Electrolysis
CPG Paper
1. Copper can be purified using electrolysis. The diagram below shows the apparatus used.
a) Explain why copper sulphate solution is able to conduct electricity. (1 mark)
b) At the cathode, pure copper forms copper ions.
What type of reaction is taking place here? Explain your answer. (1 mark)
c) During the electrolysis the impure copper anode dissolves. Write the half equation
for the reaction at the anode. (1 mark)
d) Give a common use of the pure copper produced. (1 mark)
e) Copper is a transition metal. Describe two physical properties that are characteristic
of transition metals. (2 marks)
f) Copper is only purified for certain uses because the purification process is
expensive. Suggest a reason why the purification of copper is expensive.
(1 mark)
Sample Paper
2.
a) Sulphuric acid is used to make copper sulphate, which is used in the purification of copper. Copper sulphate can be made by warming copper oxide with sulphuric acid. The equation for the reaction is
CuO + H2SO4 → CuSO4 + H2O
Calculate the maximum mass of copper oxide which can react with 9.8g sulphuric
acid in this reaction. [Relative atomic masses H = 1; O = 16; S = 32; Cu = 64]
(5 marks)
b) (i) Draw a labelled diagram of a cell which could be used to produce pure copper
from a strip of impure copper. (4 marks)
(ii) Complete the equation for the reaction taking place at the cathode of the cell.
Cu2+ (aq) + ______→ Cu(s) (1 mark)
(iii) Explain why this reaction can be described as reduction of copper ions.
(1 mark)
June 2009
3. Copper is used top make water pipes and in the electronics industry.
a) Describe two properties of copper or its compounds that are typical of transition metals and their compounds (2 marks)
b) Very pure copper is produced from impure copper by electrolysis. The
diagram shows a cell in which impure copper is the anode and the cathode is stainless steel.
i) Identify the electrolyte used in the cell. (1 mark)
ii) Describe what happens to the impure copper electrode during electrolysis.
(1 mark)
iii) Describe what happens at the negative electrode (2 marks)
iv) During the electrolysis, impurities collect below the positive electrode.
Explain the importance of these impurities. (2 marks)
June 2008
4. Copper is a red-brown metal. It has a melting point of 1085oC. It is used to
make electrical wires and compounds of copper are often blue.
a) Copper is in the middle section of the periodic table. What is the name given to the elements in this part of the table? (1 mark)
b) Using only the information above, state two properties of copper typical of elements found in this part of the periodic table. (2 marks)
c) The diagram shows the apparatus used to purify copper.
i) Name the electrolyte used. (1 mark)
ii) What would you see happening at the cathode (1 mark)
iii) In terms of electrons, what happens to the copper ions at the cathode?
(1 mark)
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