9701_s22_qp_42
A paper of Chemistry, 9701
Questions:
9
Year:
2022
Paper:
4
Variant:
2
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1
The solubility of the Group2 hydroxides increases down the group. Explain this trend. The solubility of Be(OH)2 in water is 2.40×10–6 g dm–3 at 298 K. Write an expression for the solubility product, Ksp, of Be(OH)2 and state its units. Ksp =  units =  Calculate the numerical value of Ksp for Be(OH)2 at 298 K.  Ksp = Be(OH)2 is soluble in aqueous solutions containing an excess of hydroxide ions and forms the complex ion [Be(OH)4]2–. This complex ion has a similar shape to that of [CuCl 4]2–. Define the term complex ion. Draw a three-dimensional diagram to show the structure of the complex ion [Be(OH)4]2–. Name the shape of the [Be(OH)4]2– complex ion. shape  Explain why transition elements can form complex ions. Complete Table1.1 to show the coordination number of each metal ion, and the shapes and overall polarities of the complex ions listed. Table 1.1 complex ion shape coordination number polar or non-polar cis-[Pt(H2NCH2CH2NH2)Cl 2] square planar [Ag(NH3)2]+ non-polar [Fe(C2O4)3]3–  Define stability constant, Kstab. Nickel can form complexes with the ligands en, H2NCH2CH2NH2, and tn, H2NCH2CH2CH2NH2, as shown. equilibrium1 [Ni(H2O)6]2+ + 3en [Ni3]2+ + 6H2O Kstab = 6.76 × 1017 equilibrium2 [Ni(H2O)6]2+ + 3tn [Ni3]2+ + 6H2O Kstab = 1.86 × 1012 Construct an expression for the stability constant, Kstab, for equilibrium1. State the units for Kstab. Kstab =  units =  Describe what the Kstab values indicate about the position of equilibrium for equilibrium1 and 2. Use the Kstab values to deduce which complex, [Ni3]2+ or [Ni3]2+, is more stable. 
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
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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Explain why transition elements have variable oxidation states. Sketch the shape of a 3dxy orbital. z x y  Explain why transition elements form coloured compounds. Aqueous solutions of copper(salts contain [Cu(H2O)6]2+ ions. Equilibrium3 and equilibrium4 show two reactions of these ions. equilibrium 3 [Cu(H2O)6]2++ 2OH–Cu(OH)2+ 6H2Oequilibrium 4 [Cu(H2O)6]2++ 4NH3[Cu(NH3)4(H2O)2]2++ 4H2OState the colour of Cu(OH)2and [Cu(NH3)4(H2O)2]2+. colour of Cu(OH)2colour of [Cu(NH3)4(H2O)2]2+ Use Le Chatelier’s principle to explain why a precipitate is formed when NaOHis added dropwise to [Cu(H2O)6]2+. There are two possible stereoisomers with the formula [Cu(NH3)4(H2O)2]2+. Draw three-dimensional diagrams to show the two stereoisomers. Cu Cu  
9. The Periodic Table: chemical periodicity  →  9.2. Periodicity of chemical properties of the elements in Period 3
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
6. Electrochemistry  →  6.1. Redox processes: electron transfer and changes in oxidation number (oxidation state)
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Define first electron affinity. The first electron affinity of an atom is usually an exothermic process, whereas the second electron affinity is an endothermic process. Suggest why. Describe the general trend in first electron affinities for Cl, Br and I. Explain your answer. Table3.1 shows energy changes to be used in this question and in . Table 3.1 energy change value / kJ mol–1 standard enthalpy change of atomisation of zinc +131 first ionisation energy of zinc +906 second ionisation energy of zinc +1733 standard enthalpy change of formation of ZnI2–208 lattice energy, , of zinc iodide, ZnI2–2605 first ionisation energy of iodine +1008 second ionisation energy of iodine +1846 I–I bond energy +151 enthalpy change of sublimation of iodine, I2→ I2+62 Calculate the first electron affinity for iodine. Use relevant data from Table3.1 in your working. It may be helpful to draw a labelled energy cycle. Show all working.  first electron affinity for iodine = kJ mol–1 Predict how of CdI2differs from of ZnI2. Place a tick (✓) in the appropriate box in Table3.2. Table 3.2 of CdI2is less negative than of ZnI2of CdI2is the same as of ZnI2of CdI2is more negative than of ZnI2Explain your answer. 
1. Atomic structure  →  1.4. Ionisation energy
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Calciumcarbonate decomposes on heating. CaCO3→ CaO+ CO2Table 4.1 shows the values of the Gibbs free energy change, ∆G o, for this reaction at various temperatures. Table 4.1 T / K ∆G o / kJ mol–1 9.9 4.3 –1.3 –5.8 –10.3 Assume the standard enthalpy change, ∆H o, and the standard entropy change, ∆S o, for this reaction remain constant over this temperature range. Use the data in Table4.1 to plot a graph of ∆G o against T on the grid. 12.5 10.0 7.5 5.0 2.5 0.0 –2.5 –5.0 –7.5 –10.0 –12.5 T / K G o / kJ mol–1  Calculate the gradient of your graph. Determine the ∆S o in J K–1 mol–1 for this reaction. Show all working. ∆S o = J K–1 mol–1 Group1 hydrogencarbonates, MHCO3, decompose on gentle heating to give the corresponding metal carbonate, carbondioxide and water vapour. Write an ionic equation for the decomposition of the hydrogencarbonate ion. The thermal stability of Group1 hydrogencarbonates increases down the group. Suggest an explanation for the trend in thermal stability of the Group1 hydrogencarbonates. The buffer system in seawater contains a mixture of HCO3 – and H2CO3. equilibrium 5 H2CO3 + H2O HCO3 – + H3O+ Define a buffer solution. Construct two equations to show how equilibrium5 acts as a buffer solution. The [HCO3 –] / [H2CO3] ratio in a sample of seawater is 14.1. Calculate the pH of this sample. [pKa: H2CO3, 6.35]  pH = 
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
7. Equilibria  →  7.1. Chemical equilibria: reversible reactions, dynamic equilibrium
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Complete Table5.1 to predict the substance liberated at each electrode during electrolysis of the indicated electrolyte with inert electrodes. Table 5.1 electrolyte substance liberated at the anode substance liberated at the cathode PbBr2concentrated NaCl Cu(NO3)2 An electrolytic cell is set up to determine a value for the Avogadro constant, L. The electrolyte is dilute sulfuricacid and both electrodes are copper. When a current of 0.600 A is passed through the acid for 30.0minutes, the anode decreases in mass by 0.350 g. State the relationship between the Faraday constant, F, and the Avogadro constant, L. Use the experimental information in and data from the table on page23 to calculate a value for the Avogadro constant, L. Show all working.  Avogadro constant, L = 
2. Atoms, molecules and stoichiometry  →  2.2. The mole and the Avogadro constant
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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The reagent and conditions required for the nitration of benzene, benzoicacid and phenol are shown in Table6.1. Table 6.1 compound reagents and conditions for nitration benzene concentrated HNO3, 50 °C, concentrated H2SO4 catalyst benzoic acid concentrated HNO3, 100 °C, concentrated H2SO4 catalyst phenol dilute HNO3, 20 °C Concentrated HNO3 reacts with concentrated H2SO4 to generate the electrophile NO2 +. Complete Fig.6.1 to show the mechanism of the reaction between benzene and NO2 +. Include all relevant curly arrows and charges. NO2 +  Write an equation to show how H2SO4 is regenerated. Draw the major products from the mononitration of benzoic acid and of phenol. major product from benzoic acid major product from phenol  Compare the relative ease of nitration of benzene, benzoic acid and phenol. Explain your reasoning; include reference to the structures of the three compounds in your answer. > > easiest least easy  The azo compound Congo Red is used as an acid–base indicator and can be made by the route shown in Fig.6.2. In step 3 of this synthesis, compoundY reacts with compoundZ. CompoundZ is made from compoundX. Assume that the –SO3 – Na+ groups do not react. O2N NH2 N N SO3 – Na+ NO2 step 1 step 2 step 3 Congo Red NaOHX C12H12N2 Z + Y C10H8NO3SNa NH2 SO3 – Na+ N N Suggest structures for compounds X, Y and Z and draw them in the boxes in Fig.6.2. Give the reagents and conditions for step1 and step2. step 1 step 2  
21. Organic synthesis  →  21.1. Organic synthesis
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
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State the uses of TMS and D2O in NMR spectroscopy. TMS D2O  The three isomeric ketones with molecular formula C5H10O are: ● pentan-2-one ● pentan-3-one ● 3-methylbutanone. Complete Table 7.1 to show the number of peaks observed in the proton (1H) NMR spectrum and in the carbon-13 NMR spectrum for each compound listed. Table 7.1 ketone number of peaks observed in the proton (1H) NMR spectrum number of peaks observed in the carbon-13 NMR spectrum pentan-2-one pentan-3-one 3-methylbutanone  State all the ketones with molecular formula C5H10O that have: a doublet in their proton (1H) NMR spectrum a singlet in their proton (1H) NMR spectrum.  Cortisone, C21H28O5, is a naturally occurring chemical that contains chiral carbon atoms. CH3 O O O CH3 OH OH cortisone Deduce the number of chiral carbon atoms in one molecule of cortisone. Cortisone is reacted with an excess of NaBH4. State the molecular formula of the organic compound formed. Cortisone is an optically active molecule. Explain what is meant by optically active. 
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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Compare the relative acidities of ethanol, ethanoic acid, chloroethanoic acid and phenol. Explain your reasoning. > > > most acidic least acidic  An excess of ethanedioicacid, HOOCCOOH, is reacted with warm acidified KMnO4. State the type of reaction undergone by ethanedioicacid. Describe what you would observe. Write an equation for this reaction. Your equation can use [O] or [H] as necessary. type of reaction observations equation  A section of a polyester is shown. O C O CH2 CH3 O C CH O O polyester C O CH2 CH3 O C CH O Draw the structures of the two monomers that form this polyester.  Serine can polymerise to form two different types of condensation polymer; a polyester and a polypeptide. H2C H2N C serine H C O OH OH Draw the structure of the polypeptide showing two repeat units. The peptide linkage should be shown displayed.  Explain why condensation polymers normally biodegrade more readily than addition polymers. 
14. Hydrocarbons  →  14.2. Alkenes
11. Group 17  →  11.4. The reactions of chlorine
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
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The structure of cyclohexylamine is shown in . NH2 cyclohexylamine Compare the relative basicities of ammonia, cyclohexylamine and phenylamine. Explain your reasoning. > > most basic least basic  Cyclohexylamine reacts with ethanoylchloride to form the corresponding amide, L. NH2 HN C O L CH3COCl CH3 Name the mechanism for the reaction shown in Fig.9.2. Complete the mechanism of the reaction between cyclohexylamine and CH3COCl. R–NH2 is used to represent cyclohexylamine. Include all relevant lone pairs of electrons, curly arrows, charges and partial charges. H3C C products O Cl R NH2  The reaction between cyclohexylamine and an excess of CH3COCl forms compoundM. CompoundM has the molecular formula C10H17NO2. Suggest and draw the structure of M.  
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
13. An introduction to AS Level organic chemistry  →  13.2. Characteristic organic reactions
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