9701_s19_qp_42
A paper of Chemistry, 9701
Questions:
8
Year:
2019
Paper:
4
Variant:
2
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1
Complete the electronic configuration of the copper(ion. 1s22s22p6 State the colour of the solutions containing the following ions. ● [Cu(H2O)6]2+● [CuCl 4]2– Octahedral complexes of Cu2+ with different ligands can have different colours. Explain why. Copper(and silver(salts are colourless. Suggest why. Consider the following two equilibria and associated data values at 298 K. AgBrAg++ Br –equilibrium1 Ksp = 5.0 × 10–13 mol2 dm–6 Ag++ 2NH3[Ag(NH3)2]+equilibrium2 Kstab = 1.7 × 107 mol–2 dm6 The equilibrium constant for equilibrium1 is the solubility product, Ksp, of AgBr. The equilibrium constant for equilibrium2 is the stability constant, Kstab, for the formation of [Ag(NH3)2]+. Calculate the solubility of AgBr at 298 K in mol dm–3.  solubility of AgBr = mol dm–3 Use Le Chatelier’s principle as applied to equilibria 1 and 2 to suggest why AgBrdissolves in concentrated NH3. Use equilibria1 and 2 to construct an equation for the reaction of AgBrwith concentrated NH3. This is equilibrium3. equilibrium3 Write an expression for the equilibrium constant of equilibrium 3, Keq3, in terms of Ksp for equilibrium1 and Kstab for equilibrium2. Keq3 =  Define the term standard electrode potential, E o. Complete and label the diagram to show how the standard electrode potential, E o, of Ag+/ Agcould be measured under standard conditions.  Use the Data Booklet to label the diagram in to show ● ● which is the positive electrode, ● ● the direction of electron flow in the external circuit when a current flows.  
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
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Group2 carbonates decompose when heated. Write an equation for the decomposition of the carbonate ion. Describe and explain how the thermal stability of the Group 2 carbonates changes with increasing atomic number. Lead(carbonate, PbCO3, and zinc carbonate, ZnCO3, decompose on heating in a similar way to calciumcarbonate, CaCO3. State relevant data from the Data Booklet and use it to predict the order of thermal stability of these three carbonates. data (most stable) > > (least stable)  Dolomite contains the double carbonate of calcium and magnesium, CaMg(CO3)2, and some impurities. When 0.642 g of a sample of dolomite reacts with an excess of hydrochloricacid, 125.0 cm3 of CO2 is formed under room conditions. Calculate the percentage of CaMg(CO3)2 in the sample of dolomite. Show all your working. Assume that none of the impurities react with HCl.  % of CaMg(CO3)2 in dolomite = %  
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  →  11.2. The chemical properties of the halogen elements and the hydrogen halides
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Sketch the shape of a d orbital.  Explain what is meant by the term transition element. Transition elements can form complex ions which contain ligands. Name the type of bonding that occurs between a ligand and a transition element. Give the formulae of two oxides of iron. State the oxidation number of iron in each compound. CO and CN– are monodentate ligands. Complete the table for the following two complexes. metal ion ligand co-ordination number formula of complex ion charge of complex ion Ni2+ CO Fe3+ CN– 3-  Transition element complexes can exhibit stereoisomerism. [Cu(H2O)4(NH3)2]2+ and Pt(NH3)2Cl 2 show the same type of isomerism. Name this type of isomerism. Complete the three-dimensional diagrams of the two isomers for [Cu(H2O)4(NH3)2]2+ and Pt(NH3)2Cl 2. Cu Cu Pt Pt  Copper can form complexes with the ligands ammonia and en, H2NCH2CH2NH2, as shown. [Cu(H2O)6]2++ en[Cu(H2O)4]2++ 2H2OKstab = 3.98 × 1010 equilibrium4 [Cu(H2O)6]2++ 2NH3[Cu(H2O)4(NH3)2]2++ 2H2OKstab = 5.01 × 107 equilibrium5 Write an expression for the stability constant, Kstab, for equilibrium5. State its units. Kstab =  units =  The standard entropy change, ΔS o, for equilibrium4 is +23 J K–1 mol–1 and for equilibrium5 is –8.4 J K–1 mol–1. Suggest an explanation for this difference by reference to both equilibria. Of the three copper complexes in equilibria 4 and 5, state the formula of the copper complex that is the most stable and explain your choice. copper complex explanation  
3. Chemical bonding  →  3.4. Covalent bonding and coordinate (dative covalent) bonding
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
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The initial rate of reaction for propanone and iodine in acid solution is measured in a series of experiments at a constant temperature. H+ catalyst CH3COCH3 + I2 CH3COCH2I + HI The rate equation was determined experimentally to be as shown. rate = k [CH3COCH3][H+] State the order of reaction with respect to ● CH3COCH3 ● I2 ● H+ and state the overall order of this reaction.  The rate of this reaction is 5.40 × 10–3 mol dm–3 s–1 when ● the concentration of CH3COCH3 is 1.50 × 10–2 mol dm–3 ● the concentration of I2 is 1.25 × 10–2 mol dm–3 ● the concentration of H+ is 7.75 × 10–1 mol dm–3. Calculate the rate constant, k, for this reaction. State the units of k.  k =  units =  Complete the table by placing one tick () in each row to describe the effect of decreasing the temperature on the rate constant and on the rate of reaction. decreases no change increases rate constant rate of reaction  From the results, a graph is produced which shows how the concentration of I2 changes during the reaction. [I2] time Describe how this graph could be used to determine the initial rate of the reaction. On the axes below, sketch a graph to show how the initial rate changes with different initial concentrations of CH3COCH3 in this reaction. rate [CH3COCH3]  The rate of a reaction between metal ions was studied. The following three-step mechanism has been suggested for this reaction. Step1 is the rate-determining step. step 1 Ce4+ + Mn2+ Ce3+ + Mn3+ step 2 Ce4+ + Mn3+ Ce3+ + Mn4+ step 3 Mn4+ + Tl + Tl 3+ + Mn2+ Explain the meaning of the term rate-determining step. Use this mechanism to ● determine the overall equation for this reaction ● suggest the role of Mn2+ ions in this mechanism. Explain your answer.  
8. Reaction kinetics  →  8.2. Effect of temperature on reaction rates and the concept of activation energy
8. Reaction kinetics  →  8.1. Rate of reaction
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Complete the table by placing one tick () in each row to indicate the sign of each type of energy change under standard conditions. energy change always positive always negative either negative or positive lattice energy enthalpy change of neutralisation  Define, in words, the term enthalpy change of solution. The following enthalpy changes are given. enthalpy change value / kJ mol–1 standard enthalpy change of formation, , for K3PO4–2035 standard enthalpy change, ∆H o, for P+ 2O2+ 3e– PO4 3––1284 standard enthalpy change, ∆H o, for KK++ e– –251 Determine the standard enthalpy change of solution of potassium phosphate, K3PO4. It may be helpful to draw a labelled energy cycle.  = kJ mol–1 Some lattice energy values are shown in the table. compound lattice energy value / kJ mol–1 CaBr2–2176 KBr–679 Suggest an explanation for why CaBr2 is more exothermic than KBr. For a particular gas phase reaction the variation in standard Gibbs free energy change, ΔG o, with temperature is shown. Assume standard enthalpy change, ΔH o, and standard entropy change, ΔS o, remain constant with temperature. ∆G o / kJ mol–1 T / K Write the equation that relates ΔG o to ΔH o and ΔS o. Use this equation to explain why ΔG o becomes less positive as temperature increases in this reaction. 
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
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By reference to the formation of σ and π bonds, describe and explain the shape of a benzene molecule, C6H6. 2,3-dimethylphenylamine can be prepared from 1,2-dimethylbenzene in two steps as shown. 1,2-dimethylbenzene CH3 CH3 M CH3 CH3 NO2 2,3-dimethylphenylamine CH3 CH3 NH2 HNO3 / H2SO4 step 1 step 2 Step1 is catalysed by H2SO4. Write an equation to show how H2SO4 generates the electrophile during step1. Draw the mechanism of the reaction between this electrophile and 1,2-dimethylbenzene to form M. Include all relevant curly arrows and charges. intermediate CH3 CH3 M CH3 CH3 NO2  Write an equation to show how the H2SO4 catalyst is reformed. For step2, suggest the reagents and conditions and name the type of reaction. ● reagents and conditions ● type of reaction  The drug mefenamic acid can be made using 2,3-dimethylphenylamine in an excess of 2‑chlorobenzoic acid. 2,3-dimethylphenylamine CH3 CH3 2-chlorobenzoic acid mefenamic acid CO2H CO2H Cl + + HCl NH2 CH3 CH3 N H Deduce the molecular formula of mefenamic acid. Name the functional groups, apart from the benzene ring, in mefenamic acid. Calculate the maximum mass of mefenamic acid that could be formed from 5.00 g of 2,3‑dimethylphenylamine in this reaction. Give your answer to three significant figures.  mass of mefenamic acid = g The position of substitution in the electrophilic substitution of arenes can be explained based on the stability of the intermediate cations formed in the first step. The example given involves the bromination of methylbenzene. methylbenzene CH3 CH3 + CH3 3-position 2-position 4-position Br H Br H CH3 + + Br H Use this information and your knowledge about the stability of cations to suggest why the CH3 group directs incoming electrophiles to the 2- and 4-positions in preference to the 3-position. 
14. Hydrocarbons  →  14.2. Alkenes
14. Hydrocarbons  →  14.1. Alkanes
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Amino acids can be separated by thin-layer chromatography. A mixture of amino acids is analysed using this technique. The chromatogram obtained is shown, drawn to scale. The table shows some Rf values for different amino acids in the solvent used. cm baseline solvent front amino acid Rf value alanine 0.40 glutamic acid 0.29 leucine 0.71 valine 0.61 A B Use the chromatogram and the Rf values to deduce the amino acid responsible for spotA and spotB. amino acid responsible for spotA amino acid responsible for spotB  A second chromatogram of the same mixture is taken using a more polar solvent. Predict the effect on the Rf values of the amino acids. Explain your reasoning. Glycine, H2NCH2CO2H, is the simplest amino acid. Complete the equations to show the acid-base properties of glycine. H2NCH2CO2H+ HCl H2NCH2CO2H+ NaOH In aqueous solution, amino acids exist as zwitterions. Draw the zwitterionic structure of glycine. Explain how the zwitterion for glycine is formed.  Apart from glycine, all naturally occurring amino acids have a chiral centre and exhibit stereoisomerism. Draw the two stereoisomers of alanine, CH3CH(NH2)CO2H. C C  The amino acid alanine can be synthesised from 2‑chloropropanoic acid, CH3CHCl CO2H. State the reagents and conditions and name the mechanism for this reaction. reagents and conditions name of mechanism  State and explain the relative acidities of trichloroethanoic acid, chloroethanoic acid and ethanoic acid. Serine, HOCH2CH(NH2)CO2H, can react with alanine, CH3CH(NH2)CO2H, to form three different structural isomers, each with the molecular formula C6H12N2O4. Draw the structures of these three structural isomers. isomer 1 (C6H12N2O4) isomer 2 (C6H12N2O4) isomer 3 (C6H12N2O4)  
7. Equilibria  →  7.2. Brønsted–Lowry theory of acids and bases
11. Group 17  →  11.3. Some reactions of the halide ions
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CompoundR is shown. CH3 Cl HO R CH3 State the systematic name of compoundR. R is dissolved in CDCl 3 and analysed using carbon‑13 and proton NMR spectroscopy. ● Predict the number of peaks that are seen in the carbon-13 NMR spectrum of R. ● Predict the number of peaks that are seen in the proton NMR spectrum of R.  A separate sample of R is dissolved in D2O. The proton NMR spectrum of this solution shows one less peak than is obtained in CDCl 3. Explain why. CompoundR reacts separately with the four reagents shown in the table. Complete the table by ● drawing the structures of the organic products formed, ● stating the type of reaction. reagent organic product structure type of reaction Na CH3COCl Br2+ N N Cl –  
15. Halogen compounds  →  15.1. Halogenoalkanes
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
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