0620_s07_qp_3
A paper of Chemistry, 0620
Questions:
7
Year:
2007
Paper:
3
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0
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For Examiner's Use There are three methods of preparing salts. Method A – use a burette and an indicator. Method B – mix two solutions and obtain the salt by precipitation. Method C – add an excess of base or a metal to a dilute acid and remove the excess by filtration. For each of the following salt preparations, choose one of the methods A, B or C, name any additional reagent needed and then write or complete the equation. the soluble salt, zinc sulphate, from the insoluble base, zinc oxide method reagent word equation the soluble salt, potassium chloride, from the soluble base, potassium hydroxide method reagent equation + → KCl + H2O the insoluble salt, lead(iodide, from the soluble salt, lead(nitrate method reagent equation Pb2+ + →
7. Acids, bases and salts  →  7.3. Preparation of salts
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For Examiner's Use Use your copy of the periodic table to help you answer these questions. Predict the formula of each of the following compounds. barium oxide boron oxide Give the formula of the following ions. sulphide gallium Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound nitrogen trichloride. Use x to represent an electron from a nitrogen atom. Use o to represent an electron from a chlorine atom. Potassium and vanadium are elements in Period IV. State two differences in their physical properties. Give two differences in their chemical properties. For Examiner's Use Fluorine and astatine are halogens. Use your knowledge of the other halogens to predict the following: The physical state of fluorine at r.t.p. The physical state of astatine at r.t.p. Two similarities in their chemical properties [Total 15]
8. The Periodic Table  →  8.3. Group VII properties
8. The Periodic Table  →  8.1. Arrangement of elements
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For Examiner's Use Titanium is produced by the reduction of its chloride. This is heated with magnesium in an inert atmosphere of argon. TiCl4 + 2Mg → Ti + 2MgCl2 Explain why it is necessary to use argon rather than air. Name another metal that would reduce titanium chloride to titanium. Suggest how you could separate the metal, titanium, from the soluble salt magnesium chloride. Titanium is very resistant to corrosion. One of its uses is as an electrode in the cathodic protection of large steel structures from rusting. + – power steel oil rig which is cathode sea water contains H+, OH–, Na+, Cl–titanium anode Define oxidation in terms of electron transfer. The steel oil rig is the cathode. Name the gas formed at this electrode. Name the two gases formed at the titanium anode. and Explain why the oil rig does not rust. For Examiner's Use Another way of protecting steel from corrosion is sacrificial protection. Give two differences between sacrificial protection and cathodic protection.
9. Metals  →  9.5. Corrosion of metals
9. Metals  →  9.2. Uses of metals
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For Examiner's Use Aluminium is extracted by the electrolysis of a molten mixture that contains alumina, which is aluminium oxide, Al2O3. The ore of aluminium is bauxite. This contains alumina, which is amphoteric, and iron(oxide, which is basic. The ore is heated with aqueous sodium hydroxide. Complete the following sentences. The dissolves to give a solution of The does not dissolve and can be removed by Complete the labelling of the diagram. waste gases carbon anode (+) mixture of aluminium oxide and temperature is (–) The ions that are involved in the electrolysis are Al3+ and O2-. Write an equation for the reaction at the cathode. Explain how carbon dioxide is formed at the anode. For Examiner's Use Give an explanation for each of the following. Aluminium is used extensively in the manufacture of aircraft. Aluminium is used to make food containers. Aluminium electricity cables have a steel core.
9. Metals  →  9.6. Extraction of metals
9. Metals  →  9.4. Reactivity series
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For Examiner's Use Esters, fats and polyesters all contain the ester linkage. The structural formula of an ester is given below. C H H H H C C O O H H H H C H H H H C C Name two chemicals that could be used to make this ester and draw their structural formulae. Show all bonds. names and structural formulae Draw the structural formula of a polyester such as Terylene. Suggest a use for this polymer. For Examiner's Use Cooking products, fats and vegetable oils, are mixtures of saturated and unsaturated esters. The degree of unsaturation can be estimated by the following experiment. 4 drops of the oil are dissolved in 5 cm3 of ethanol. Dilute bromine water is added a drop at a time until the brown colour no longer disappears. Enough bromine has been added to the sample to react with all the double bonds. cooking product mass of saturated fat in 100 g of product / g mass of unsaturated fat in 100 g of product / g number of drops of bromine water margarine butter corn oil soya oil lard Complete the one blank space in the table. Complete the equation for bromine reacting with a double bond. C C + Br2 Using saturated fats in the diet is thought to be a major cause of heart disease. Which of the products is the least likely to cause heart disease? For Examiner's Use A better way of measuring the degree of unsaturation is to find the iodine number of the unsaturated compound. This is the mass of iodine that reacts with all the double bonds in 100 g of the fat. Use the following information to calculate the number of double bonds in one molecule of the fat. Mass of one mole of the fat is 884 g. One mole of I2 reacts with one mole C C . The iodine number of the fat is 86.2 g. Complete the following calculation. 100 g of fat reacts with 86.2 g of iodine. 884 g of fat reacts with g of iodine. One mole of fat reacts with moles of iodine molecules. Number of double bonds in one molecule of fat is
11. Organic chemistry  →  11.2. Naming organic compounds
11. Organic chemistry  →  11.5. Alkenes
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