9701_w12_qp_42
A paper of Chemistry, 9701
Questions:
8
Year:
2012
Paper:
4
Variant:
2
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1
Write down what you would see, and write equations for the reactions that occur, when silicon(chloride and phosphorus(chloride are separately mixed with water. silicon(chloride phosphorus(chloride Iron(chloride, FeCl 3, is used to dissolve unwanted copper from printed circuit boards (PCBs) by the following reaction. 2FeCl 3+ Cu→ 2FeCl 2+ CuCl 2A solution in which [Fe3+] was originally equal to 1.50 mol dm–3 was re-used several times to dissolve copper from the PCBs, and was then titrated as follows. A 2.50 cm3 sample of the partially-used-up solution was acidifi ed and titrated with 0.0200 mol dm–3 KMnO4. This oxidised any FeCl 2 in the solution back to FeCl 3. It was found that 15.0 cm3 of KMnO4was required to reach the end point. Construct an ionic equation for the reaction between Fe2+ and MnO4 – in acid solution. State here the Fe2+ : MnO4 – ratio from your equation in . Calculate the number of moles of MnO4 – used in the titration. Calculate the number of moles of Fe2+ in 2.50 cm3 of the partially-used-up solution. For Examiner’s Use Calculate the [Fe2+] in the partially-used-up solution. Calculate the mass of copper that could still be dissolved by 100 cm3 of the partially-used-up solution. mass of copper = g When SiCl 4 vapour is passed over Si at red heat, Si2Cl 6 is formed. Si2Cl 6 contains a Si-Si bond. The reaction of Si2Cl 6 and Cl 2 re-forms SiCl 4. Si2Cl 6+ Cl 2→ 2SiCl 4Use bond energy data from the Data Booklet to calculate ∆H o for this reaction. ∆H o = kJ mol–1 Calcium forms three calcium silicides, Ca2Si, CaSi and CaSi2. The fi rst of these reacts with water as follows. Ca2Si + H2O → Ca(OH)2 + SiO2 + H2 Balance this equation. You may fi nd the use of oxidation numbers helpful. During this reaction, state which elementhave been oxidised, which elementhave been reduced.
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
11. Group 17  →  11.4. The reactions of chlorine
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For Examiner’s Use The diagram below shows an incomplete experimental set-up needed to measure the Ecell of a cell composed of the standard Cu2+/Cu electrode and an Ag+/Ag electrode. copper electrode solution A electrode B saturated solution of AgCl solid AgCl State the chemical composition of solution A, electrode B. Complete the diagram to show the whole experimental set-up. The above cell is not under standard conditions, because the [Ag+] in a saturated solution of AgCl is much less than 1.0 mol dm–3. The Eelectrode is related to [Ag+] by the following equation. equation 1 Eelectrode = E electrode + 0.06 log[Ag+] Use the Data Booklet to calculate the E cell if the cell was operating under standard conditions. E cell = V In the above experiment, the Ecell was measured at +0.17V. Calculate the value of Eelectrode for the Ag+/Ag electrode in this experiment. Use equation 1 to calculate [Ag+] in the saturated solution. [Ag+] = mol dm–3 o o o For Examiner’s Use Write an expression for Ksp of silver sulfate, Ag2SO4, including units. Ksp = units Using a similar experimental set-up to that illustrated opposite, it is found that [Ag+] in a saturated solution of Ag2SO4 is 1.6 × 10–2 mol dm–3. Calculate the value of Ksp of silver sulfate. Ksp = Describe how the colours of the silver halides, and their relative solubilities in NH3, can be used to distinguish between solutions of the halide ions Cl –, Br – and I –. Describe and explain the trend in the solubilities of the sulfates of the elements in Group II.
11. Group 17  →  11.3. Some reactions of the halide ions
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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For Examiner’s Use Catalysts can be described as homogeneous or heterogeneous. What is meant by the terms homogeneous and heterogeneous? By using iron and its compounds as examples, outline the different modes of action of homogeneous and heterogeneous catalysis. Choose one example of each type, and for each example you should ● state what the catalyst is, and whether it is acting as a homogeneous or a heterogeneous catalyst, ● write a balanced equation for the reaction, ● outline how the catalyst you have chosen works to decrease the activation energy. For Examiner’s Use The reaction between SO2, NO2 and O2 occurs in two steps. NO2 + SO2 → NO + SO3 ∆H 1 = –88 kJ mol–1 NO + 2 1O2 → NO2 ∆H 2 = –57 kJ mol–1 The activation energy of the fi rst reaction, Ea1, is higher than that of the second reaction, Ea2. Use the axes below to construct a fully-labelled reaction pathway diagram for this reaction, labelling Ea1, Ea2, ∆H 1 and ∆H 2. energy extent of reaction NO2 + SO2 o o o o
8. Reaction kinetics  →  8.3. Homogeneous and heterogeneous catalysts
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
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For Examiner’s Use The compound responsible for the hot taste of chilli peppers is capsaicin. Its molecular structure can be deduced by the following reaction scheme. capsaicin, C18H27NO3 C, C10H18O2 D, C6H10O4 E, C4H8O2 + + boil with H3O+ reaction 5 reaction 3 reaction 4 heat with KCN heat with concentrated acidified KMnO4 NH2 OCH3 HO F, C6H8N2 Br(CH2)4Br (CH3)2CHCH2OH reaction 1 reaction 2 Compounds C, D and E all react with Na2CO3. For Examiner’s Use Answer the following questions. Suggest reagents and conditions for reaction 3. What type of reaction is reaction 4? Suggest reagents and conditions for reaction 5. Name the functional group in C that has reacted with hot concentrated acidifi ed KMnO4. Suggest the name of the functional group in capsaicin that has reacted in reaction 1. Work out structures for compounds C–F and capsaicin, and draw their structural formulae in the boxes opposite.
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
16. Hydroxy compounds  →  16.1. Alcohols
14. Hydrocarbons  →  14.1. Alkanes
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For Examiner’s Use Compound G is a naturally occurring aromatic compound that is present in raspberries. HO O compound G Identify the functional groups present in compound G. Complete the following table with information about the reactions of the three stated reagents with compound G. reagent observation structure of organic product type of reaction sodium metal aqueous bromine aqueous alkaline iodine For Examiner’s Use The dye H can be made from compound G by the route shown below. J K step 1 step 2 compound G dye H HO N SO3H N O Draw the structures of the amine J and the intermediate K in the boxes above. Suggest reagents and conditions for step 1, step 2. Suggest a reaction scheme by which compound G and propanoic acid could be converted into compound L. compound L O O O
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
21. Organic synthesis  →  21.1. Organic synthesis
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Proteins are complex molecules made up from long chains that are folded to give a three-dimensional structure. Study the table which describes aspects of bonding in proteins. For each description of a bonding type, indicate whether it contributes to the primary, secondary or tertiary structure of a protein. bonding type structure involved disulfi de bonds between parts of the chain hydrogen bonds in a β-pleated sheet ionic bonds between parts of the chain peptide links between amino acids Explain, with the use of diagrams as appropriate, the difference between competitive and non-competitive inhibition of enzymes. For Examiner’s Use The diagram shows one strand of DNA. Draw a matching strand showing clearly, with labels, the bonds holding the two strands together. Name the bases in your strand, indicating clearly which base bonds to each base in the strand shown. phosphate T phosphate phosphate G sugar sugar names of bases
3. Chemical bonding  →  3.4. Covalent bonding and coordinate (dative covalent) bonding
4. States of matter  →  4.2. Bonding and structure
13. An introduction to AS Level organic chemistry  →  13.3. Shapes of organic molecules; σ and π bonds
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For Examiner’s Use DNA fi ngerprinting has become an important analytical technique, largely due to its use in ‘screening’ crime suspects. It also has a range of applications in modern analysis including determining family links, medicine and archaeology. DNA fi ngerprinting uses an analytical technique you have studied. What is the name of that technique? In order to carry out DNA fi ngerprinting, the DNA must fi rst be broken down into shorter lengths of polynucleotides. How is this accomplished? What part of the DNA fragments enables them to move in an electric fi eld? The DNA fi ngerprints shown were obtained from a crime scene. DNA samples were recovered from two rooms in the house where the crime took place. The victim’s DNA and that of two possible suspects were included in the analysis. victim suspect 1 suspect 2 crime scene 1 crime scene 2 start point Indicate with an X on the diagram, which lines from suspect 1 and from suspect 2 cannot distinguish which of them was present in the house. Based on this evidence one suspect was arrested. Which suspect would you expect this to be? Explain your reasoning. For Examiner’s Use A sample of a liquid, P, was found at the scene of the crime and was analysed using mass spectrometry and NMR spectroscopy. The mass spectrum has M and M+1 peaks in the ratio of 5.1: 0.22 with the M peak at m/e = 88. The NMR spectrum is shown δ / ppm Use the data to suggest a structure for P, explaining your answer. structure of P
22. Analytical techniques  →  22.2. Mass spectrometry
4. States of matter  →  4.2. Bonding and structure
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For Examiner’s Use The increasing awareness of the diminishing supply of crude oil has resulted in a number of initiatives to replace oil-based polymers with those derived from natural products. One such polymer, ‘polylactide’ or PLA, is produced from corn starch and has a range of applications. The raw material for the polymer, lactic acid (2-hydroxypropanoic acid), is formed by the fermentation of corn starch using enzymes from bacteria. Calcium hydroxide is added to the fermentation tanks to prevent the production of lactic acid from slowing down. Why might high acidity reduce the effectiveness of the enzymes? The structure of lactic acid is shown. H C CO2H CH3 HO What type of reaction takes place in this polymerisation? Lactic acid exists in two stereoisomeric forms. Draw the other form in the box. For Examiner’s Use One of the reasons PLA has attracted so much attention is that it is biodegradeable. This does, however, restrict some potential uses. The simple polymer has a melting point of around 175 °C, but softens between 60-80 °C. However, its thermoplastic properties enable it to have a range of uses in fi bres and in food packaging. Explain why PLA would not be a suitable packaging material for foods pickled in vinegar. PLA containers are not used for hot drinks. Suggest why. Lactic acid can also be co-polymerised with glycolic acid. HO C H H C O OH glycolic acid Draw a section of the co-polymer showing one repeat unit. Suggest what typeof bonding will occur between chains of this co-polymer, indicating the groups involved. Suggest one property in which the co-polymer differs from PLA.
20. Polymerisation  →  20.1. Addition polymerisation
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
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