9. Metals
A section of Chemistry, 0620
Listing 10 of 1272 questions
Gallium and aluminium are in Group III of the Periodic Table. The melting point of gallium is 30 °C. Use the kinetic particle theory to explain what happens when a spoon made of gallium is put into a cup of tea at 40 °C. In your answer, refer to: ● the change of state which occurs, ● the change in the arrangement of the particles, ● the change in the motion of the particles. Gallium burns in air at a high temperature to form gallium(oxide. Complete the symbol equation for this reaction. Ga + 3O2 → Ga2O3 Explain why aluminium is often used in containers for food and drinks. Aluminium chloride can be made by heating aluminium foil in a stream of chlorine. chlorine aluminium foil aluminium chloride On the diagram above, draw an arrow to show where heat should be applied. At temperatures between 178 °C and 400 °C, aluminium chloride has the structure shown below. Cl Al Cl Cl Cl Cl Al Cl Deduce the molecular formula of this structure. Some properties of aluminium and silver are shown in the table below. cost density in g / cm3 electrical conductivity melting point / °C aluminium high 2.7 good silver very high 10.5 very good Use the information in the table to suggest why aluminium rather than silver is used in overhead power cables.
0620_w14_qp_22
THEORY
2014
Paper 2, Variant 2
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Aluminium is obtained by the reduction of aluminium ions to aluminium atoms. Write an ionic equation for the reduction of an aluminium ion to an aluminium atom. The original method of extracting aluminium involved the reduction of aluminium chloride using the reactive metal sodium. Aluminium obtained by this method was very expensive due to the high cost of extracting sodium from sodium chloride. Complete the equation for this reduction. Al Cl 3 + Na → + How can sodium metal be obtained from sodium chloride? In the modern method, aluminium is obtained by the electrolysis of aluminium oxide dissolved in molten cryolite, Na3Al F6. carbon cathode (–) carbon anode (+) mixture of aluminium oxide and cryolite molten aluminium waste gases, O2, CO2, CO, F2 The major ore of aluminium is impure aluminium oxide. What is the name of this ore? This ore is a mixture of aluminium oxide, which is amphoteric, and iron(oxide which is basic. Explain how these two oxides can be separated by the addition of aqueous sodium hydroxide. Give two reasons why the electrolyte contains cryolite. The mixture of gases evolved at the positive electrode includes: carbon dioxide carbon monoxide fl uorine oxygen Explain the presence of these gases in the gaseous mixture formed at the positive electrode. Include at least one equation in your explanation. A major use of aluminium is the manufacture of pots and pans. One reason for this is its resistance to corrosion. Explain why aluminium, a reactive metal, is resistant to corrosion. Suggest two other reasons why aluminium is suitable for making pots and pans.
0620_w14_qp_32
THEORY
2014
Paper 3, Variant 2
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Questions Discovered
1272