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Chemical changes - Reactivity of metals - High demand – Questions
Q1.This question is about fluorine.
(a) Calcium reacts with fluorine to produce calcium fluoride (CaF2).
Explain how oxidation and reduction have taken place in this reaction.
Write about electron transfer in your answer.
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(b) Explain why calcium fluoride has a high melting point.
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(c) Fluorine reacts with sulfur to produce sulfur hexafluoride (SF6).
S + 3F2 → SF6
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Relative formula masses, Mr: F2 = 38 SF6 = 146
Calculate the mass of sulfur hexafluoride produced when 0.950 g of fluorine is reacted with an excess of sulfur.
Give your answer to 3 significant figures.
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Mass = ____________________ g(5)
(Total 13 marks)
Q2.Iron is a metal that has many uses.
(a) Iron is extracted from iron ore. Part of the process involves reduction of the ore with carbon monoxide.
Iron ore contains iron oxide (Fe2O3).
Write a balanced equation for the reaction of iron oxide with carbon monoxide.
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(b) Explain why this reaction is a redox reaction.
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Steel is an alloy of iron. Steel is used to make cars.
After its useful life a car is taken to a scrapyard for recycling.
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(c) Suggest four benefits of recycling a car body.
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(d) Figure 1 shows an electromagnet being used to lift a car in a scrapyard.
Figure 1
An electromagnet is made up of a solenoid.
Figure 2 shows a solenoid.
Figure 2
Draw the magnetic field of the solenoid on Figure 2.(2)
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(e) In a scrapyard, an electromagnet is used to lift and release cars so they can be moved around.
Suggest two ways a solenoid could be made to lift and release cars in a scrapyard.
Explain why each suggestion would be useful in the scrapyard.
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(Total 15 marks)
Q3.The elements in Group 1 of the periodic table are metals.
(a) The elements in Group 1 are called the alkali metals.
Why are they called the alkali metals?
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(b) Explain the increase in reactivity of elements further down the group.
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(c) Lithium oxide is an ionic compound.
Draw a dot and cross diagram to show how lithium and oxygen combine to form lithium oxide.
Only show the electrons in the outer shell of each atom.
Give the charges on the ions formed.(4)
(Total 10 marks)
Q4.This question is about iron and aluminium.
(a) Iron is extracted in a blast furnace. Figure 1 is a diagram of a blast furnace.
(i) Calcium carbonate decomposes at high temperatures.
Complete the word equation for the decomposition of calcium carbonate.
calcium carbonate _____________________ +
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(ii) Carbon burns to produce carbon dioxide.
The carbon dioxide produced reacts with more carbon to produce carbon monoxide.
Balance the equation.
C(s) + CO2(g) _____ CO(g)
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(1)
(iii) Carbon monoxide reduces iron(III) oxide:
Fe2O3(s) + 3 CO(g) 2 Fe(s) + 3 CO2(g)
Calculate the maximum mass of iron that can be produced from 300 tonnes of iron(III) oxide.
Relative atomic masses (Ar): O = 16; Fe = 56
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Maximum mass = _______________ tonnes(3)
(b) Aluminium is extracted by electrolysis, as shown in Figure 2.
Figure 2
(i) Why can aluminium not be extracted by heating aluminium oxide with carbon?
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(ii) Explain why aluminium forms at the negative electrode during electrolysis.
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(iii) Explain how carbon dioxide forms at the positive electrodes during electrolysis.
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(Total 13 marks)
Q5.This question is about copper.
(a) Most of the copper extracted is used in electric circuits.
The figure below shows how impurities change the electrical conductivity of copper.
Percentage of impurities in copper
Copper extracted by smelting is about 99% pure.
The 99% pure copper produced by smelting is purified to 99.9999% pure copper by electrolysis.
Use values from the graph to explain why copper is purified to 99.9999%.
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(b) In this question you will be assessed on using good English, organising information clearly and using specialist terms where appropriate.
Read the information in the box.
Copper extraction
World demand for copper for the year 2011 was about 20 million tonnes.
World reserves of copper are estimated to be 700 million tonnes.
Most of the copper used is obtained from copper ores, which are mined.
The copper ore chalcopyrite is heated in a furnace to produce copper sulfide, CuS
The furnace is heated by burning fossil fuels.
Air is then blown through the hot copper sulfide, to produce copper and sulfur dioxide.
CuS + O2 → Cu + SO2
A scientist made the statement: ‘Copper should be recycled’.
Use the information in the box and your own knowledge and understanding to justify the scientist’s statement.
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(c) Phytomining is used to obtain copper from land that contains very low percentages of copper compounds.
Describe how copper compounds are obtained by phytomining.
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(Total 11 marks)
Q6.Titanium is used in aircraft, ships and hip replacement joints. Titanium is as strong as steel but 45% lighter, and is more resistant to acids and alkalis.
Most titanium is produced from its ore, rutile (titanium oxide), by a batch process that
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takes up to 17 days.
Titanium reactors produce about 1 tonne of the metal per day.Iron blast furnaces produce about 20 000 tonnes of the metal per hour.
(a) Give one property of titanium that makes it more useful than steel for hip replacement joints.
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(b) In the reactor magnesium is used to produce titanium. If carbon were used instead of magnesium, no titanium would be produced.
What does this tell you about the relative reactivities of carbon, magnesium andtitanium?
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(c) The use of titanium is limited because it is expensive.
Explain why titanium costs more than steel.
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(Total 6 marks)
Q7.Use the Reactivity Series of Metals on the Data Sheet to help you to answer this question.
The table gives information about the extraction of some metals.
Metal Date of discovery Main source Main extraction method
Gold Known to ancient civilisations
In the Earth as the metal itself
Physically separating itfrom the rocks it ismixed with
Zinc 1500 Zinc carbonate Reduction by carbon
Sodium 1807 Sodium chloride Electrolysis
(a) Explain why gold is found mainly as the metal itself in the Earth.
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(b) One of the reactions involved in producing zinc is represented by this equation.
ZnO + C → Zn + CO
Explain why carbon can be used to extract zinc.
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(c) Sodium is one of the most abundant metals on Earth.
Explain, as fully as you can, why sodium was not extracted until 1807.
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(Total 4 marks)
Q8.A student investigated heating metal carbonates.
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The student used the apparatus in the figure below.
The student’s results are shown in the table below.
Metalcarbonate
Colourbeforeheating
Colourafter
heatingMass beforeheating in g
Mass afterheating in g Limewater
Coppercarbonate Green Black 12.4 8.0 Turns
cloudy
Potassiumcarbonate White White 13.8
Zinccarbonate White White 12.5 8.1
(a) Explain the observations seen when heating copper carbonate.
Include the names of the substances produced.
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(b) (i) Potassium carbonate did not decompose when heated.
State why.
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(ii) Complete the table above to show the results you would expect the student to obtain.
(3)(Total 7 marks)
Q9.Iron is extracted from iron ore by heating the ore with coke in a blast furnace.
Iron ore contains iron oxide (Fe2O3).Coke contains carbon (C).
(a) (i) Explain why carbon can be used to produce iron from iron oxide.
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(ii) Balance the equation for the reaction of iron oxide with carbon.
_____ Fe2O3 + _____ C → _____ Fe + _____ CO2
(2)
(b) Two methods of extracting copper are by smelting ores and by phytomining.
Which of these two methods is likely to be the more environmentally friendly?
Give reasons for your choice.
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(Total 6 marks)
Q10.Exothermic reactions transfer energy to the surroundings.
(a) Draw a reaction profile for an exothermic reaction using the axes in Figure 1.
Show the:
• relative energies of the reactants and products• activation energy and overall energy change.
Figure 1
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(2)
(b) Combustion is an exothermic reaction.
Calculate the overall energy change for the complete combustion of one mole of methane in oxygen.
Bond Bond energy in kJ / mol
413
498
805
464
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Overall energy change = __________________ kJ / mol(3)
(c) Figure 2 shows the chemicals given to a student.
Figure 2
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The student wants to investigate the reactivity of the four metals.
Outline a plan the student could use to investigate the relative reactivity of the four metals, W, X, Y and Z.
The plan should use the fact that all four metals react exothermically with dilute sulfuric acid.
You should name the apparatus used and comment on the safe use of the chemicals.
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(d) Another student used displacement reactions to investigate the relative reactivity of the four metals, W, X, Y and Z.
The table below shows the student’s results.
Observations
Solution Metal W Metal X Metal Y Metal Z
Copper nitrateBrown layer formed on
metal
Brown layer formed on
metal
Brown layer formed on
metalNo change
Magnesium sulfate No change No change No change No change
Sulfuric acid Gas Few gas Gas No change
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bubbles produced
bubbles produced
bubbles produced
Zinc chlorideGrey layer formed on
metalNo change No change No change
Give the order of reactivity of metals, W, X, Y and Z.
Use the results in the table above to justify your answer.
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(e) The student concluded that these results could also be used to justify the order of reactivity of copper, magnesium, hydrogen and zinc.
The student is not completely correct. Use the results in the table above to explain why.
Suggest one further experiment that would provide evidence for the student’s conclusion.
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(Total 18 marks)
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