9701_s10_qp_41
A paper of Chemistry, 9701
Questions:
10
Year:
2010
Paper:
4
Variant:
1
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Phosphorus and sulfur are two non-metallic elements on the right hand side of the Periodic Table. For each of these elements describe the observations you would make when it burns in air, and write a balanced equation for the reaction. phosphorus observation equation sulfur observation equation White phosphorus, P4, is produced commercially by heating calcium phosphate(rock with a mixture of silica, SiO2, and coke in an electric furnace at 1400 °C. Calcium silicate, CaSiO3, and carbon monoxide are the other products. Balance the following equation which represents the overall process. ___ Ca3(PO4)2 + ___ SiO2 + ___ C ___ P4 + ___ CaSiO3 + ___ CO When heated to 400 °C in the absence of air, white phosphorus is changed into the red form of the element. The following table lists some of the properties of the two forms, which are known as allotropes. allotrope electrical conductivity melting point / °C solubility in water solubility in benzene white none insoluble soluble red none insoluble insoluble Suggest the type of structure and bonding in each allotrope. allotrope type of structure type of bonding white red For Examiner’s Use In both allotropes, phosphorus has a valency of 3. Suggest by means of diagrams how the phosphorus atoms might be joined together in each allotrope. white phosphorus red phosphorus
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
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For Examiner’s Use Describe three characteristic chemical properties of transition elements that are not shown by Group II elements. When NH3is added to a green solution containing Ni2+ions, a grey-green precipitate is formed. This precipitate dissolves in an excess of NH3to give a blue- violet solution. Suggest an explanation for these observations, showing your reasoning and including equations for the reactions you describe. Dimethylglyoxime, DMG, is a useful reagent for the quantitative estimation of nickel. It forms an insoluble salt with nickel ions according to the following equation. Ni2++ C4H8N2O2 NiC4H6N2O2+ 2H+DMG Ni-DMG A small coin of mass 3.40 g was dissolved in nitric acid and an excess of DMG was added. The precipitated Ni-DMG was filtered off, washed and dried. Its mass was 4.00 g. Calculate the % of nickel in the coin. percentage of nickel = %
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
11. Group 17  →  11.3. Some reactions of the halide ions
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For Examiner’s Use Describe how the behaviour of the oxides of tin and lead in their +4 oxidation states differ on heating. Explain the following by using data from the Data Booklet where appropriate, and writing equations for all reactions. A sample of liquid PbCl4 is placed in a flask and the flask is gently warmed. A gas is evolved and a white solid is produced. When the gas is bubbled through KI, purple fumes are produced. Repeating the same experiment using liquid SnCl4 instead of PbCl4 results in no evolution of gas, and no reaction with KI. The molecule dichlorocarbene, CCl2, can be produced under certain conditions. It is highly unstable, reacting with water to produce carbon monoxide and a strongly acidic solution. Suggest the electron arrangement in CCl2 and draw a dot-and-cross diagram showing this. Predict the shape of the molecule. Construct an equation for the reaction of CCl2 with water.
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
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For Examiner’s Use Ethanolamine and phenylamine are two organic bases that are industrially important. Ethanolamine is a useful solvent with basic properties, whilst phenylamine is an important starting material in the manufacture of dyes and pharmaceuticals. The following table lists some of their properties, together with those of propylamine. compound formula Mr boiling point/ °C solubility in water propylamine CH3CH2CH2NH2 fairly soluble ethanolamine HOCH2CH2NH2 very soluble phenylamine NH2 sparingly soluble Suggest why the boiling point of ethanolamine is much higher than that of propylamine. Draw a diagram to illustrate your answer. Describe and explain the relative basicities of propylamine and phenylamine. Write an equation showing ethanolamine acting as a Brønsted-Lowry base. For Examiner’s Use Propylamine can be synthesised from bromoethane by the following route. CH3CH2Br CH3CH2CH2NH2 step 1 X step 2 Draw the structure of the intermediate compound X in the box above. Suggest reagents and conditions for step 1 step 2 Apart from their relative basicities, ethanolamine and phenylamine differ in many of their reactions. For each of these two compounds, describe one test that would give a positive result with the stated compound, but a negative result with the other. ethanolamine test observation phenylamine test observation
15. Halogen compounds  →  15.1. Halogenoalkanes
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For Examiner’s Use Although standard electrode potentials are measured for solutions where the concentrations of ions are 1.0 mol dm–3, cells used as sources of battery power tend to operate with more concentrated solutions. This question concerns the electrode reactions involved in the hydrogen-oxygen fuel cell and the lead-acid car battery. In the hydrogen-oxygen fuel cell, H2and O2are fed onto two inert electrodes dipping into NaOH. V hydrogen oxygen NaOHThe following reactions take place. left hand electrode : H2+ 2OH–2H2O+ 2e– right hand electrode : O2+ 2H2O+ 4e– 4OH–Use the Data Booklet to calculate E o–– cell for this reaction. Construct an equation for the overall reaction. By using one of the phrases more positive, more negative or no change, deduce the effect of increasing [OH–] on the electrode potential of • the left hand electrode • the right hand electrode Hence deduce whether the overall Ecell is likely to increase, decrease or remain the same, when [OH–] increases. Explain your answer. Suggest one other reason why a high [NaOH] is used in the fuel cell. For Examiner’s Use In the cells of a lead-acid car battery the following reactions take place. cathode: PbPb2++ 2e– anode: PbO2+ 4H++ 2e– Pb2++ 2H2OUse the Data Booklet to calculate E o–– cell for this reaction. Construct an equation for the overall reaction. The electrolyte in a lead-acid cell is H2SO4. Most of the Pb2+ions that are produced at the electrodes are precipitated as the highly insoluble PbSO4. Construct an equation for the overall cell reaction in the presence of H2SO4. By considering the effect of decreasing [Pb2+] on the electrode potentials of the cathode and the anode, deduce the effect of the presence of H2SO4in the electrolyte on the overall Ecell. State whether the Ecell will increase, decrease or remain the same. Overall Ecell will . Explain your answer.
14. Hydrocarbons  →  14.2. Alkenes
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
8. Reaction kinetics  →  8.3. Homogeneous and heterogeneous catalysts
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For Examiner’s Use Acyl chlorides are useful intermediates in organic syntheses. State a suitable reagent for converting carboxylic acids into acyl chlorides. Construct an equation for the reaction between ethanoic acid, CH3CO2H, and the reagent you have stated in . In the boxes provided draw the structures of the compounds formed when benzoyl chloride undergoes the following reactions. C2H5OH COCl I II A NH3 B Name the functional group in • compound A • compound B . What type of reaction is reaction II? For Examiner’s Use Suggest suitable acyl chlorides to use in the following reaction. Draw their structures in the boxes provided. + H2N NH2 NH HN O O OH OH O O C E O O O n + D F Compound E dissolves in, but does not react with, cold water. Suggest the major type of intermolecular interaction that occurs between E and water. A solution of the diamine H2NCH2CH2NH2 in water has pH = 11 but a solution of E in water has pH = 7. Suggest why this is the case. What type of polymer is compound F?
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
14. Hydrocarbons  →  14.2. Alkenes
21. Organic synthesis  →  21.1. Organic synthesis
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The molecule that contains the genetic information for an individual organism is called deoxyribonucleic acid, DNA. The diagram shows part of a DNA molecule. Study the diagram and identify the blocks labelled J, K, L and M as accurately as you can. J cytosine K adenine M L block letter identity J K L M The DNA molecule is formed from two polymer strands. What stops these strands from separating from each other? For Examiner’s Use List three differences between the structures of DNA and RNA. 1. 2. 3. Outline the different roles of mRNA and tRNA in the processes of transcription and translation. mRNA tRNA
13. An introduction to AS Level organic chemistry  →  13.4. Isomerism: structural isomerism and stereoisomerism
20. Polymerisation  →  20.1. Addition polymerisation
21. Organic synthesis  →  21.1. Organic synthesis
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For Examiner’s Use A range of modern analytical techniques has made the identification of molecules, and atoms in compounds, much more rapid than traditional laboratory analysis. One instrumental technique is NMR spectroscopy, which uses the fact that under certain conditions protons can exist in two different energy states. Explain how these different energy states arise. When methanol, CH3OH, is examined using NMR spectroscopy, it absorbs at two different frequencies. Explain why, and predict the relative areas of the two peaks. The NMR spectrum below is that of one of three possible isomers of molecular formula C3H6O2. chemical shift, δ / ppm A B For Examiner’s Use The compound could be propanoic acid, methyl ethanoate or ethyl methanoate. In the boxes provided, draw the structures of the three compounds. propanoic acid methyl ethanoate ethyl methanoate Explain which compound produced the spectrum shown, indicating which protons are responsible for each of the peaks A and B. The NMR spectrum of another of the compounds has a peak at δ11.0. State which compound this would be, and identify the protonresponsible for this peak. compound proton X-ray crystallography is a technique used to identify the relative positions of atoms in a crystal of a compound. What further information about organic macromolecules can be deduced by the use of X-ray crystallography? Which atoms cannot be located by X-ray crystallography?
22. Analytical techniques  →  22.2. Mass spectrometry
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
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For Examiner’s Use 10 The nature and variety of drugs that are available to treat diseases or life-threatening conditions has never been greater. At the same time, we are much better able to deliver drugs to their targets in the body. Some drugs have to be given by injection, rather than by mouth. Name a functional group in a drug molecule that might be broken down by the acid in the stomach. The anti-cancer drug Taxol could be broken down if taken by mouth. O O O O O O O O O O OH O NH HO OH H Taxol Circle two bonds, each in a different functional group, that could be hydrolysed in the digestive system. For Examiner’s Use One way of protecting drug molecules that are taken by mouth is to enclose them in liposomes. These are artificially created spheres made from phospholipids which have an ionic phosphate ‘head’ and two hydrocarbon ‘tails’. B A C phospholipid State in which area of the liposome, A, B or C, each of the following types of drug would be carried. a hydrophilic drug a hydrophobic drug For the remaining position, A, B or C, explain why this would not be a suitable area for carrying a drug. One way of carrying drugs in the bloodstream is to attach them by a chemical bond to a polymer. One such polymer is polyethylene glycol or PEG. HO – (CH2 – CH2 – O)n – H Where would a drug be attached to a molecule of PEG? Suggest why a liposome can carry more drug molecules than a molecule of PEG. For Examiner’s Use Better-targeted delivery of drugs allows smaller amounts to be used, which brings significant advantages. Suggest two advantages of using smaller drug doses.
20. Polymerisation  →  20.1. Addition polymerisation
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
14. Hydrocarbons  →  14.2. Alkenes
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