Electrolysis

Electrolysis describes what happens in an electrolytic cell andmeans to use electricity to make chemicals.

Pb Al Zn Na K Li H2 Cl2 F2

I2 O2 are all made by electrolysis

When metals are made by electrolysis it is sometimes called electrowinning as the metal is won from the ion as it is reduced.

Pb2+ + 2e- → Pb(s)

2Cl- → Cl2(g) + 2e-

Electrolysis of Aluminum Alcan Kitimat B.C.

Name of the Ore used: Bauxite Al2O3

.3H2O

Heating drives off the water

Al2O3.3H2O + Heat → Al2O3 + 3H2O

 Melting point of Bauxite is 2045 0C

This is too hot!Cryolite is added Lowers the melting point to 1000 0C

DC Power - +

Al2O3(l)

CC

DC Power - +

Al2O3(l)

CC

Al3+

O2-

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

reduction

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

+

Oxidation

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

+

Oxidation

Anode

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

+

Oxidation

Anode

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

Al3+ + 3e- → Al(s)

+

Oxidation

Anode

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

Al3+ + 3e- → Al(s)

+

Oxidation

Anode

2O2- → O2 + 4e-

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

Al3+ + 3e- → Al(s)

+

Oxidation

Anode

2O2- → O2 + 4e-

Liquid Al floats to the top and is removed.

DC Power - +

Al2O3(l)

CC

Al3+

O2-

-

Reduction

Cathode

Al3+ + 3e- → Al(s)

+

Oxidation

Anode

2O2- → O2 + 4e-

Liquid Al floats to the top and is removed.

Oxygen gas

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.

K2SO4(aq)

DC Power

- +

CuCu

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced.

K2SO4(aq)

DC Power

- +

CuCu

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced.

DC Power

- +

K2SO4(aq)

CuCu

2K+

SO42-

H2O

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced.

DC Power

- +

K2SO4(aq)

CuCu

2K+

SO42-

H2O

-

Cathode

Reduction

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced.

DC Power

- +

K2SO4(aq)

CuCu

-

Cathode

Reduction

2H2O + 2e-→H2 +2OH-

-0.41 v

2K+

SO42-

H2O

Non-Inert ElectrodesYou must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced.

DC Power

- +

K2SO4(aq)

CuCu

-

Cathode

Reduction

2H2O + 2e-→H2 +2OH-

-0.41 v

+

Anode

Oxidation

2K+

SO42-

H2O

You must look at the possible oxidation of:

H2O SO4

2- CuCheck out the reduction chart!

S2O82- + 2e- → 2SO4

2- 2.01 v

1/2O2 + 2H+(10-7M) → H20 0.82 v

Cu+ + 1e- → Cu(s) 0.52 v

Cu2+ + 2e- → Cu(s)* 0.34 v* Strongest Reducing Agent

Non-Inert Electrodes

You must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced. 

DC Power

- +

K2SO4(aq)

CuCu

2K+

SO42-

-

Cathode

Reduction

2H2O + 2e-→H2 +2OH-

-0.41 v

+

Anode

Oxidation

Cu(s) → Cu2++2e-

-0.34 v

Non-Inert Electrodes

You must understand that a non-inert Anode might oxidize.The Cathode will stay inert because it already is reduced. 

DC Power

- +

K2SO4(aq)

CuCu

2K+

SO42-

-

Cathode

Reduction

2H2O +2e→H2(g)+2OH-

-0.41 v

+

Anode

Oxidation

Cu(s) → Cu2++2e-

-0.34 v

2H2O + Cu(s) → Cu2++ H2 +2OH- E0 = -0.75 v MTV = +0.75 v

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

Pourous membrane

Or it might look like this

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Is this cell electrolytic or electrochemical?

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Electrochemical- There is no power supplyCu is higher and the cathodeZn is lower and the anode.

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Electrochemical- Cu is higher and the cathodeZn is lower and the anode.

CathodeReductionNo Cu2+ to reduce!

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Electrochemical- Cu is higher and the cathodeZn is lower and the anode.

CathodeReduction2H+ + 2e- → H2(g)

0.00 v

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Electrochemical- Cu is higher and the cathodeZn is lower and the anode.

CathodeReduction2H+ + 2e- → H2(g)

0.00 v

AnodeOxidationWhat oxidizes?ZnH2OCl-

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

Electrochemical- Cu is higher and the cathodeZn is lower and the anode.

CathodeReduction2H+ + 2e- → H2(g)

0.00 v

AnodeOxidationZn → Zn2+ + 2e-

0.76 v

HCl(aq)

ZnCu

0.76 v Voltmeter

Analyze This Cell

H+

H2O

Cl-

2H+ + Zn(s) → Zn2+ + H2(g) E0 = 0.76 v

CathodeReduction2H+ + 2e- → H2(g)

0.00 v

AnodeOxidationZn(s) → Zn2+ + 2e-

0.76 v

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Cathode: Electrolyte:

DC Power

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Electrolyte:

DC Power

Ni

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte:

DC Power

Cu

Ni

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte: Ni(NO3)2

DC Power

Cu

Ni

Ni2+

NO3-

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte: Ni(NO3)2

DC Power- +

Cu

Ni

Ni2+

NO3-

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte: Ni(NO3)2

DC Power- +

Cu

Ni

Ni2+

NO3-

-ReductionCathode

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal  Must be negative!Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte: Ni(NO3)2

DC Power- +

Cu

Ni

Ni2+

NO3-

-ReductionCathodeNi2+ + 2e- → Ni(s)

Electroplating 

Electroplating is the process of reducing a metal on to the surface of another. Anode: Metal to be plated on top the other metal Cathode: The other metal to be covered with the new metal Electrolyte: Must contain the ion of the metal that plates Ni plating a Cu penny Anode: Ni Cathode: Cu Electrolyte: Ni(NO3)2

DC Power- +

Cu

Ni

Ni2+

NO3-

-ReductionCathodeNi2+ + 2e- → Ni(s)

+OxidationAnodeNi(s) → Ni2+ + 2e-

e-

Silver plating a Loonie Anode: Cathode:

Electrolyte:  

DC Power

$1

Silver plating a Loonie Anode: Ag Cathode:

Electrolyte:  

DC Power

$1

Ag

Silver plating a Loonie Anode: Ag Cathode: Loonie

Electrolyte:  

DC Power- +

$1

Ag

Loonie

Silver plating a Loonie Anode: Ag Cathode: Loonie

Electrolyte: AgNO3

 

DC Power- +

$1

Ag

Loonie

Ag+

NO3-

Silver plating a Loonie Anode: Ag Cathode: Loonie

Electrolyte: AgNO3

 

DC Power- +

$1

Ag

Loonie

Ag+

NO3-

-ReductionCathodeAg+ + 1e- → Ag(s)

+OxidationAnodeAg(s) → Ag+ + 1e-

e- e-

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Anode:

Electrolyte:

DC Power- +

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Pure Pb Anode:

Electrolyte:

DC Power- +

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Pure Pb Anode: Impure Pb

Electrolyte:

DC Power- +

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Pure Pb Anode: Impure Pb

Electrolyte: Pb(NO3)2

DC Power- +

Pb2+

NO3-

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Pure Pb Anode: Impure Pb

Electrolyte: Pb(NO3)2

DC Power- +

Pb2+

NO3-

-ReductionCathode

Pb2+ + 2e- → Pb(s)

Electrorefining Electrorefining is the process of purifying a metal by electrolysis.Impure metal is oxidized at the anode and pure metal is reduced at the cathode.This is the same as electroplating. The Electrorefinning of Lead Cominco Trail, B.C. 

 Cathode: Pure Pb Anode: Impure Pb

Electrolyte: Pb(NO3)2

DC Power- +

Zn2+

Pb2+

NO3-

-ReductionCathode

Pb2+ + 2e- → Pb(s)

+OxidationAnode

Pb(s) → Pb2+ + 2e- Au Cu