MYP 10 Chemistry 2013-14
Oxidation and Reduction
Worksheet 2
Name: _________________________________ ( )
Class: _________ Date: _____________
_________________________________________________________________________________
1. Complete the following table.
Electrolytes
Ions present
Ionic equations, with state
symbols at the inert cathode
Ionic equations, with state
symbols at the inert anode
Dilute sulfuric
acid
Molten sodium
chloride
Dilute
hydrochloric acid
Aqueous
lead(II)nitrate
solution
2. Electrolysis involves the decomposition of a compound by the passage of an electric current.
(a) (i) Complete the table, which relates to the electrolysis of different solutions using inert electrodes.
(ii) Explain why the electrolysis of concentrated aqueous sodium chloride liberates hydrogen rather than
sodium at the cathode.
(iii) The electrolysis of dilute aqueous sodium chloride liberates oxygen at the anode.
Suggest why the electrolysis of concentrated aqueous sodium chloride liberates chlorine rather than
oxygen.
(b) Aqueous copper(II) sulfate was electrolysed using copper electrodes. The copper anode lost mass as
copper(II) ions were formed and the copper cathode gained mass as copper atoms were formed.
(i) State one industrial application of this electrolysis.
(ii) The results of an experiment involving the electrolysis of aqueous copper(II) sulfate are shown below.
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Use the information in the table to describe how each of the variables affects the mass of copper formed
at the cathode.
temperature
current
time
3. A solution of iodide ions reacts with a solution of iron(III)chloride to produce iodine and a solution of
iron(II)chloride.
(a) Write a half equation to show the conversion of iron(III) ions to iron(II) ions.
(b) Write a half equation to show the conversion of iodide ions to iodine.
(c) Hence write an overall ionic equation for the above reaction.
(d) In terms of electron gain or loss, explain which ion has been reduced.
4(a) Use these equations, which refer to aqueous solutions, to answer the questions that follow:
Fe(s) + Cu2+(aq)  Fe2+(aq) + Cu(s)
Cu(s) + 2Au+(aq)  Cu2+(aq) + 2Au(s)
Mg(s) + Fe2+(aq)  Mg2+(aq) + Fe(s)
(Au represents gold, which is below silver in the reactivity series)
(i) List the metals above in order of decreasing reactivity.
(ii) Define oxidation, in electronic terms, using one example from above.
(iii) Define reduction, in terms of oxidation number, using one example from above.
(iv) State and explain which is the strongest reducing agent in the examples above.
(v) State and explain which is the strongest oxidizing agent in the examples above.
(vi) Deduce whether a gold coin will react with aqueous magnesium nitrate.
(b) Sketch a diagram of a cell used to electrolyse a molten salt. Label the essential components.
(c) Describe how electrode reactions occur in an electrolytic cell and state the products at each electrode
when molten copper(II)iodide is electrolysed.
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5(a) Electrolysis can be used to obtain fluorine from molten potassium fluoride. Write an equation for the
reaction occurring at each electrode and describe the two different ways in which electricity is
conducted when the cell is in operation.
(b) In one experiment involving the electrolysis of molten potassium fluoride, 0.1 mol of fluorine was
formed. Deduce, giving a reason, the amount of potassium formed at the same time.
(c) Sodium will displace aluminium from its chloride on heating:
3Na + AlCl3  3NaCl + Al
(i) Explain, by reference to electrons, why the reaction is referred to as redox reaction.
(ii) Deduce the oxidation numbers of sodium and aluminium in the reactants and products.
6. A voltaic cell is set up with a silver reference electrode and a series of other metals immersed in an
electrolyte. The cell voltages were recorded in the table below.
Metal
Aluminium
Zinc
Iron
Copper
Silver
Cell voltage / V
2.47
1.55
1.19
0.46
0.00
(a) What is the relationship between the voltage of the cell and the position of the metal in the reactivity
series?
(b) Is the metal acting as the negative or positive electrode? Explain your answer.
(c) Construct the half-cell equations for a voltaic cell in which the metal is zinc and the electrolyte is silver
nitrate.
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