9. Metals
A section of Chemistry, 0620
Listing 10 of 1272 questions
For Examiner's Use The following apparatus was used to measure the rate of the reaction between zinc and iodine. 100 cm3 of aqueous iodine, 0.1 mol / dm3 at 25 oC mixture stirred by magnetic stirrer thin plate of zinc to balance The mass of the zinc plate was measured every minute until the reaction was complete. Write an ionic equation for the redox reaction that occurred between zinc atoms and iodine molecules. Describe how you could show by adding aqueous sodium hydroxide and aqueous ammonia that a solution contained zinc ions. result with sodium hydroxide excess sodium hydroxide result with aqueous ammonia excess aqueous ammonia For Examiner's Use From the results of this experiment two graphs were plotted. time time mass of plate loss of mass graph 1 graph 2 Which reagent iodine or zinc was in excess? Give a reason for your choice. Describe how the shape of graph 1 would change if 100cm3 of 0.05 mol/dm3 iodine had been used. On graph 2, sketch the shape if the reaction had been carried out using 100 cm3 of 0.1 mol/dm3 iodine at 35 °C instead of at 25 °C.
0620_s05_qp_3
THEORY
2005
Paper 3, Variant 0
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For Examiner's Use A South Korean chemist has discovered a cure for smelly socks. Small particles of silver are attached to a polymer, poly, and this is woven into the socks. Give the structural formula of the monomer. Draw the structural formula of the polymer. Suggest which one, monomer or polymer, will react with aqueous bromine and why? To show that the polymer contains silver the following test was carried out. The polymer fibres were chopped into small pieces and warmed with nitric acid. The silver atoms were oxidised to silver(ions. The mixture was filtered. Aqueous sodium chloride was added to the filtrate and a white precipitate formed. Why was the mixture filtered? Explain why the change of silver atoms to silver ions is oxidation. Give the name of the white precipitate. For Examiner's Use The unpleasant smell is caused by carboxylic acids. Bacteria cause the fats on the skin to be hydrolysed to these acids. Silver kills the bacteria and prevents the hydrolysis of the fats. Fats are esters. Give the name and structural formula of an ester. name structural formula Complete the word equation. Ester + water carboxylic acid + Propanoic acid is a weak acid. The following equation represents its reaction with ammonia. CH3 CH2 COOH + NH3 CH3 CH2 COO– + NH4 + Explain why propanoic acid behaves as an acid and ammonia as a base. Explain the expression weak acid.
0620_s05_qp_3
THEORY
2005
Paper 3, Variant 0
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For Examiner's Use The position of aluminium in the reactivity series of metals is shown below. magnesium aluminium zinc copper Aluminium is extracted by the electrolysis of its molten oxide. waste gases carbon cathode (–) carbon anode (+) mixture of aluminium oxide and cryolite aluminium 900 oC Name the main ore of aluminium. Why does the molten electrolyte contain cryolite? Oxygen is produced at the positive electrode . Name another gas which is given off at this electrode. Aluminium reacts very slowly with aqueous copper(sulphate. 2Al+ 3CuSO4Al2(SO4)3+ 3CuWhich of the two metals has the greater tendency to form ions? Describe what you would see when this reaction occurs. Explain why aluminium reacts so slowly. For Examiner's Use Complete the following table by writing “reaction” or “no reaction” in the spaces provided. oxide type of oxide reaction with acid reaction with alkali magnesium basic aluminium amphoteric Predict the equations for the decomposition of the following aluminium compounds. Al(OH)3 + aluminium nitrate + +
0620_s05_qp_3
THEORY
2005
Paper 3, Variant 0
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Use Iron is extracted from iron ore by heating the iron ore with coke and limestone. State the name of the ore from which iron is extracted. The coke burns in a blast of hot air to form carbon monoxide. Complete the equation for this reaction. C + O2 CO State an adverse effect of carbon monoxide on human health if it were to escape from the blast furnace. Near the top of the blast furnace, carbon monoxide reacts with iron ore. Fe2O3 + 3CO 2Fe + 3CO2 Write a word equation for this reaction. What type of chemical reaction is the conversion of Fe2O3 to 2Fe? Examiner's Use The limestone is converted to calcium oxide and carbon dioxide by the intense heat in the furnace. CaCO3 CaO + CO2 What type of chemical reaction is this? Name a use of limestone other than in the blast furnace. The calcium oxide reacts with silica and alumina in the iron ore. The product of this reaction collects on top of the molten iron at the bottom of the furnace. What is the name of this product? Put a ring around the correct answer. bauxite sand slag slaked lime The iron obtained from the blast furnace contains the following impurities. carbon manganese phosphorus silicon Which one of these elements is a transition element? What type of oxide is phosphorus oxide? Put a ring around the correct answer. acidic amphoteric basic neutral 50 tonnes of impure cast iron from the blast furnace contains 47 tonnes of iron. Calculate the percentage of the impurities in the cast iron.
0620_s06_qp_2
THEORY
2006
Paper 2, Variant 0
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Questions Discovered
1272