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Constructed Response Topic 11: Redox and electrochemistry
Set A: Voltaic cell, electrolytic cell, half reaction equation, oxidation numbers
Base your answers to questions 1 though 4 on the following information.
Aluminum is one of the most abundant metals in Earth’s crust. The aluminum
compound found in bauxite ore is Al2O3. Over one hundred years ago, it was
difficult and expensive to isolate aluminum from bauxite ore. In 1886, a brother
and sister team, Charles and Julia Hall, found that molten (melted) cryolite, Na3AlF6,
would dissolve bauxite ore. Electrolysis of the resulting mixture caused the aluminum
ions in the Al2O3 to be reduced to molten aluminum metal. This less expensive
process is known as the Hall process.
1. Explain, in terms of electrical energy, how the 1.
operation of a voltaic cell differs from the operation
of an electrolytic cell used in the Hall process. Include
both voltaic cell and electrolytic cell in your answer.
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2. Explain, in terms of ions, why molten cryolite conducts 2.
electricity.
3. Write a balance half-reaction equation for the reduction 3.
3+
of Al to Al
4. Write the oxidation state for each of the elements in 4.
cryolite.
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Set B: Balancing redox equation, writing half-reaction equations
Base your answers to questions 5 and 6 on the unbalanced redox reaction below.
__Cu(s) + __ AgNO3(aq) ----- > __ Cu(NO3)2(aq) + __ Ag(s)
5. Balance the redox equation using the smallest whole number coefficients.
6. Write half-reaction equations for 6. Oxidation half:
oxidation and reduction that occur
in the above reaction.
Reduction half :
Set C: Writing half -reaction equation, determining oxidation number
Base your answers to questions 7 and 8 on the equation below.
4 Al(s) + 3O2(g) ------ > 2 Al2O3 (s)
7. Write a balance oxidation half-reaction equation 7.
for this reaction.
8. What is the oxidation number of oxygen in Al2O3? 8.
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 407
Constructed Response Topic 11: Redox and electrochemistry
Set A: Voltaic cell, electrolytic cell, half reaction equation, oxidation numbers
Base your answers to questions 1 though 4 on the following information.
Aluminum is one of the most abundant metals in Earth’s crust. The aluminum
compound found in bauxite ore is Al2O3. Over one hundred years ago, it was
difficult and expensive to isolate aluminum from bauxite ore. In 1886, a brother
and sister team, Charles and Julia Hall, found that molten (melted) cryolite, Na3AlF6,
would dissolve bauxite ore. Electrolysis of the resulting mixture caused the aluminum
ions in the Al2O3 to be reduced to molten aluminum metal. This less expensive
process is known as the Hall process.
1. Explain, in terms of electrical energy, how the 1.
operation of a voltaic cell differs from the operation
of an electrolytic cell used in the Hall process. Include
both voltaic cell and electrolytic cell in your answer.
Teacher Preview Copy
2. Explain, in terms of ions, why molten cryolite conducts 2.
electricity.
3. Write a balance half-reaction equation for the reduction 3.
3+
of Al to Al
4. Write the oxidation state for each of the elements in 4.
cryolite.
Teacher Preview Copy
Set B: Balancing redox equation, writing half-reaction equations
Base your answers to questions 5 and 6 on the unbalanced redox reaction below.
__Cu(s) + __ AgNO3(aq) ----- > __ Cu(NO3)2(aq) + __ Ag(s)
5. Balance the redox equation using the smallest whole number coefficients.
6. Write half-reaction equations for 6. Oxidation half:
oxidation and reduction that occur
in the above reaction.
Reduction half :
Set C: Writing half -reaction equation, determining oxidation number
Base your answers to questions 7 and 8 on the equation below.
4 Al(s) + 3O2(g) ------ > 2 Al2O3 (s)
7. Write a balance oxidation half-reaction equation 7.
for this reaction.
8. What is the oxidation number of oxygen in Al2O3? 8.
Copyright©2010 E3 Scholastic Publishing. All Rights Reserved. SurvivingChem.com 407
