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Redox Chemistry and
Electrolysis.
1
6 consecutive CCEA GCSE Chemistry papers: 2002-7
2002, Paper 1
3
a)
Electrolysis plays an important part
in extracting some metals from their
ores and in purifying others.
Define what is meant by the term
electrolysis.
_________________________________
______________________________ [2]
b) Name one metal which is obtained
from its ore by electrolysis.
______________________________ [1]
3
Electrolysis plays an important part in extracting
some metals from their ores and in purifying
others.
a)
Define what is meant by the term electrolysis.
Electrolysis is decomposition [1] of a substance
using an electric current [1]
Name one metal which is obtained from its ore
by electrolysis.
Any reactive metal at the top of the reactivity
series. Specification refers to aluminium [1]; but
could accept sodium, potassium, calcium,
magnesium, zinc.
b)
c)
Draw a labelled diagram of simple
laboratory apparatus which shows
how copper can be purified.
c)
Draw a labelled diagram of simple laboratory apparatus which
shows how copper can be purified.
Complete circuit (1)
(1)
(1)
(1)
(1)
Electrolyte (1)
Accept any soluble copper salt
d) Write balanced, ionic equations to
show the electrode reactions which
occur when copper is purified.
(i) At the anode ________________ [2]
(ii) At the cathode ______________ [2]
d)
Write balanced, ionic equations to
show the electrode reactions which
occur when copper is purified.
(i)
At the anode Cu → Cu2+ + 2e-
(ii) At the cathode Cu2+ + 2e- → Cu
[2]
[2]
e)
Which particles are responsible for
the conductivity of electricity in:
(i) metals? ____________________ [1]
(ii) electrolytes? ________________ [1]
e)
Which particles are responsible for
the conductivity of electricity in:
(i) metals? Electrons
[1]
(ii) electrolytes? Ions
[1]
f)
Give two uses of copper metal apart
from its use in electrical wiring.
_____________________________
___________________________ [2]
f) Give two uses of copper metal apart
from its use in electrical wiring.
Specification lists:
Plumbing
Brass
Any two for [1] each
Coinage
[2]
g)
The electrolysis of dilute sulphuric
acid using inert electrodes produces
two gases as products.
(i) Name a material which could be used
as the electrodes in this experiment.
___________________________ [1]
(ii) Name the product formed at the
anode _______________
cathode _____________ [2]
g)
The electrolysis of dilute sulphuric
acid using inert electrodes produces
two gases as products.
(i) Name a material which could be used
as the electrodes in this experiment.
Graphite (or platinum)
[1]
(ii) Name the product formed at the
anode oxygen [1] accept O2
cathode hydrogen [1] accept H2
(iii) Write balanced, ionic equations
to show how these gases are
formed.
Anode reaction
______________[2]
Cathode reaction
_____________[2]
(iii) Write balanced, ionic equations to
show how these gases are formed.
Anode reaction
2H2O → O2 + 4H+ + 4eor 4OH- → 2H2O + O2 + 4eor 4OH- → 4e- + 2H2O + H2
[2]
Cathode reaction
2H+ + 2e- → H2
[2]
2002,Paper 1
4 a) What term is used to describe a
reaction which gives out heat?
__________________________ [1]
4 a) What term is used to describe a
reaction which gives out heat?
Exothermic
[1]
b)
(i)
When drops of water are added to
anhydrous copper sulphate heat is given
out.
Describe what would be observed during
this reaction.
_________________________________
______________________________ [2]
(ii) The addition of water to anhydrous
copper sulphate is called
______________________________ [1]
b)
When drops of water are added to
anhydrous copper sulphate heat is given
out.
(i)
Describe what would be observed during
this reaction.
The white [1] solid would turn blue [1]
(ii) The addition of water to anhydrous
copper sulphate is called
Hydration
[1]
c)
Heat is also given out during the reaction
of sodium hydroxide with hydrochloric
acid.
(i)
Give a balanced symbol equation for this
reaction.
______________________________ [2]
(ii) The reaction of an acid with an alkali is
called ________________________ [1]
c)
Heat is also given out during the reaction
of sodium hydroxide with hydrochloric
acid.
(i)
Give a balanced symbol equation for this
reaction.
NaOH + HCl → NaCl + H2O
[2]
(ii) The reaction of an acid with an alkali is
called Neutralisation
[1]
d)
(i)
The redox reaction of zinc with copper
sulphate solution also gives out heat.
Describe what would be observed during
this reaction.
_________________________________
______________________________ [2]
(ii) Give a balanced symbol equation for this
equation. _____________________ [2]
d)
(i)
The redox reaction of zinc with copper sulphate
solution also gives out heat.
Describe what would be observed during this
reaction.
The silvery/grey[1] zinc would become
coated with red/brown[1] copper metal.
The blue [1] solution fades / colourless /
zinc disappears / bubbles[1] / green[1].
Max [2]
(ii) Give a balanced symbol equation for this
equation.
Zn + CuSO4 → ZnSO4 + Cu
or Zn + Cu2+ → Zn2+ + Cu
[2]
(iii) The reaction of zinc with copper
sulphate solution is an example of
______________________________ [1]
(iv) Explain this redox reaction in terms of
electron transfer.
_________________________________
_________________________________
_________________________________
______________________________ [5]
(iii) The reaction of zinc with copper
sulphate solution is an example of
Displacement
[1]
(iv) Explain this redox reaction in terms of
electron transfer.
The zinc has lost electrons [1] and is
therefore oxidised [1]. The copper ions
have gained electrons [1] and are
therefore reduced [1]. Redox is reduction
and oxidation taking place together [1]
2003, Paper 2
1
Aluminium is the most abundant
metallic element in the Earth’s crust,
making up approximately 8% of the
crust. The ore is first purified and
the metal is then extracted from the
purified ore by electrolysis.
a)
Explain what you understand by the
term “electrolysis”.
______________________________
___________________________ [2]
b) Name the ore from which aluminium
is extracted.
___________________________ [1]
a)
Explain what you understand by the
term “electrolysis”.
Electrolysis is the breaking down /
decomposing / splitting of a substance by
passing electricity through it.
[2]
b) Name the ore from which aluminium
is extracted.
Bauxite – accept alumina
[1]
c)
The electrolysis of the purified ore is
carried out in the Hall-Héroult cell.
In this cell the anode and cathode are
made of graphite. The electrolyte is
molten aluminium oxide dissolved in
cryolite, Na3AlF6.
(i) Explain what is meant by each of the
terms below:
Anode _____________________ [1]
Cathode ___________________ [1]
Electrolyte _________________ [2]
(i) Explain what is meant by each of the
terms below:
Anode is the positive electrode [1]
Cathode is the negative electrode [1]
Electrolyte is the substance through
which the electricity passes [1] and is
broken down
[1]
(ii) Give two reasons why graphite is a
suitable material from which to
make the anode and cathode.
_____________________________
__________________________ [2]
(iii) Why is the aluminium oxide
dissolved in molten cryolite?
__________________________ [2]
(ii) Give two reasons why graphite is a
suitable material from which to make the
anode and cathode.
Graphite is a good conductor [1] and is cheaper
(than platinum)/inert [1]
(iii) Why is the aluminium oxide dissolved in
molten cryolite?
The molten cryolite lowers the melting point of
the aluminium oxide / so reducing costs / saving
energy [1] increase conductivity [1]
d)(i)Name the products formed a the
electrodes during electrolysis and
give balanced, ionic equations for
the reactions taking place.
Anode
Name of
Product
Balanced
ionic equation
Cathode
d)(i)Name the products formed a the
electrodes during electrolysis and
give balanced, ionic equations for
the reactions taking place.
Anode
Cathode
Name of
Product
Oxygen [1]
Aluminium [1]
Balanced
ionic equation
2O2- → O2 + 4e- [1]
6O2- → 3O2 + 12e[2]
Al3+ 3e- → Al [2]
Or
4Al3+ + 12e- → 4Al [2]
(ii) At which electrode is reduction
taking place? Explain your answer.
_____________________________
_____________________________
__________________________ [3]
(ii) At which electrode is reduction
taking place? Explain your answer.
Reduction is taking place at the
cathode [1]. Reduction is the gain of
the electrons [1] the aluminium ions
are gaining electrons [1]
e)
Aluminium is an extremely
important metal with widespread
uses. Give two uses of aluminium
and the property on which each use
depends.
Use ______________________ [1]
Property __________________ [2]
Use ______________________ [1]
Property __________________ [2]
e)
Aluminium is an extremely important
metal with widespread uses. Give two uses
of aluminium and the property on which
each use depends.
Use overhead power cables
[1]
Property low density / good conductor [1]
Use Alloy
[1]
Property low density (but high strength) [1]
Use saucepans
[1]
Property good thermal conductor
[1]
f)
Aluminium is widely recycled.
Suggest two reasons why
aluminium metal is recycled.
_____________________________
__________________________ [2]
f)
Aluminium is widely recycled.
Suggest two reasons why
aluminium metal is recycled.
Aluminium is expensive to extract
from its ore/cheaper to recycle [1]
Bauxite reserves are running
out/reduces landfill [1]
2004, Paper 2
6a) The diagram below shows the apparatus
used to carry out the electrolysis of molten
lithium bromide using graphite electrodes.
(i)
What is meant by the term electrolysis?
_______________________________
_______________________________ [2]
(ii) During the electrolysis of molten lithium
bromide, what would be observed at the
anode?
_______________________________
_______________________________ [2]
(i)
What is meant by the term electrolysis?
Decomposition/breakdown [1] of
compounds using (a direct current of)
electricity [1]
[2]
(ii) During the electrolysis of molten lithium
bromide, what would be observed at the
anode?
Anode = brown [1] pungent [1] gas [1]
evolved. Any two
[2]
(iii) Write a balanced ionic equation for the
reaction occurring at the anode.
_______________________________ [3]
(iv) Explain as fully as possible why the bulb
does not light when the lithium bromide is
solid.
_______________________________
_______________________________
_______________________________ [3]
(iii) Write a balanced ionic equation for the
reaction occurring at the anode.
Anode = 2Br- → Br2 + 2e[3]
(iv) Explain as fully as possible why the bulb
does not light when the lithium bromide is
solid.
Ions [1] cannot move [1] when solid so no
flow of current / conduction / circuit
incomplete [1]
[3]
b)
The diagram below shows the apparatus
used to carry out the electrolysis of dilute
sulphuric acid using platinum electrodes.
Hydrogen gas and oxygen gas are evolved.
(i)
Give two reasons why platinum is used for
the electrodes.
_______________________________
_______________________________ [2]
(ii) Write a balanced ionic equation for the
reaction occurring at the anode.
_______________________________ [3]
(i)
Give two reasons why platinum is used for
the electrodes.
Conducts electricity [1] inert/does not
react with acid
[2]
(ii) Write a balanced ionic equation for the
reaction occurring at the anode.
Anode = 4OH- → O2 + 2H2O + 4e- [3]
(iii) Describe the test you could use to confirm
the presence of:
Oxygen Gas ________________________
_______________________________ [2]
Hydrogen Gas ______________________
_______________________________ [2]
(iii) Describe the test you could use to confirm
the presence of:
Oxygen Gas glowing splint [1] relights [1]
Hydrogen Gas lit splint [1] pops/explosion
[1]
2005, Paper 2
4a) Aluminium is a reactive metal which is
difficult to extract from its ore. Before
1886 it was made by heating aluminium
chloride with sodium.
Aluminium chloride + sodium → aluminium + sodium chloride
(i)
Write a balanced symbol equation for this
reaction.
_______________________________ [2]
(ii) Suggest a metal which could be used
instead of sodium.
_______________________________ [1]
(i)
Write a balanced symbol equation for this
reaction.
AlCl3 + 3Na → Al + 3NaCl
[2]
(ii) Suggest a metal which could be used
instead of sodium.
K/Mg/Ca
[1]
b)
Today, aluminium is produced industrially
by electrolysis of dissolved pure
aluminium oxide, as shown in the diagram
below. Pure aluminium oxide has a
melting point of 2050°C.
(i)
Name parts A, B and C and substances D
and E.
A __________________________
B __________________________
C __________________________
D __________________________
E __________________________ [5]
(i)
Name parts A, B and C and substances D
and E.
A anode/positive electrode [1]
B steel cell/tank [1]
C cathode/negative electrode [1]
D aluminium [1]
E cryolite [1]
(ii) What is the formula for aluminium oxide?
_______________________________ [1]
(iii) Suggest one purpose of the crust of
aluminium oxide.
_______________________________ [1]
(iv) At what temperature does the electrolysis
take place?
_______________________________ [1]
(ii) What is the formula for aluminium oxide?
Al2O3
[1]
(iii) Suggest one purpose of the crust of
aluminium oxide.
Keeps heat in/keeps impurities out/stops
oxygen reacting with Al
[1]
(iv) At what temperature does the electrolysis
take place?
700-1000°C
[1]
(v) Explain why the mixture will only conduct
electricity when molten.
_______________________________
_______________________________ [2]
(vi) Why is it uneconomical to electrolyse pure
aluminium oxide?
_______________________________ [1]
(v) Explain why the mixture will only conduct
electricity when molten.
So that the ions [1] can move [1] and carry
electricity
(vi) Why is it uneconomical to electrolyse pure
aluminium oxide?
Due to high melting point
[1]
(vii) Name the product at the negative electrode
and give an ionic equation for its
production.
Name of product ____________________
Ionic equation ___________________ [3]
(viii)Which electrode must be replaced
regularly? Explain your answer using a
symbol equation.
Electrode __________________________
Equation ________________________ [3]
(vii) Name the product at the negative electrode
and give an ionic equation for its
production.
Name of product Aluminium
[1]
Ionic equation Al3+ + 3e- → Al
[2]
(viii)Which electrode must be replaced
regularly? Explain your answer using a
symbol equation.
Electrode Anode
[1]
Equation C + O2 → CO2
[2]
c)
The statue of Eros
in London’s
Piccadilly Circus
has been in place
for about 100
years. It is made
of aluminium and
has shown
virtually no
damage from
corrosion .
Aluminium is used
today for overhead
electricity cables.
(i)
Why is aluminium resistant to corrosion?
_______________________________
_______________________________ [3]
(ii) Give one property which aluminium must
have if it is used for overhead power
cables.
_______________________________ [1]
(i)
Why is aluminium resistant to corrosion?
protective [1] oxide [1] layer [1]
[3]
(ii) Give one property which aluminium must
have if it is used for overhead power
cables.
Conducts electricity/relatively low density
2006, Paper 2
5a) The following reactions A and B can be
classified in different ways.
A copper(II) carbonate → copper (II) oxide + carbon dioxide
B sodium hydroxide + hydrochloric acid → sodium chloride + water
Complete the table by placing a (√) in each column for
reactions A and B indicating which terms apply to each
reaction. More than one term can be applied to each reaction.
A copper(II) carbonate → copper (II) oxide + carbon dioxide
B sodium hydroxide + hydrochloric acid → sodium chloride + water
Term
Exothermic
Endothermic
Thermal decomposition
Thermal cracking
Combustion
Neutralisation
Displacement
Reaction
A
B
Complete the table by placing a (√) in each column for
reactions A and B indicating which terms apply to each
reaction. More than one term can be applied to each reaction.
Term
Reaction
A
√ [1]
Exothermic
Endothermic
B
√ [1]
Thermal decomposition √ [1]
Thermal cracking
Combustion
Neutralisation
Displacement
√ [1]
b)
Solid copper(II) oxide can be reduced by
passing a stream of hydrogen gas over the
heated solid.
(i)
Write a balanced symbol equation for the
reaction between copper(II) oxide and
hydrogen gas.
_______________________________ [2]
(ii) What would you observe during this
reaction?
_______________________________
_______________________________ [2]
(i)
Write a balanced symbol equation for the
reaction between copper(II) oxide and
hydrogen gas.
CuO + H2 → Cu + H2O
[1]
[1]
[2]
(ii) What would you observe during this
reaction?
Black [1] solid turns pink/brown [1] flame
diminishes in size [1] drops of colourless
liquid [1]. Accept condensation. Max [2]
(iii) Write a balanced symbol equation for the
hydrogen burning.
_______________________________ [3]
(iii) Write a balanced symbol equation for the
hydrogen burning.
2H2 + O2 → 2H2O
[3]
[1]
[1] +[1] for balancing
c)
The table below gives a series of equations
for oxidation and reduction reactions in
two industrial processes.
Reaction Equation
A
B
2O2- → O2 + 4e-
C
S + O2 → SO2
D
2SO2 + O2 → 2SO3
Type
Industrial Process
Reduction Aluminium
manufacture by
Oxidation electrolysis
Oxidation Sulphuric Acid
Oxidation manufacture
c)
The table below gives a series of equations
for oxidation and reduction reactions in
two industrial processes.
Reaction Equation
Type
A
Al3+ + 3e- → Al
[1]
[1]
+[1] for balancing
Reduction
B
2O2- → O2 + 4e-
Oxidation
C
S + O2 → SO2
Oxidation
D
2SO2 + O2 → 2SO3
Oxidation
Industrial
Process
Aluminium
manufacture
by
electrolysis
Sulphuric
Acid
manufacture
(i)
Complete the table giving the reduction
reaction in the industrial manufacture of
aluminium.
(ii) Explain why reaction C is described as
oxidation.
_______________________________
_______________________________ [2]
(i)
Complete the table giving the reduction
reaction in the industrial manufacture of
aluminium.
(ii) Explain why reaction C is described as
oxidation.
Sulphur gains oxygen [1] gain of oxygen
is oxidation [1]
[2]
(iii) What is the name of the process for the
industrial manufacture of sulphuric acid?
_______________________________ [1]
(iv) Name the catalyst used in reaction D.
_______________________________ [1]
(iii) What is the name of the process for the
industrial manufacture of sulphuric acid?
Contact Process
[1]
(iv) Name the catalyst used in reaction D.
Vanadium(V) oxide/vanadium
pentoxide/V2O5
[1]
2006, Paper 2
6
Ionic compounds like lead(II) bromide
conduct electricity when molten.
a)
Explain as fully as possible why ionic
compounds conduct electricity when
molten.
_______________________________
_______________________________
_______________________________ [2]
6
Ionic compounds like lead(II) bromide
conduct electricity when molten.
a)
Explain as fully as possible why ionic
compounds conduct electricity when
molten.
Ions [1] (free to) move/carry charge [1] [2]
b)(i) Draw a labelled diagram of the assembled
apparatus used to carry out the electrolysis
of molten lead(II) bromide.
[5]
b)(i) Draw a labelled diagram of the assembled
apparatus used to carry out the electrolysis
of molten lead(II) bromide.
Individual marks are given for correctly
labelled and recognisable drawing.
Complete circuit with electrodes in molten
electrolyte [1] anode/positive electrode [1],
cathode/negative electrode [1],
crucible/evaporating basin/beaker, molten
lead(II) bromide/electrolyte [1], tripod [1],
bunsen burner/heat [1]. (No labels = no
marks) (Maximum [5])
(ii) Name the material used to make the
electrodes in this electrolysis.
_______________________________ [1]
(iii) What would be observed at the positive
electrode during the experiment?
_______________________________ [2]
(ii) Name the material used to make the
electrodes in this electrolysis.
Graphite/carbon
[1]
(iii) What would be observed at the positive
electrode during the experiment?
Red/brown [1] pungent [1] fumes/gas [1]
(Maximum [2])
(iv) Name the products of this electrolysis.
_______________________________ [2]
(v) Why does this electrolysis experiment
need to be carried out in a fume cupboard?
_______________________________ [2]
(iv) Name the products of this electrolysis.
Lead (metal) [1] bromine [1]
[2]
(v) Why does this electrolysis experiment
need to be carried out in a fume cupboard?
Toxic [1] nature of bromine/lead [1] [2]
c)
The diagram below shows the apparatus
used in the refining of copper by
electrolysis.
(i)
What material is used for the anode?
_______________________________ [2]
(ii) Write a balanced, ionic equation for the
reaction which takes place at the anode.
_______________________________ [3]
(i)
What material is used for the anode?
Impure [1] copper [1]
[2]
(ii) Write a balanced, ionic equation for the
reaction which takes place at the anode.
Anode: Cu → Cu2+ + 2e[3]
[1]
[1] +[1] for balancing
(iii) Name one substance which may be used as
the electrolyte.
_______________________________ [1]
(iii) Name one substance which may be used as
the electrolyte.
Any soluble copper compounds, usually
copper sulphate
[1]
2007, Paper 2
3a)
A solution of copper(II) sulphate is used as the
electrolyte in the refining of copper metal.
Impure copper is used as the anode. A piece of
pure copper is used as the cathode.
(i)
What terms should be used
to label the diagram at the
points shown?
A _____________________________ [1]
B _____________________________ [1]
(ii) Explain what is meant by the term
electrolyte.
_______________________________
_______________________________
_______________________________ [3]
(i)
What terms should be used to label the
diagram at the points shown?
A anode/impure copper
B cathode/pure copper
[1]
[1]
(ii) Explain what is meant by the term
electrolyte.
A liquid [1] which conducts electricity [1]
and decomposes [1]
[3]
(iii) Explain, in terms of the particles involved,
why the lamp lights when the circuit is
connected as shown above.
_______________________________
_______________________________
_______________________________ [3]
Quality of written communication
[2]
(iii) Explain, in terms of the particles involved,
why the lamp lights when the circuit is
connected as shown above.
Solution contains ions [1] which can move
[1] and carry charge/complete circuit [3]
Quality of written communication
[2]
(iv) State one use of copper metal.
_______________________________ [1]
(iv) State one use of copper metal.
(electrical) wiring/plumbing/brass /
coinage/roofing/pipes/and any suitable [1]
b)
The table below details the changes which
occur during the electrolysis of
concentrated sodium chloride solution
using titanium electrodes.
(i)
Complete the table giving the colour and
physical state of the product formed at the
anode and give the half equation for the
ionic reaction occurring at the cathode.
Electrode Observations
Half Equation
Colour
Anode
2Cl- → Cl2 + 2eState
Colour
Colourless
Cathode
State
Gas
(i)
Complete the table giving the colour and
physical state of the product formed at the
anode and give the half equation for the
ionic reaction occurring at the cathode.
Electrode Observations
Half Equation
Colour Green/yellow-green
[1]
Anode
2Cl- → Cl2 + 2eGas [1]
State
Colour Colourless
2H+ + 2e- → H2 [3]
Cathode
State
Gas
(ii) Suggest one reason why titanium is a good
material to use for the electrodes
_______________________________ [1]
(ii) Suggest one reason why titanium is a good
material to use for the electrodes
conducts electricity / unreactive
[1]
c)
Aluminium is extracted from its ore by the
electrolysis of a molten mixture containing
aluminium oxide. The molten mixture
also contains a substance called cryolite
which reduces the temperature required
from over 2000°C to around 900°C
(i)
What is the name of the main ore of
aluminium?
_______________________________ [1]
(ii) Write a balanced symbol equation for the
production of aluminium and oxygen from
aluminium oxide.
_______________________________ [3]
(i)
What is the name of the main ore of
aluminium?
bauxite [1]
[1]
(ii) Write a balanced symbol equation for the
production of aluminium and oxygen from
aluminium oxide.
2Al2O3 → 4Al + 3O2
[3]
[1]
[1]
+[1] for balancing
(iii) State one other purpose of the cryolite in
the process.
_______________________________ [1]
(iv) Name one other metal which is extracted
from its ore by electrolysis.
_______________________________ [1]
(iii) State one other purpose of the cryolite in
the process.
Increases conductivity
[1]
(iv) Name one other metal which is extracted
from its ore by electrolysis.
Any metal above aluminium in the
reactivity series lithium, potassium,
sodium, calcium, magnesium
[1]
(i)
What name did Newlands give to the
repeating pattern observed in the
properties of the elements?
_______________________________ [1]
(ii) Which group of elements, present in the
modern Periodic Table, is missing from
Newlands’ table above?
_______________________________ [1]
Thanks for viewing.
Do consider using others in this Series of Ten.
112