9701_s21_qp_43
A paper of Chemistry, 9701
Questions:
9
Year:
2021
Paper:
4
Variant:
3
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1
The carbonates and hydroxides of Group2 elements show similar trends in thermal stability. Suggest and explain the variation in the trend in the thermal stability of the Group2 hydroxides. Calciumhydroxide is slightly soluble in water. Write an equation to show the dissociation of calciumhydroxide, Ca(OH)2, in aqueous solution. Include state symbols. ��������������������������������������������������������������� Calculate the solubility, in mol dm–3, of Ca(OH)2. [Ksp: Ca(OH)2, 5.02 × 10–6 mol3 dm–9]  solubility = mol dm–3 Suggest how the solubility of Ca(OH)2 in aqueous NaOH compares to its solubility in water. Explain your reasoning. 
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
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Explain why chromium complexes are coloured. Four different compounds can be obtained when anhydrous chromium(chloride reacts with water under various conditions. When samples of each compound are reacted separately with aqueous silvernitrate, different amounts of silverchloride are precipitated. The precipitation leaves the complex ions P, Q, R and S in solution. formula of compound moles of AgCl precipitated per mole of complex ion complex ion property of complex ion CrCl 3(H2O)6 P non-polar CrCl 3(H2O)5 Q polar CrCl 3(H2O)4 R polar CrCl 3(H2O)4 S non-polar Draw three-dimensional diagrams for the structures of complex ions P, Q, R and S. Include the charges for each complex ion. P Cr Q Cr R Cr S Cr  Suggest why complex ion S is non-polar. The structure of picolinicacid is shown. picolinic acid CO2H N The conjugate base of picolinicacid is a bidentate ligand, Z. Define the term bidentate ligand. Draw the structure of Z.  Z reacts with aqueous chromium(ions, [Cr(H2O)6]3+, in a 3 : 1 ratio to form a new neutral complex. State the coordination number and the geometry of the chromium(centre in the complex. coordination number geometry ����������������������������������������� (NH4)2Cr2O7 decomposes readily on heating to form Cr2O3, steam and an inert colourless gas. Deduce the oxidation numbers of chromium in (NH4)2Cr2O7 and in Cr2O3. (NH4)2Cr2O7 Cr2O3 ��������������������������������������������������� Construct an equation for the thermal decomposition of (NH4)2Cr2O7. 
11. Group 17  →  11.3. Some reactions of the halide ions
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
11. Group 17  →  11.1. Physical properties of the Group 17 elements
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Define the term transition element. State how the melting point and density of iron compare to those of calcium. Define the term standard cell potential, . Draw a fully labelled diagram of the apparatus that can be used to measure the cell potential of a cell composed of a Cu(/Cu electrode and an Fe(/Fe(electrode. Include all necessary reactants.  The reaction between S2O8 2–and I –is catalysed by adding a few drops of Fe3+. Use equations to show the catalytic role of Fe3+ in this reaction.  Fe3+can oxidise I –, whereas [Fe(CN)6]3–cannot oxidise I –. Use E o values to explain these observations. When aqueous solutions of S2O8 2– and tartrate ions are mixed the reaction proceeds very slowly. However, this reaction proceeds quickly in the presence of an Fe3+catalyst. The overall equation for this reaction is shown. tartrate ions + 3S2O8 2– + 2H2O 2CO2 + 2HCO2 – + 6H+ + 6SO4 2– OH OH CO2 – –O2C Suggest why this reaction is slow without the Fe3+ catalyst. Use the overall equation to deduce the half-equation for the oxidation of tartrate ions, C4H4O6 2–, to carbondioxide, CO2, and methanoate ions, HCO2 –. C4H4O6 2– +  Complete the following table to show the structures of the organic products formed when tartaric acid reacts separately with each reagent. Identify each type of reaction. tartaric acid OH OH CO2H HO2C reagent structure of organic product type of reaction an excess of LiAl H4 an excess of CH3COCl  Tartaric acid reacts with the amine 1-phenylethylamine, C6H5CH(NH2)CH3, to form an ionicsalt. Draw the structure of the salt formed in this reaction. Include the charges on the ions.  
11. Group 17  →  11.3. Some reactions of the halide ions
14. Hydrocarbons  →  14.2. Alkenes
8. Reaction kinetics  →  8.3. Homogeneous and heterogeneous catalysts
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Samples of [Cu(H2O)6]2+ are reacted separately with an excess of aqueous sodiumhydroxide or with an excess of aqueous ammonia. Give the following information about these reactions. reaction 1: [Cu(H2O)6]2+ with an excess of aqueous of sodium hydroxide colour and state of the copper-containing species ionic equation type of reaction  reaction 2: [Cu(H2O)6]2+ with an excess of aqueous ammonia colour and state of the copper-containing species ionic equation type of reaction  Copper(oxide is added to hot dilute sulfuricacid. A blue solution, X, and a red-brown solid, Y, form. Suggest the identities of X and Y. Name the type of reaction. X Y type of reaction  
11. Group 17  →  11.4. The reactions of chlorine
11. Group 17  →  11.3. Some reactions of the halide ions
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Dinitrogenpentoxide, N2O5, is dissolved in an inert solvent and the rate of decomposition of N2O5 is investigated. This reaction produces nitrogendioxide, which remains in solution, and oxygen gas. N2O5→ 2NO2+ 1 2O2Suggest what measurements could be used to follow the rate of this reaction from the given information. In a separate experiment, the rate of the decomposition of N2O5is investigated. N2O5→ 2NO2+ 1 2O2The graph shows the results obtained. 0.30 0.25 0.20 0.15 0.10 0.05 time / s [N2O5] / mol dm–3 The reaction is first order with respect to N2O5. This can be confirmed from the graph using half‑lives. Explain the term half-life of a reaction. Determine the half-life of this reaction. Show your working on the graph.  half-life = s Suggest the effect on the half-life of this reaction if the initial concentration of N2O5 is halved. Use the graph in 5to determine the rate of reaction at 200 s. Show your working.  rate =  units =  The rate equation for this reaction is shown. rate = k [N2O5] Use your answer to to calculate the value of the rate constant, k, for this reaction and state its units.  k = units Nitrogendioxide reacts with ozone, O3, as shown. 2NO2 + O3 → N2O5 + O2 The rate equation for this reaction is rate = k [NO2][O3]. Suggest a possible two-step mechanism for this reaction. 
8. Reaction kinetics  →  8.1. Rate of reaction
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Compare and explain the relative acidities of butanoicacid, ethanol, ethanoicacid and water. > > > most acidic least acidic Three carboxylic acids, methanoic acid, HCO2H, ethanedioic acid, HO2CCO2H, and butanedioicacid, HO2CCH2CH2CO2H, are compared. Two tests were carried out on separate samples of each organic acid, as shown. The following results were obtained.  = observed change  = no observed reaction test reagents and conditions HCO2H HO2CCO2H HO2CCH2CH2CO2H observed change       Complete the table with the reagents and conditions and the observed change for a positive test. Assume these organic acids all have a similar acid strength. Each compound, HCO2H, HO2CCO2H and HO2CCH2CH2CO2H, is dissolved seperately in CDCl 3. Proton (1H) NMR and carbon‑13 (13C) NMR spectra are then obtained. Complete the table. compound number of peaks in proton NMR number of peaks in carbon-13 NMR HCO2H HO2CCO2H HO2CCH2CH2CO2H  The proton NMR spectrum of HCO2H in D2O is obtained. Describe and explain the difference observed between this spectrum and the proton NMR spectrum of HCO2H in . 1,4-dibromobutane, Br(CH2)4Br, is used in the synthesis of the dicarboxylic acid J and diamineK as shown. step 1 step 2 G step 3 H J K HO2CCH2CH2CO2H H2NCH2CH2CH2CH2CH2CH2NH2 step 4 BrCH2CH2CH2CH2Br Draw the structures of G and H in the boxes. Suggest reagents and conditions for each of steps 1 to 4. step 1 step 2 step 3 step 4  PolyamideL can be synthesised from dicarboxylic acidJ, HO2C(CH2)2CO2H, and diamineK, H2N(CH2)6NH2. Draw the repeat unit of the polymer formed in the box. Any functional groups should be shown displayed. polyamide L  
7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
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3-aminobenzoicacid can be synthesised from methylbenzene in three steps. methylbenzene 3-aminobenzoic acid step 1 step 2 step 3 M N CO2H NH2 Draw the structures of M and N in the boxes. Suggest reagents and conditions for each step of the synthesis. step 1 step 2 step 3  A mixture of serine, HOCH2CH(NH2)CO2H, and lysine, H2N(CH2)4CH(NH2)CO2H, reacts to form several different products. Draw the structures of the two structural isomers with the molecular formula C6H12N2O5 that could be present in the product mixture. The functional group formed in each case should be displayed.  Predict the number of different structural isomers with the molecular formula C9H19N3O4 that could be present in the product mixture. molecular formula number of structural isomers formed C9H19N3O4  Glutathione is a naturally occurring compound found in plants. glutathione O O O H NH2 O OH SH HO H N N On the diagram of glutathione, label each chiral centre with an asterisk (*). Draw the structures of the three products formed after complete acid hydrolysis of glutathione. Assume the thiol group, –SH, does not react.  Glutathione is soluble in water. By referring to the structure of glutathione, explain why glutathione is soluble in water. 
21. Organic synthesis  →  21.1. Organic synthesis
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The sketch graph for the titration of ethanoicacid, CH3CO2H, with sodiumhydroxide is shown. volume of sodium hydroxide / cm3 pH equivalence point In the region circled on the graph, identify the two organic species that are present in the solution. Explain why the pH of the mixture only changes slowly and gradually in this region when sodium hydroxide is being added. two species present The equivalence point in this acid-base titration is where the two solutions have been mixed in exactly equal molar proportion. Suggest why the pH is greater than 7 at the equivalence point in this titration. An impure sample of ammoniumvanadate(, NH4VO3, with mass 0.150 g, is dissolved in an excess of dilute acid. In this solution all vanadium is present as VO2 + ions. An excess of zinc powder is added to the solution and all the VO2 + ions are reduced to V2+ ions. The mixture is filtered to remove any remaining zinc powder. VO2 + + 4H+ + 3e– → V2+ + 2H2O When the resulting solution is titrated, 20.10 cm3 of 0.0250 mol dm–3 acidified MnO4 – oxidises all V2+ ions back to VO2 + ions. MnO4 – + 8H+ + 5e– Mn2+ + 4H2O Calculate the percentage by mass of NH4VO3 in the 0.150 g impure sample of NH4VO3. Give your answer to three significant figures. [Mr: NH4VO3, 116.9]  percentage by mass of NH4VO3 = % 
7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases
12. Nitrogen and sulfur  →  12.1. Nitrogen and sulfur
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The carbon-13 (13C) NMR spectrum of compoundA, C8H8O2, contains six peaks. CompoundA reacts with an excess of brominewater to give compound B, C8H6Br2O2. CompoundA reacts with alkaline aqueous iodine to form a yellow precipitateC and compoundD. CompoundD reacts with PCl 5 to form compoundE, C7H5O2Cl. CompoundE reacts with propan-2-ol to form compoundF. Draw the structures of compounds A, B, C, D, E and F in the boxes. A C8H8O2 C yellow ppt. D F B C8H6Br2O2 E C7H5O2Cl alkaline I2Br2PCl 5 + propan-2-ol 
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
17. Carbonyl compounds  →  17.1. Aldehydes and ketones
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