9. Metals
A section of Chemistry, 0620
Listing 10 of 1272 questions
Iron pyrite, FeS2, is known as Fool’s Gold because it is a shiny yellow solid which is similar in appearance to gold. Iron pyrite is an ionic compound. Gold is a metallic element. Iron pyrite, FeS2, contains positive and negative ions. The positive ion is Fe2+. Deduce the formula of the negative ion. A student is provided with a sample of iron pyrite and a sample of gold. Suggest how the student could distinguish between the two substances. Sulfur dioxide is produced on a large scale by heating iron pyrite strongly in air. The iron pyrite reacts with oxygen in the air producing iron(oxide, Fe2O3, and sulfur dioxide. Construct a chemical equation for the reaction between iron pyrite and oxygen. Give one use of sulfur dioxide.
0620_m16_qp_42
THEORY
2016
Paper 4, Variant 2
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The diagram shows a blast furnace for extracting iron. mixture of iron ore, coke and limestone (calcium carbonate) slag molten iron On the diagram write ● the letter A to show where air is blown into the furnace, ● the letter W to show where waste gases exit the furnace. How do you know from the information in the diagram that slag is less dense than molten iron? Limestone (calcium carbonate) is one of the raw materials added to the blast furnace. Calcium carbonate undergoes thermal decomposition in the blast furnace. What is meant by the term thermal decomposition? Complete the chemical equation for this reaction. CaCO3 CaO + A further reaction in the blast furnace involves calcium oxide, CaO. Describe this reaction and explain its importance. Pure iron can be prepared by electrolysis of an aqueous solution of a suitable iron(salt. Draw a labelled diagram of an electrolysis cell that could be used to carry out this reaction. In your diagram include ● the electrodes, ● the electrolyte, ● the power supply. State the name of an element that could be used for the electrodes. State one property that an electrode should have. Pure iron can also be prepared by the thermal decomposition of iron pentacarbonyl. The structure of iron pentacarbonyl is shown. Fe C C C C C O O O O O Write the formula for iron pentacarbonyl. The word equation for the reaction is shown. iron pentacarbonyl iron + carbon monoxide Explain why the gaseous product is hazardous. The rate of rusting of iron varies with pH and temperature. What two substances must be in contact with iron for it to rust? The graph shows the rate of rusting at different pH values and temperatures. mass of rust / g time / hours pH 4, 30 °C pH 4, 20 °C pH 7, 30 °C pH 8, 30 °C pH 7, 20 °C pH 8, 20 °C How do pH and temperature affect the rate of rusting? pH temperature
0620_m17_qp_32
THEORY
2017
Paper 3, Variant 2
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Silver dichromate, Ag2Cr2O7, is a red insoluble salt. Silver dichromate can be made by reacting silver nitrate solution with ammonium dichromate solution. The chemical equation for the reaction is shown. 2AgNO3+ (NH4)2Cr2O72NH4NO3+ Ag2Cr2O7Describe how you could obtain pure dry solid silver dichromate after mixing silver nitrate solution and ammonium dichromate solution. The charge on a silver ion is +1. Deduce the charge on the dichromate ion in Ag2Cr2O7. Write the ionic equation for the formation of silver dichromate in this reaction. State symbols are not required. Dilute aqueous sodium hydroxide was added to the ammonium nitrate solution made in the reaction. The mixture was then warmed and damp Universal Indicator paper was held above the mixture. State and explain what would happen to the Universal Indicator paper. The apparatus shown was set up. solid silver nitrate solid ammonium dichromate plastic trough water S After five minutes, a red solid appeared along the line marked S on the diagram. Explain why a red solid appeared along the line marked S. The experiment was repeated at a higher temperature. What effect, if any, would this have on the time taken for the red solid to appear? Explain your answer. Ammonium dichromate, (NH4)2Cr2O7, undergoes thermal decomposition. The products are chromium(oxide, nitrogen and water. What is meant by thermal decomposition? Write a chemical equation for the thermal decomposition of ammonium dichromate.
0620_m17_qp_42
THEORY
2017
Paper 4, Variant 2
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Iron is extracted from its ore using a blast furnace. In the blast furnace, coke burns in oxygen to produce heat energy and carbon dioxide. How is this carbon dioxide converted into carbon monoxide in the blast furnace? Calcium carbonate added to the blast furnace decomposes to form calcium oxide. Calcium oxide removes silicon(oxide impurities from the iron in a neutralisation reaction. Write a chemical equation for the reaction of calcium oxide with silicon(oxide. Suggest why it is a neutralisation reaction. The main impurity in iron obtained from the blast furnace is carbon. Why must the high levels of carbon be lowered before the iron becomes a useful material? How is the carbon removed from the iron? Zinc is extracted from its ore. The ore contains zinc sulfide. The zinc sulfide is roasted in air to produce zinc oxide and sulfur dioxide. Zinc is then obtained from the zinc oxide using a blast furnace. Give the name of the ore of zinc that contains zinc sulfide. Write a chemical equation for the reaction that takes place when zinc sulfide is roasted in air. Suggest why the sulfur dioxide should not be released into the atmosphere. The temperature inside the blast furnace in which zinc is extracted is about 1000 °C. The table gives some information about substances in the blast furnace in which zinc is extracted. substance melting point / °C boiling point / °C carbon sublimes at 4330 °C silicon(oxide zinc Use the data in the table to explain why the zinc obtained does not contain high levels of impurities such as silicon(oxide and carbon.
0620_m17_qp_42
THEORY
2017
Paper 4, Variant 2
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This question is about iron and its compounds. A student investigates the rate of reaction of 1 g of iron powder with 25 cm3 of hydrochloricacid of concentration 2.0 mol / dm3. The temperature is 20 °C. What effect do the following have on the initial rate of this reaction? Using hydrochloric acid of concentration 1.2 mol / dm3. All other conditions are kept the same. Using a piece of iron of mass 1 g. All other conditions are kept the same. Carrying out the experiment at 25 °C. All other conditions are kept the same. Siderite is an ore of iron. State the name of one other ore of iron. Siderite contains mainly iron(carbonate. Describe how to show that siderite contains a carbonate. Iron can be extracted from its oxide by reduction with carbon. The table shows how easy it is to reduce four metal oxides by heating with carbon. metal oxide ease of reduction with carbon bismuth(oxide only reduced above 250 °C iron(oxide only reduced above 650 °C tin(oxide only reduced above 500 °C titanium(oxide not reduced at 700 °C Use this information to put the metals in order of their reactivity. Put the least reactive metal first. least reactive most reactive  
0620_m18_qp_32
THEORY
2018
Paper 3, Variant 2
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Titanium is extracted from an ore called rutile. Rutile is an impure form of titanium(oxide, TiO2. Rutile is mixed with coke and heated in a furnace through which chlorine gas is passed. The product is gaseous titanium(chloride, TiCl 4. TiO2+ 2C+ 2Cl 2TiCl 4+ 2COThe gaseous titanium(chloride produced is condensed into the liquid state. The titanium(chloride is then separated from liquid impurities. Suggest the name of the process by which liquid titanium(chloride could be separated from the liquid impurities. Carbon monoxide, CO, is also produced in the reaction. Why should carbon monoxide not be released into the atmosphere? Calculate the volume of chlorine gas, Cl 2, at room temperature and pressure, that reacts completely with 400 g of TiO2using the following steps. TiO2+ 2Cl 2+ 2CTiCl 4+ 2CO● ● Calculate the relative formula mass, Mr, of TiO2.  Mr of TiO2 = ● ● Calculate the number of moles in 400 g of TiO2.  mol ● ● Determine the number of moles of Cl 2 that react with 400 g of TiO2.  moles of Cl 2 = mol ● ● Calculate the volume of Cl 2 that reacts with 400 g of TiO2.  volume of Cl 2 = dm3  Titanium(chloride, TiCl 4, is heated with an excess of magnesium, in an atmosphere of argon. Balance the chemical equation for the reaction. TiCl 4 + Mg Ti + MgCl 2  Titanium(chloride can be reacted with sodium instead of magnesium. The reaction between titanium(chloride and sodium is similar to the reaction between titanium(chloride and magnesium. Write a chemical equation for the reaction between titanium(chloride and sodium. Suggest why the reaction between titanium(chloride and magnesium is done in an atmosphere of argon and not in air. After titanium(chloride is heated with magnesium, the unreacted magnesium is removed by adding an excess of dilute hydrochloric acid to the mixture. The dilute hydrochloricacid also dissolves the magnesiumchloride. The dilute hydrochloricacid does not react with the titanium or dissolve it. Give two observations and write a chemical equation for the reaction that occurs when dilute hydrochloric acid reacts with magnesium. chemical equation  Name the process that is used to separate the titanium from the mixture after all the magnesium has been removed. Titanium does not react with the dilute hydrochloric acid or dissolve in it. Suggest why titanium does not react with dilute hydrochloric acid. Magnesium cannot be produced by electrolysis of aqueous magnesium chloride using inert electrodes. Name the product formed at the negative electrode during the electrolysis of aqueous magnesium chloride. Suggest how magnesium can be produced from magnesium chloride by electrolysis. 
0620_m19_qp_42
THEORY
2019
Paper 4, Variant 2
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Questions Discovered
1272