(g) | H+(aq)

: H+(aq) | H2(g) | Pt(s)

6. 1 ,

: Pt(s) | Fe3+(aq) , Fe2+(aq)

: Co3+ (1.0 M), Co2+ (0.1 M) | Pt


312 107 basic chemistry

Fe | Fe2+(aq) || Ni2+(aq) | Ni

Pt | H2 | H+(aq) || Cu2+(1 M) | Cu

Al | Al3+(aq) || Cu2+(aq) | Cu


312 107 basic chemistry

(Standard hydrogen electrode, SHE)

1

Pt

1 mol/l

25C

0.00


312 107 basic chemistry

H2(1 atm) 2H+ + 2e-

2H+ + 2e- H2(1 atm)


312 107 basic chemistry

-

E e- E

()

()

E Ereduction Eoxidation

Ereduction


312 107 basic chemistry

-

Ecell

E

E

Ecell


312 107 basic chemistry

E

()

(1) Ecell = Ecathode - Eanode

E

(2) Ecell = Eox + Ered

E E

(Eox = -Ered)


312 107 basic chemistry

0.34 V

e-

e-

H2(g)

Cu

Cu2+

SO42-

H+

Cl-

1 M CuSO4

1 M HCl

Ecell = Ecathode - Eanode

0.34 = ECu - EH2

ECu = 0.34 0.00 = 0.34


312 107 basic chemistry

. Ecell

Al | Al3+(aq) || Cu2+(aq) | Cu

()

2(Al(s) Al3+(aq) + 3e-) E = -1.66

3(Cu2+(aq) + 2e- Cu(s)) E = +0.34

()

()

2Al(s) + 3Cu2+(aq) 2Al3+(aq) + 3Cu(s) Ecell = ?

Ecell = Ecathode - Eanode

Ecell = 0.34 (-1.66) = 2.00

Ecell = Eox + Ered

= 1.66 + 0.34 = 2.00


312 107 basic chemistry

.

Fe3+(aq) + Cu(s) Fe2+(aq) + Cu2+(aq)

Cu(s) Cu2+(aq) + 2e- E= 0.34

()

2(Fe3+(aq) + e- Fe2+(aq)) E = 0.77

()

Cu(s) + 2Fe3+ Cu2+(aq) + 2Fe2+(aq) E = ?

()

Ecell = Ecathode - Eanode

= 0.77 0.34 = 0.43


312 107 basic chemistry

Ecell G K

G = - nFEcell

G = - 2.303 RT log K

G

log K = -

2.303 RT

nFEcell

log K =

2.303 RT

nEcell

Log K =

0.0592


312 107 basic chemistry

Ecell G K

G

K

Ecell

1

1

1

+

0

-

-

0

+


312 107 basic chemistry

. G

Cu2+(aq) + Fe(s) Cu(s) + Fe2+(aq)

Ecell

Fe Fe2+ + 2e- E = 0.44

Cu2+ + 2e- Cu E = 0.34

Cu2+ + Fe Cu + Fe2+ Ecell = 0.78

G

G = -nFEcell

= - 2 x 96500 x 0.78 J

= - 1.5 x 105 J

Ecell G


312 107 basic chemistry

0.0592

E = E -

log Q

n

1 M

1 M

E

E =

E =

n =

Q =


312 107 basic chemistry

Ecell


312 107 basic chemistry

. Ecell 2Al(s) + 3I2(s) 2Al3+(aq) + 6I-(aq)

Al Al3+ 0.10 M

I2 I- 0.01 M Ecell = 2.20

n ()

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

()

I2 + 2e- 2I-

()

( 2 3)

2(Al(s) Al3+(aq) + 3e-)

3(I2(s) + 2e- 2I-(aq)

n = 6


312 107 basic chemistry

0.0592

Ecell= Ecell -

log Q

n

Ecell

0.0592

= 2.20 -

log [Al3+]2 [I-]6

6

log (0.1)2 (0.01)6

0.0099

= 2.20 -

= 2.34


312 107 basic chemistry

Ecell Ecell


312 107 basic chemistry

0.0592

Ecell= Ecell -

log Q

n

. HCl -

Pt | H2 | H+(aq) || Cu2+(1 M) | Cu

Ecell Ecell 0.34 0.30

H2(g) + Cu2+(aq) Cu(s) + 2H+(aq)

[HCl]

0.30 = 0.34 -

[H+]

0.0592

log

6

1

[H+] = [HCl] = 4.74 M


312 107 basic chemistry

(Keq)

(Ksp)

Ecell


312 107 basic chemistry

0.0592

Ecell= Ecell -

log Q

n

Ecell = 0 Q = K

0.0592

0= Ecell -

log K

n

nEcell

log K =

0.0592


312 107 basic chemistry

.

MnO4- + Br- + H+ Mn2+ + Br2 + H2O

Ecell

5(2Br- Br2 + 2e-) E = -1.09

2(MnO4- + 8H+ + 5e- Mn2+ + 4H2O) E = 1.51

2MnO4- + 10Br- + 16H+ 2Mn2+ + 5Br2 Ecell = 0.42

nEcell

K

= 10 x 0.42

= 70.95

log K =

0.0592

0.0592

K = 8.83 x 1070


312 107 basic chemistry

. Ksp AgCl

AgCl(s) Ag+(aq) + Cl-(aq)

Ecell

AgCl(s) + e- Ag(s) + Cl-(aq) E = 0.22

Ag+(aq) + e- Ag(s) E = 0.80

Ecell = - 0.58

nEcell

= (1) (-0.58)

Ksp

log Ksp =

= - 9.8

0.0592

0.0592

Ksp = 6.27 x 10-10


312 107 basic chemistry

C1

0.0592

Ecell= Ecell -

log

n

C2

(concentration cell)

C1 C2 (C2C1)

Ecell = 0


312 107 basic chemistry

. Ecell

Ag | Ag+(0.01 M) || Ag+(0.1 M) | Ag

Ecell

C1

0.0592

Ecell= Ecell -

log

n

C2

0.01

0.0592

log

= 0 -

1

0.1

= 0.0592


312 107 basic chemistry

- (primary galvanic cell)


312 107 basic chemistry

Zn Zn2+ + 2e-

MnO2

2e- + 2MnO2 + 2NH4+ Mn2O3 + H2O + 2NH3

Zn2+ NH3

Zn2+ + 4NH3 [Zn(NH3)4]2+

1.5

NH4+ MnO2 H2

2NH4+ + 2e- 2NH3 + H2

H2 MnO2 H2 H2O

MnO2 + H2 MnO + H2O


312 107 basic chemistry

(fuel cell)

-

()

2(H2(g) + 2OH-(aq) 2H2O + 2e-)

()

O2(g) + 2H2O + 4e- 4OH-(aq)

()

2H2(g) + O2(g) 2H2O


312 107 basic chemistry

- (secondary galvanic cell)

Pb(s) + SO42-(aq) PbSO4(s) + 2e-

()

()

PbO2(s) + 2e- + SO42-(aq) + 4H+(aq) PbSO4(s) + 2H2O

()

Pb(s) + PbO2(s) + 4H+(aq) + 2SO42-(aq) 2PbSO4(s) + 2H2O


312 107 basic chemistry

SO42- H+

PbSO4

Pb PbO2

2PbSO4 + 2H2O Pb + PbO2 + 4H+ + 2SO42-


312 107 basic chemistry

Li (s) ------> Li+(s) + e- TiS2(s) + e- -----> TiS2 -(s) Li(s) + TiS2(s) -----> Li+(s) + TiS2-(s)

(TiS2)


312 107 basic chemistry


312 107 basic chemistry

(Electrolytic cell)

1. 2


312 107 basic chemistry

2.

3.


312 107 basic chemistry

(Electrolysis)

-

()

()


312 107 basic chemistry

2Cl- Cl2(g) + 2e- E = 1.36

()

2(Na+ + e- Na(s) E = -2.71

()

2Cl- + 2Na+ Cl2(g) + 2Na(s) Ecell = -4.07

()

Ecell

4.07


312 107 basic chemistry

Q = It

Q = ()

I = ()

t = ()


312 107 basic chemistry

  • 2.


312 107 basic chemistry

. 12 CuSO4

2 (Cu = 63.54)

Q = It

= 12 x 2 x 60 x 60

= 86400

96500 1

86400 = 0.8953

86400

96500

Cu2+

Cu2+ + 2e- Cu

2 63.54

0.8953 = 28.44

63.54 x 0.8956

2


312 107 basic chemistry

1. Al Al2O3

() 3O2- 3O2(g) + 6e-

2

() 2(Al3+ + 3e- Al(l))

2Al3+ + 3O2- 2Al(l) + 3 O2(g)

2


312 107 basic chemistry

2.

()

Cu(s) Cu2+ + 2e-

()

Cu2+ + 2e- Cu(s)


312 107 basic chemistry

3.

Ag+

()

Ag(s) Ag+ + e-

()

Ag+ + e- Ag(s)


312 107 basic chemistry

(corrosion)

( )


312 107 basic chemistry

(Fe(s)) Fe2+

Fe(s) Fe2+ + 2e-

O2(g) + H2O(g) + 2e- 2OH-

Fe(s) + O2(g) + H2O(g) Fe2+ + 2OH-


312 107 basic chemistry

Fe2+ OH-

Fe(OH)2

Fe(OH)3

2Fe(OH)2 + O2 + H2O 2Fe(OH)3 Fe2O33H2O


312 107 basic chemistry

1.

2. (

)


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