ELECTROLYSIS
A guide for GCSE students
2010
KNOCKHARDY PUBLISHING SPECIFICATIONS
ELECTROLYSIS
INTRODUCTION
This Powerpoint show is one of several produced to help students understand selected GCSE Chemistry topics. It is based on the requirements of the AQA specification but is suitable for other examination boards. Individual students may use the material at home for revision purposes and it can also prove useful for classroom teaching with an interactive white board. Accompanying notes on this, and the full range of AS and A2 Chemistry topics, are available from the KNOCKHARDY WEBSITE at...
www.knockhardy.org.uk
All diagrams, photographs and any animations in this Powerpoint are original and created by Jonathan Hopton. Permission must be obtained for their use in any work that is distributed for financial gain.
ELECTROLYSIS
CONTENTS
What is electrolysis? Electrolysis of ionic compounds Electrolysis of molten sodium chloride Electrolysis of aqueous sodium chloride (brine)
Diaphragm cell
Electrolysis of aluminium oxide Other electrolytic systems Electrolysis of water
ELECTROLYSIS
Passing an electric current through ionic substances that are molten or in aqueous solution, breaks them down into elements.
ELECTROLYSIS
Passing an electric current through ionic substances that are molten or in aqueous solution, breaks them down into elements. The process is known as
ELECTROLYSIS
ELECTROLYSIS
Passing an electric current through ionic substances that are molten or in aqueous solution, breaks them down into elements. The process is known as
ELECTROLYSIS ELECTROLYTE
The substance broken down is called the
ELECTROLYSIS
Passing an electric current through ionic substances that are molten or in aqueous solution, breaks them down into elements. The process is known as
ELECTROLYSIS ELECTROLYTE
The substance broken down is called the
During electrolysis
Positively charged ions move to the negative electrode - CATHODE Negatively charged ions move to the positive electrode - ANODE
ELECTROLYSIS
Passing an electric current through ionic substances that are molten or in aqueous solution, breaks them down into elements. The process is known as
ELECTROLYSIS ELECTROLYTE
The substance broken down is called the
During electrolysis
Positively charged ions move to the negative electrode - CATHODE Negatively charged ions move to the positive electrode - ANODE
CATHODE ANODE
+ive ions gain electrons - ive ions give up (lose) electrons
REDUCTION OXIDATION
ELECTROLYSIS OF IONIC COMPOUNDS
CONDUCTING ELECTRICITY
CONDUCTING ELECTRICITY
For a substance to conduct electricity it must have either
CONDUCTING ELECTRICITY
For a substance to conduct electricity it must have either electrons which are free to move about (metals / graphite)
CONDUCTING ELECTRICITY
For a substance to conduct electricity it must have either electrons which are free to move about or ions which are free to move about (metals / graphite)
CONDUCTING ELECTRICITY
For a substance to conduct electricity it must have either electrons which are free to move about or ions which are free to move about (metals / graphite)
When an ionic substance is melted or dissolved in water, the ions are free to move about within the liquid or solution.
ELECTROLYSIS OF IONIC COMPOUNDS
SOLID
ClNa+
Na+
ClNa+
Na+
ClNa+
ClNa+
Cl-
Cl-
WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY
SOLID IONIC COMPOUNDS DONT CONDUCT ELECTRICITY
ELECTROLYSIS OF IONIC COMPOUNDS
SOLID MOLTEN
Na+ Na+
ClNa+
Na+
ClNa+
ClNa+
ClNa+
ClNa+
ClNa+
ClNa+
Cl-
Cl-
Cl-
WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY
WHEN MOLTEN, THE IONS ARE FREE TO MOVE ELECTRICITY IS CONDUCTED
MOLTEN IONIC COMPOUNDS DO CONDUCT ELECTRICITY
ELECTROLYSIS OF IONIC COMPOUNDS
SOLID
ClNa+
Na+
ClNa+
Na+
ClNa+
ClNa+
Cl-
Cl-
WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY
SOLID IONIC COMPOUNDS DONT CONDUCT ELECTRICITY
ELECTROLYSIS OF IONIC COMPOUNDS
SOLID
ClNa+
Na+
ClNa+
Na+
ClNa+
ClAdd to water
Na+
Cl-
Cl-
WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY
AQUEOUS SOLUTIONS OF IONIC COMPOUNDS DO CONDUCT ELECTRICITY
ELECTROLYSIS OF IONIC COMPOUNDS
SOLID IN AQUEOUS SOLUTION
Na+ Na+
ClNa+
Na+
ClNa+
ClNa+
ClNa+
ClNa+
ClNa+
ClNa+
Cl-
Cl-
Cl-
WHEN SOLID, THE IONS ARE NOT FREE TO MOVE NO CONDUCTION OF ELECTRICITY
WHEN DISSOLVED IN WATER, THE IONS ARE FREE TO MOVE ELECTRICITY IS CONDUCTED
AQUEOUS SOLUTIONS OF IONIC COMPOUNDS DO CONDUCT ELECTRICITY
ELECTROLYSIS OF MOLTEN SODIUM CHLORIDE
ELECTROLYSIS OF SODIUM CHLORIDE DOWNS CELL
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE SODIUM IONS GO TO THE CATHODE AND EACH PICK UP AN ELECTRON Na+ + eNa
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE SODIUM IONS GO TO THE CATHODE AND EACH PICK UP AN ELECTRON Na+ + eNa
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE SODIUM IONS GO TO THE CATHODE AND EACH PICK UP AN ELECTRON Na+ + eNa
CHLORIDE IONS GO TO THE ANODE AND EACH GIVE UP AN ELECTRON
Cl2ClCl + eCl2 + 2e-
ELECTROLYSIS OF SODIUM CHLORIDE
SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE SODIUM IONS GO TO THE CATHODE AND EACH PICK UP AN ELECTRON Na+ + eNa
CHLORIDE IONS GO TO THE ANODE AND EACH GIVE UP AN ELECTRON
Cl2ClCl + eCl2 + 2e-
ELECTROLYSIS OF SODIUM CHLORIDE
SUMMARY SOLID SODIUM CHLORIDE DOES NOT CONDUCT ELECTRICITY BECAUSE THE IONS ARE NOT FREE TO MOVE TO THE ELECTRODES WHEN MOLTEN, THE IONS HAVE MORE FREEDOM AND CAN MOVE SODIUM IONS GO TO THE CATHODE AND EACH PICK UP AN ELECTRON Na+ + eNa
CHLORIDE IONS GO TO THE ANODE AND EACH GIVE UP AN ELECTRON
Cl2ClCl + eCl2 + 2e-
ELECTROLYSIS OF AQUEOUS SODIUM CHLORIDE (BRINE)
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE WATER CONTAINS A FEW IONS
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE WATER CONTAINS A FEW IONS POSITIVE IONS ARE ATTRACTED TO THE NEGATIVE CATHODE...
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE WATER CONTAINS A FEW IONS POSITIVE IONS ARE ATTRACTED TO THE NEGATIVE CATHODE... OF THE TWO, HYDROGEN IONS ARE PREFERRED
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE WATER CONTAINS A FEW IONS POSITIVE IONS ARE ATTRACTED TO THE NEGATIVE CATHODE... OF THE TWO, HYDROGEN IONS ARE PREFERRED NEGATIVE IONS ARE ATTRACTED TO THE POSITIVE ANODE...
ELECTROLYSIS OF BRINE
WHEN SODIUM CHLORIDE DISSOLVES IN WATER, THE IONS SEPARATE WATER CONTAINS A FEW IONS POSITIVE IONS ARE ATTRACTED TO THE NEGATIVE CATHODE... OF THE TWO, HYDROGEN IONS ARE PREFERRED NEGATIVE IONS ARE ATTRACTED TO THE POSITIVE ANODE... OF THE TWO, CHLORIDE IONS ARE PREFERRED
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + eH
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
The atoms form molecules and hydrogen gas H2 is produced
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
AT THE POSITIVE ANODE CHLORIDE IONS GIVE UP AN ELECTRON AND BECOME ATOMS ClCl + e-
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
AT THE POSITIVE ANODE CHLORIDE IONS GIVE UP AN ELECTRON AND BECOME ATOMS Cl2ClCl + eCl2 + 2e-
The atoms form molecules and chlorine gas Cl2 is produced
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
AT THE POSITIVE ANODE CHLORIDE IONS GIVE UP AN ELECTRON AND BECOME ATOMS Cl2ClCl + eCl2 + 2eSODIUM HYDROXIDE SOLUTION REMAINS
ELECTROLYSIS OF BRINE
AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
AT THE POSITIVE ANODE CHLORIDE IONS GIVE UP AN ELECTRON AND BECOME ATOMS Cl2ClCl + eCl2 + 2eSODIUM HYDROXIDE SOLUTION REMAINS
ELECTROLYSIS OF BRINE
SUMMARY AT THE NEGATIVE CATHODE HYDROGEN IONS PICK UP AN ELECTRON AND BECOME ATOMS H+ + e2H+ + 2eH H2
AT THE POSITIVE ANODE CHLORIDE IONS GIVE UP AN ELECTRON AND BECOME ATOMS Cl2ClCl + eCl2 + 2eSODIUM HYDROXIDE SOLUTION REMAINS
INDUSTRIAL ELECTROLYSIS OF BRINE
SODIUM CHLORIDE THE DIAPHRAGM CELL
CHLORINE GAS HYDROGEN GAS
BRINE
IONS
IONS
DIAPHRAGM
STOPS CHLORINE MIXING WITH SODIUM HYDROXIDE
SODIUM HYDROXIDE SOLUTION
(CAUSTIC SODA)
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS AN ADVANTAGE OF ELECTROLYSING BRINE RATHER THAN MOLTEN SODIUM CHLORIDE?
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS AN ADVANTAGE OF ELECTROLYSING BRINE RATHER THAN MOLTEN SODIUM CHLORIDE?
LESS ENERGY IS NEEDED BECAUSE YOU DONT HAVE TO MELT THE SODIUM CHLORIDE; IT HAS A HIGH MELTING POINT
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT HAPPENS AT THE POSITIVE ANODE?
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT HAPPENS AT THE POSITIVE ANODE?
CHLORIDE IONS ARE OXIDISED
Cl e 2Cl 2e
Cl Cl2
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT HAPPENS AT THE NEGATIVE CATHODE?
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT HAPPENS AT THE NEGATIVE CATHODE?
HYDROGEN IONS ARE REDUCED
H+ + e 2H+ + 2e
H H2
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS THE DIAPHRAGM FOR?
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS THE DIAPHRAGM FOR?
PREVENTS CHLORINE COMING INTO CONTACT WITH ANY SODIUM HYDROXIDE
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS ALSO PRODUCED?
THE DIAPHRAGM CELL
IMPORTANT ASPECTS
CHLORINE HYDROGEN
BRINE
IONS
IONS
SODIUM HYDROXIDE
(CAUSTIC SODA)
DIAPHRAGM
WHAT IS ALSO PRODUCED?
THE SOLUTION CONTAINS SODIUM IONS AND HYDROXIDE IONS SO SODIUM HYDROXIDE IS PRODUCED
THE DIAPHRAGM CELL
INDUSTRIAL IMPORTANCE
The products of the electrolysis of brine are of great industrial importance
CHLORINE
making bleach making plastics such as pvc used as fuel used in margarine production production of soaps and detergents used in the paper industry
HYDROGEN
SODIUM HYDROXIDE
EXTRACTION OF ALUMINIUM BY ELECTROLYSIS
EXTRACTION OF ALUMINIUM
ELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon. (Aluminium is above carbon in the reactivity series)
EXTRACTION OF ALUMINIUM
ELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon. (Aluminium is above carbon in the reactivity series) Reactive metals are extracted using electrolysis
EXTRACTION OF ALUMINIUM
ELECTROLYSIS
Unlike iron, aluminium cannot be extracted using carbon. (Aluminium is above carbon in the reactivity series) Reactive metals are extracted using electrolysis Electrolysis is expensive - it requires a lot of energy - ore must be molten (ores have high melting points) - electricity is needed for the electrolysis process
EXTRACTION OF ALUMINIUM
RAW MATERIALS
BAUXITE aluminium ore
Bauxite contains alumina (Al2O3 aluminium oxide) plus impurities such as iron oxide it is purified before use.
EXTRACTION OF ALUMINIUM
RAW MATERIALS
BAUXITE aluminium ore
Bauxite contains alumina (Al2O3 aluminium oxide) plus impurities such as iron oxide it is purified before use.
CRYOLITE
Aluminium oxide has a very high melting point. Adding cryolite lowers the melting point and saves energy.
EXTRACTION OF ALUMINIUM
EXTRACTION OF ALUMINIUM
THE CELL CONSISTS OF A
EXTRACTION OF ALUMINIUM
CARBON ANODE
THE CELL CONSISTS OF A
CARBON ANODE
EXTRACTION OF ALUMINIUM
STEEL CATHODE CARBON LINING
THE CELL CONSISTS OF A
CARBON LINED STEEL CATHODE
EXTRACTION OF ALUMINIUM
MOLTEN ALUMINA and CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na3AlF6 SAVES ENERGY - the mixture melts at a lower temperature
EXTRACTION OF ALUMINIUM
MOLTEN ALUMINA and CRYOLITE
ALUMINA IS DISSOLVED IN MOLTEN CRYOLITE Na3AlF6 aluminium and oxide ions are now free to move
EXTRACTION OF ALUMINIUM
POSITIVE ALUMINIUM IONS ARE ATTRACTED TO THE NEGATIVE CATHODE
CARBON CATHODE
Al3+ + 3e-
Al
EACH ION PICKS UP 3 ELECTRONS AND IS DISCHARGED
EXTRACTION OF ALUMINIUM
NEGATIVE OXIDE IONS ARE ATTRACTED TO THE POSITIVE ANODE
CARBON ANODE
O2-
O + 2e-
EACH ION GIVES UP 2 ELECTRONS AND IS DISCHARGED
EXTRACTION OF ALUMINIUM
ELECTRONS
CARBON ANODE
CARBON CATHODE
EXTRACTION OF ALUMINIUM
ELECTRONS OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE CARBON ANODE
ANODE
3O2-
1O2 + 6e-
OXIDATION
EXTRACTION OF ALUMINIUM
ELECTRONS
OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE
REDUCTION (GAIN OF ELECTRONS) TAKES PLACE AT THE CATHODE
CARBON CATHODE
ANODE
CATHODE
3O22Al3+ + 6e-
1O2 + 6e2Al
OXIDATION
REDUCTION
EXTRACTION OF ALUMINIUM
ELECTRONS OXIDATION (LOSS OF ELECTRONS) TAKES PLACE AT THE ANODE CARBON ANODE
REDUCTION (GAIN OF ELECTRONS) TAKES PLACE AT THE CATHODE
CARBON CATHODE
ANODE
CATHODE
3O22Al3+ + 6e-
1O2 + 6e2Al
OXIDATION
REDUCTION
EXTRACTION OF ALUMINIUM
CARBON DIOXIDE
PROBLEM
THE CARBON ANODES REACT WITH THE OXYGEN TO PRODUCE CARBON DIOXIDE
CARBON ANODE
EXTRACTION OF ALUMINIUM
CARBON DIOXIDE
PROBLEM
THE CARBON ANODES REACT WITH THE OXYGEN TO PRODUCE CARBON DIOXIDE
CARBON ANODE
THE ANODES HAVE TO BE REPLACED AT REGULAR INTERVALS, THUS ADDING TO THE COST OF THE EXTRACTION PROCESS
USES OF ALUMINIUM
THE IMPORTANCE OF ALUMINIUM
LOW DENSITY AND ELECTRICAL CONDUCTIVITY
LOW DENSITY needs to be an alloyed with other metals for extra strength GOOD HEAT CONDUCTIVITY
OVERHEAD CABLES
AIRCRAFT BODIES
SAUCEPANS
USES OF ALUMINIUM
THE IMPORTANCE OF ALUMINIUM
LOW DENSITY AND ELECTRICAL CONDUCTIVITY
LOW DENSITY needs to be an alloyed with other metals for extra strength GOOD HEAT CONDUCTIVITY
OVERHEAD CABLES
AIRCRAFT BODIES
SAUCEPANS
Aluminium is not as reactive as one would predict from its position in the reactivity series.
THIN LAYER OF OXIDE
This is because a thin layer of oxide quickly forms on the surface and prevents any further reaction taking place.
USES OF ALUMINIUM
THE IMPORTANCE OF ALUMINIUM
LOW DENSITY AND ELECTRICAL CONDUCTIVITY
LOW DENSITY needs to be an alloyed with other metals for extra strength GOOD HEAT CONDUCTIVITY
OVERHEAD CABLES
AIRCRAFT BODIES
SAUCEPANS
Aluminium is not as reactive as one would predict from its position in the reactivity series.
THIN LAYER OF OXIDE
This is because a thin layer of oxide quickly forms on the surface and prevents any further reaction taking place.
ANODISING puts on a controlled layer of oxide so the metal can be used for household items such as pans and electrical goods.
USES OF ALUMINIUM
ANODISING
This puts on a controlled layer of oxide so that the metal can be used for household items such as pans and electrical goods. The aluminium object is made the anode in the electrolysis of dilute sulphuric acid.
Oxygen given of at the anode reacts with the aluminium surface, to build up a very thin film of oxide. aluminium object to be anodised
cathode
dilute sulphuric acid
ELECTROLYSIS OF
MOLTEN LEAD BROMIDE
ELECTROLYSIS OF
MOLTEN LEAD BROMIDE
Pb2+
Br-
Br-
ANODE CATHODE
ELECTROLYSIS OF
MOLTEN LEAD BROMIDE
Pb Pb2+
Br-
Br
Br
Br-
ANODE CATHODE
2BrPb2+ + 2e-
Br2 + 2ePb
OXIDATION REDUCTION
ELECTROLYSIS OF
DILUTE SULPHURIC ACID
ELECTROLYSIS OF
DILUTE SULPHURIC ACID
SO42-
ANODE CATHODE
ELECTROLYSIS OF
DILUTE SULPHURIC ACID
H H H H
O O SO42-
ANODE CATHODE
4OH4H+ + 4e-
2H2O + O2 + 4e2H2
OXIDATION REDUCTION
ELECTROLYSIS OF
DILUTE SULPHURIC ACID
H H H H
O O SO42-
ANODE CATHODE
4OH4H+ + 4e-
2H2O + O2 + 2H2
4e-
This electrolysis OXIDATION can be used to deduce the REDUCTION formula of water
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with carbon electrodes)
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with carbon electrodes)
SO42Cu2+
ANODE CATHODE
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with carbon electrodes)
O O
Cu
SO42Cu2+
ANODE CATHODE
4OH2Cu2+ + 4e-
2H2O + O2 + 4e2Cu
OXIDATION REDUCTION
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with copper anode)
A different reaction takes place if the anode is made of copper
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with copper anode)
SO42Cu2+
Cu
ANODE CATHODE
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with copper anode)
Cu
SO42Cu2+
Cu
ANODE CATHODE
Cu Cu2+ + 2e-
Cu2+ + 2eCu
OXIDATION REDUCTION
ELECTROLYSIS OF
AQUEOUS COPPER SULPHATE (with copper anode)
Cu
SO42Cu2+
Cu
ANODE CATHODE
Cu Cu2+ + 2e-
Cu2+ + 2eCu
This electrolysis can be used to OXIDATION purify copper or copper plate REDUCTION objects
ELECTROLYSIS OF
DILUTE HYDROCHLORIC ACID
ELECTROLYSIS OF
DILUTE HYDROCHLORIC ACID
Cl-
ANODE CATHODE
ELECTROLYSIS OF
DILUTE HYDROCHLORIC ACID
H H
Cl Cl-
Cl
ANODE CATHODE
2Cl2H+ + 2e-
Cl2 + 2eH2
OXIDATION REDUCTION
COMPOSITION OF WATER
WATER IS AN EXTREMELY POOR CONDUCTOR OF ELECTRICITY. Dilute sulphuric acid must be added to improve Its conductivity.
HOFFMAN VOLTAMETER
Fill both limbs of a Hoffman Voltameter with water, (acidified with a small amount of dilute sulphuric acid). Pass a direct current through the apparatus.
ANODE (+) - a colourless gas collected - the gas re-lit a glowing splint - a colourless gas collected - its volume was twice that at anode - gas exploded with a squeaky pop when a lighted splint was applied Water can be split into its elements by passing electricity through it. water > hydrogen (2 vols) + oxygen (1 vol).
CATHODE (-)
Conclusion
ELECTROLYSIS
THE END
2011 JONATHAN HOPTON & KNOCKHARDY PUBLISHING
