0620_w13_qp_31
A paper of Chemistry, 0620
Questions:
7
Year:
2013
Paper:
3
Variant:
1
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1
For Examiner’s Use For each of the following, name an element which matches the description. It is used as a fuel in nuclear reactors. It is the only non-metal which is a good conductor of electricity. Inert electrodes are made from this metal. This gaseous element is used to fi ll balloons in preference to hydrogen. An element which can form an ion of the type X3–. It has the same electron distribution as the calcium ion, Ca2+. The element is in Period 5 and Group VI.
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
9. Metals  →  9.2. Uses of metals
3. Stoichiometry  →  3.1. Formulae
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2
For Examiner’s Use Give three differences in physical properties between the Group I metal, potassium, and the transition element, iron. 1. 2. 3. The following metals are in order of reactivity. potassium zinc copper For those metals which react with water or steam, name the products of the reaction, otherwise write ‘no reaction’. potassium zinc copper
9. Metals  →  9.1. Properties of metals
9. Metals  →  9.4. Reactivity series
8. The Periodic Table  →  8.2. Group I properties
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3
For Examiner’s Use Ammonia is manufactured by the Haber process. N2+ 3H22NH3The forward reaction is exothermic. Describe how the reactants are obtained. Nitrogen Hydrogen The percentage of ammonia in the equilibrium mixture varies with temperature and pressure. Which pair of graphs, A, B or C, shows correctly how the percentage of ammonia at equilibrium varies with temperature and pressure? percentage NH3 at equilibrium temperature percentage NH3 at equilibrium pressure pair A percentage NH3 at equilibrium temperature percentage NH3 at equilibrium pressure pair B percentage NH3 at equilibrium temperature percentage NH3 at equilibrium pressure pair C The pair with both graphs correct is For Examiner’s Use Give a full explanation of why the pair of graphs you have chosen in is correct. Catalysts do not alter the position of equilibrium. Explain why a catalyst is used in this process.
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
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4
For Examiner’s Use 20.0 g of small lumps of calcium carbonate and 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3, were placed in a fl ask on a top pan balance. The mass of the fl ask and contents was recorded every minute. cotton wool to prevent drops of acid spray escaping flask 40 cm3 of hydrochloric acid, 2.0 mol / dm3 20.0 g of small lumps of calcium carbonate balance The mass of carbon dioxide given off was plotted against time. time mass of carbon dioxide CaCO3+ 2HCl  CaCl 2+ H2O+ CO2In all the experiments mentioned in this question, the calcium carbonate was in excess. Explain how you could determine the mass of carbon dioxide given off in the fi rst fi ve minutes. Label the graph F where the reaction rate is the fastest, S where it is slowing down and 0 where the rate is zero. Explain how the shape of the graph shows where the rate is fastest, where it is slowing down and where the rate is zero. Sketch on the same graph, the line which would have been obtained if 20.0 g of small lumps of calcium carbonate and 80 cm3 of hydrochloric acid, concentration 1.0 mol / dm3, had been used. For Examiner’s Use Explain in terms of collisions between reacting particles each of the following. The reaction rate would be slower if 20.0 g of larger lumps of calcium carbonate and 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3, were used. The reaction rate would be faster if the experiment was carried out at a higher temperature. Calculate the maximum mass of carbon dioxide given off when 20.0 g of small lumps of calcium carbonate react with 40 cm3 of hydrochloric acid, concentration 2.0 mol / dm3. CaCO3+ 2HCl  CaCl 2+ H2O+ CO2number of moles of HCl used = mass of carbon dioxide = g
6. Chemical reactions  →  6.2. Rate of reaction
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5
For Examiner’s Use The alkenes are unsaturated hydrocarbons. They form a homologous series, the members of which have the same chemical properties. They undergo addition reactions and are easily oxidised. The following hydrocarbons are isomers. CH3 CH3 CH2 CH CH CH3 CH2 CH2 CH2 CH Explain why these two hydrocarbons are isomers. Give the structural formula of another hydrocarbon which is isomeric with the above. Give the structural formula and name of each of the products of the following addition reactions. ethene and bromine structural formula of product name of product propene and hydrogen structural formula of product name of product but-1-ene and water structural formula of product name of product For Examiner’s Use Alkenes can be oxidised to carboxylic acids. For example, propene, CH3 – CH = CH2, would produce ethanoic acid, CH3 – COOH, and methanoic acid, H – COOH. Deduce the formulae of the alkenes which would form the following carboxylic acids when oxidised. ethanoic acid and propanoic acid only ethanoic acid Describe the colour change you would observe when an alkene is oxidised with acidifi ed potassium manganate(. Alkenes polymerise to form addition polymers. Draw the structural formula of poly, include at least two monomer units. The structural formula of the monomer, cyanoethene, is given below. C C H CN H H
11. Organic chemistry  →  11.5. Alkenes
11. Organic chemistry  →  11.8. Polymers
11. Organic chemistry  →  11.2. Naming organic compounds
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6
For Examiner’s Use Lead is an excellent roofi ng material. It is malleable and resistant to corrosion. Lead rapidly becomes coated with basic lead carbonate which protects it from further corrosion. Lead has a typical metallic structure which is a lattice of lead ions surrounded by a ‘sea’ of mobile electrons. This structure is held together by attractive forces called a metallic bond. Explain why there are attractive forces in a metallic structure. Explain why a metal, such as lead, is malleable. Basic lead(carbonate is heated in the apparatus shown below. Water and carbon dioxide are produced. soda lime, carbon dioxide reacts here basic lead carbonate heat U-tube filled with silica gel to absorb water Silica gel absorbs water. Silica gel often contains anhydrous cobalt(chloride. When this absorbs water it changes from blue to pink. Suggest a reason. Soda lime is a mixture of sodium hydroxide and calcium oxide. Why do these two substances react with carbon dioxide? Name two substances formed when soda lime reacts with carbon dioxide. For Examiner’s Use Basic lead(carbonate has a formula of the type xPbCO3.yPb(OH)2 where x and y are whole numbers. Determine x and y from the following information. PbCO3  PbO + CO2 Pb(OH)2  PbO + H2O When heated, the basic lead(carbonate gave 2.112 g of carbon dioxide and 0.432 g of water. Mass of one mole of CO2 = 44 g Mass of one mole of H2O = 18 g Number of moles of CO2 formed = Number of moles of H2O formed = x = and y = Formula of basic lead(carbonate is
4. Electrochemistry  →  4.1. Electrolysis
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
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7
For Examiner’s Use The following are two examples of substitution reactions. Only the reaction involving chlorine is a photochemical reaction. CH4 + Cl 2  CH3Cl + HCl CH4 + Br2  CH3Br + HBr Explain the phrase substitution reaction. How do photochemical reactions differ from other reactions? Bond forming is exothermic, bond breaking is endothermic. Explain the difference between an exothermic reaction and an endothermic reaction. For Examiner’s Use Use the bond energies to show that the following reaction is exothermic. Bond energy is the amount of energy (kJ / mol) which must be supplied to break one mole of the bond. H C H H H H C H H Cl Cl Cl H Cl + + → Bond energies in kJ / mol Cl –Cl +242 C–Cl +338 C–H +412 H–Cl +431 bonds broken energy in kJ / mol total energy = bonds formed energy in kJ / mol total energy =
5. Chemical energetics  →  5.1. Exothermic and endothermic reactions
11. Organic chemistry  →  11.4. Alkanes
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