0620_s13_qp_31
A paper of Chemistry, 0620
Questions:
8
Year:
2013
Paper:
3
Variant:
1
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An element, M, has the electron distribution 2 + 8 + 18 + 3. Which group in the Periodic Table is element M likely to be in? Predict whether element M is a poor or a good conductor of electricity. Give a reason for your answer. Binary compounds contain two atoms per molecule, for example HCl. Identify an element which could form a binary compound with element M. Predict the formula of the sulfate of M. The formula of the sulfate ion is SO4 2–. For Examiner’s Use The hydroxide of M is a white powder which is insoluble in water. Describe how you could show that this hydroxide is amphoteric.
8. The Periodic Table  →  8.1. Arrangement of elements
2. Atoms, elements and compounds  →  2.2. Atomic structure and the Periodic Table
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A small piece of marble, CaCO3, was added to 5.0 cm3 of hydrochloric acid, concentration 1.0 mol / dm3, at 25 °C. The time taken for the reaction to stop was measured. The experiment was repeated using 5.0 cm3 of different solutions of acids. The acid was in excess in all of the experiments. Typical results are given in the table. experiment temperature / °C acid solution time / min hydrochloric acid 1.0 mol / dm3 hydrochloric acid 0.5 mol / dm3 ethanoic acid 1.0 mol / dm3 hydrochloric acid 1.0 mol / dm3 Explain why it is important that the pieces of marble are the same size and the same shape. How would you know when the reaction had stopped? The equation for the reaction in experiment 1 is: CaCO3+ 2HCl → CaCl 2+ CO2+ H2OComplete the following ionic equation. CaCO3+ 2H+→ + + For Examiner’s Use Explain why the reaction in experiment 1 is faster than the reaction in experiment 2. The acids used for experiment 1 and experiment 3 have the same concentration. Explain why experiment 3 is slower than experiment 1. Explain in terms of collisions between reacting particles why experiment 4 is slower than experiment 1.
6. Chemical reactions  →  6.2. Rate of reaction
9. Metals  →  9.4. Reactivity series
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The structural formula of cyclohexane is drawn below. CH2 CH2 CH2 H2C H2C CH2 The name gives information about the structure of the compound. Hex because there are six carbon atoms and cyclo because they are joined in a ring. What information about the structure of this compound is given by the ending ane? What are the molecular and empirical formulae of cyclohexane? molecular formula empirical formula For Examiner’s Use Draw the structural formula of cyclobutane. Deduce the molecular formula of hexene. Explain why cyclohexane and the alkene, hexene, are isomers. Describe a test which would distinguish between cyclohexane and the unsaturated hydrocarbon hexene. test result of test with cyclohexane result of test with hexene
3. Stoichiometry  →  3.1. Formulae
11. Organic chemistry  →  11.1. Formulae, functional groups and terminology
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For Examiner’s Use The reactivity series shows the metals in order of reactivity. The reactivity series can be established using displacement reactions. A piece of zinc is added to aqueous lead nitrate. The zinc becomes coated with a black deposit of lead. Zn + Pb2+ → Zn2+ + Pb Zinc is more reactive than lead. The reactivity series can be written as a list of ionic equations. → + most reactive metal : the best reductant (reducing agent) Zn → Zn2+ + 2e– Fe → Fe2+ + 2e– Pb → Pb2+ + 2e– Cu → Cu2+ + 2e– Ag → Ag+ + e– In the space at the top of the list, write an ionic equation for a metal which is more reactive than zinc. Write an ionic equation for the reaction between aqueous silver(nitrate and zinc. Explain why the positive ions are likely to be oxidants (oxidising agents). Deduce which ion is the best oxidant (oxidising agent). Which ionin the list can oxidise lead metal? For Examiner’s Use A reactivity series can also be established by measuring the voltage of simple cells. The diagram shows a simple cell. V voltmeter copper electrode sulfuric acid cadmium electrode Results from cells using the metals tin, cadmium, zinc and copper are given in the table below. cell electrode 1 positive electrode electrode 2 negative electrode voltage / volts copper cadmium 0.74 copper tin 0.48 copper zinc 1.10 Write the four metals in order of increasing reactivity and explain how you used the data in the table to determine this order.
9. Metals  →  9.4. Reactivity series
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Ammonia is a compound which only contains the elements nitrogen and hydrogen. It is a weak base. Defi ne the term base. Given aqueous solutions of ammonia and sodium hydroxide, both having a concentration of 0.1 mol / dm3, how could you show that ammonia is the weaker base? For Examiner’s Use Ammonia is manufactured by the Haber Process. The economics of this process require that as much ammonia as possible is made as quickly as possible. Explain how this can be done using the following information. The conditions for the following reversible reaction are: ● 450 °C ● 200 atmospheres pressure ● iron catalyst N2+ 3H22NH3the reaction is exothermic Another compound which contains only nitrogen and hydrogen is hydrazine, N2H4. Complete the equation for the preparation of hydrazine from ammonia. NH3 + NaCl O → N2H4 + + H2O The structural formula of hydrazine is given below. N N H H H H Draw a diagram showing the arrangement of the valency electrons in one molecule of the covalent compound hydrazine. Use x to represent an electron from a nitrogen atom. Use o to represent an electron from a hydrogen atom. For Examiner’s Use Hydrazine is a weak base and it removes dissolved oxygen from water. It is added to water in steel boilers to prevent rusting. One way it reduces the rate of rusting is by changing the pH of water. What effect would hydrazine have on the pH of water? Give a reason, other than pH, why hydrazine reduces the rate of rusting.
6. Chemical reactions  →  6.3. Reversible reactions and equilibrium
7. Acids, bases and salts  →  7.1. The characteristic properties of acids and bases
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The hydroxides of the Group I metals are soluble in water. Most other metal hydroxides are insoluble in water. Crystals of lithium chloride can be prepared from lithium hydroxide by titration. conical flask burette filled with hydrochloric acid of concentration 2.20 mol / dm3 25.0 cm3 of aqueous lithium hydroxide and indicator 25.0 cm3 of aqueous lithium hydroxide is pipetted into the conical fl ask. A few drops of an indicator are added. Dilute hydrochloric acid is added slowly to the alkali until the indicator just changes colour. The volume of acid needed to neutralise the lithium hydroxide is noted. A neutral solution of lithium chloride, which still contains the indicator, is left. Describe how you could obtain a neutral solution of lithium chloride which does not contain an indicator. For Examiner’s Use You cannot prepare a neutral solution of magnesium chloride by the same method. Describe how you could prepare a neutral solution of magnesium chloride. The concentration of the hydrochloric acid was 2.20 mol / dm3. The volume of acid needed to neutralise the 25.0 cm3 of lithium hydroxide was 20.0 cm3. Calculate the concentration of the aqueous lithium hydroxide. LiOH + HCl → LiCl + H2O Lithium chloride forms three hydrates. They are LiCl.H2O, LiCl.2H2O and LiCl.3H2O. Which one of these three hydrates contains 45.9 % of water? Show how you arrived at your answer.
12. Experimental techniques and chemical analysis  →  12.5. Identification of ions and gases
9. Metals  →  9.4. Reactivity series
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There are three types of giant structure - ionic, metallic and giant covalent. In an ionic compound, the ions are held in a lattice by strong forces. Explain the term lattice. Explain how the ions are held together by strong forces. For Examiner’s Use Describe the bonding in a typical metal. The electrical conductivities of the three types of giant structure are given in the following table. type of structure conductivity of solid conductivity of liquid ionic poor good metallic good good giant covalent poor poor Explain the differences in electrical conductivity between the three types of giant structure and the difference, if any, between the solid and liquid states of the same structure.
2. Atoms, elements and compounds  →  2.5. Simple molecules and covalent bonds
2. Atoms, elements and compounds  →  2.4. Ions and ionic bonds
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