9701_s24_qp_41
A paper of Chemistry, 9701
Questions:
9
Year:
2024
Paper:
4
Variant:
1
Login to start this paper & get access to powerful tools
1
Describe the trend in the solubility of the hydroxides of magnesium, calcium and strontium. Explain your answer. > > most soluble least soluble Suggest the variation in pH of saturated solutions of the hydroxides of magnesium, calcium and strontium. Explain your answer. Barium hydroxide, Ba(OH)2, is a strong base. A 250.0 cm3 solution of Ba(OH)2 with a pH of 12.2 is made by dissolving Ba(OH)2 in distilled water. Calculate the mass of Ba(OH)2 required to make this solution. Show your working. [Mr: Ba(OH)2, 171.3] mass of Ba(OH)2 = g The solubility of iron(hydroxide, Fe(OH)2, is 5.85 × 10–6 mol dm–3 at 298 K. Write the expression for the solubility product, Ksp, of Fe(OH)2. Ksp = Calculate the value of Ksp of Fe(OH)2. Include its units. Ksp = units =
10. Group 2  →  10.1. Similarities and trends in the properties of the Group 2 metals, magnesium to barium, and their compounds
Open
2
Define transition element. Explain why transition elements can form complex ions. The 3d orbitals in an isolated Ag+ ion are degenerate. Define degenerate d orbitals. Sketch the shape of a 3dxy orbital in . z y x Tollens’ reagent can be used to distinguish between aldehydes and ketones. Tollens’ reagent contains [Ag(NH3)2]OH, which can be prepared in a two-step process. step 1 Aqueous NaOH is added dropwise to aqueous AgNO3 to form Ag2O as a brown precipitate. step 2 Aqueous NH3 is added dropwise to Ag2O to form a colourless solution containing [Ag(NH3)2]OH. Construct equations for each of the steps in the preparation of [Ag(NH3)2]OH. step 1 step 2 Name the shape of the complex ion [Ag(NH3)2]+. State the bond angle for H-N-Ag and for N-Ag-N. shape bond angle for H-N-Ag = ° bond angle for N-Ag-N = ° An electrochemical cell uses Ag2O as the positive electrode and Zn as the negative electrode immersed in an alkaline electrolyte. The overall cell reaction is shown. Ag2O + Zn + H2O 2Ag + Zn(OH)2 Complete the half-equation for the reaction at each electrode. at the positive electrode Ag2O + at the negative electrode Zn + Coordination polymers are made when a bidentate ligand acts as a bridge between different metal ions. Under certain conditions Ru3+and the bidentate ligand dps can form a coordination polymer containing ([RuCl 4]–)n chains. N N S dps The bidentate ligand dps uses each of the nitrogen atoms to bond to a different Ru3+. Complete by drawing the structure for the coordination polymer ([RuCl 4]–)n. Show two repeat units. The dps ligand can be represented using N N . Ru
11. Group 17  →  11.3. Some reactions of the halide ions
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
14. Hydrocarbons  →  14.2. Alkenes
Open
3
When a sample of hydrated lithium ethanedioate, Li2C2O4•H2O, is gently heated, two gaseous products are formed and a white solid residue remains. The residue is added to HNO3. A gas is produced that turns limewater milky. Complete the equation for the decomposition of Li2C2O4•H2O. Li2C2O4•H2O + + The trend in the decomposition temperatures of the Group 2 ethanedioates is similar to that of the Group 2 nitrates. Suggest which of CaC2O4 and BaC2O4 will decompose at the lower temperature. Explain your answer. Potassium iron(ethanedioate, K3[Fe(C2O4)3], dissolves in water to form a green solution. Explain why transition elements can form coloured complexes. The anhydrous iron(compound K3[Fe(C2O4)3] decomposes on heating to form a mixture of K2[Fe(C2O4)2], K2C2O4 and CO2. Complete the equation for the decomposition of K3[Fe(C2O4)3]. K3[Fe(C2O4)3] K2[Fe(C2O4)2] + K2C2O4 + CO2 The [Fe(C2O4)3]3– complex ion shows stereoisomerism. Complete the three-dimensional diagrams in to show the two stereoisomers of [Fe(C2O4)3]3–. The C2O4 2– ligand can be represented using O O. isomer 1 Fe isomer 2 Fe Buffer solutions are used to regulate pH. Write two equations to describe how a solution containing HC2O4 – ions acts as a buffer solution when small amounts of acid or alkali are added. A fuel cell is an electrochemical cell that can be used to generate electrical energy by using oxygen to oxidise a fuel. Ethanedioic acid, (COOH)2, dissolved in an alkaline electrolyte is being investigated as a fuel. The relevant standard electrode potentials, Eo, for the cell are shown. O2+ 2H2O+ 4e– 4OH–Eo = +0.40 V 2CO2+ 2e– C2O4 2–Eo = –0.59 V Use these equations to deduce the overall cell reaction. Calculate the value of E o cell. overall cell reaction E o cell = V
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  →  11.4. The reactions of chlorine
Open
4
Define standard electrode potential, Eo, including a description of standard conditions. An electrochemical cell is set up to measure Eo of the Ag+/Agelectrode. Draw a labelled diagram of this electrochemical cell. Include all necessary substances. It is not necessary to state conditions used. A separate electrochemical cell is set up using a lower concentration of Ag+than that used in . Suggest how the electrode potential, E, for the Ag+/Agelectrode would change from its Eo value. Explain your answer. Define enthalpy change of solution, ΔH o sol . Some relevant energy changes for AgNO3 are shown in Table 4.1. Table 4.1 energy change value / kJ mol–1 enthalpy change of solution of AgNO3+22.6 enthalpy change of hydration of silver ions –475 enthalpy change of hydration of nitrate ions –314 Complete the energy cycle in to show the relationship between the lattice energy, ΔH o latt , of AgNO3and the energy changes shown in Table 4.1. Include state symbols for all the species. AgNO3Calculate the lattice energy, ΔH o latt , of AgNO3. ΔH o latt = kJ mol–1 Suggest the trend in the magnitude of the lattice energies of the metal nitrates, NaNO3, Mg(NO3)2and RbNO3. Explain your answer. most exothermic least exothermic
5. Chemical energetics  →  5.1. Enthalpy change, \(\Delta H\)
11. Group 17  →  11.3. Some reactions of the halide ions
2. Atoms, molecules and stoichiometry  →  2.3. Formulas
Open
5
In aqueous solution, persulfate ions, S2O8 2–, react with iodide ions, as shown in reaction 1. reaction 1 S2O8 2– + 2I– 2SO4 2– + I2 The rate of reaction 1 is investigated. A sample of S2O8 2– is mixed with a large excess of iodide ions of known concentration. The graph in shows the results obtained. 0.000 0.100 0.200 0.300 0.400 0.500 0.600 0.700 0.800 0.900 time / min [S2O8 2–] / mol dm–3 Use to determine the initial rate of reaction 1. Show your working. rate = mol dm–3 min–1 The rate equation for reaction 1 is rate = k [S2O8 2–] [I–]. Suggest why a large excess of iodide ions allows the rate constant to be determined from the half-life in this investigation. The reaction of persulfate ions, S2O8 2–, with iodide ions is catalysed by Fe2+ ions. Write two equations to show how Fe2+ catalyses reaction 1. equation 1 equation 2 Describe the effect of an increase in temperature on the rate constant and the rate of reaction 1. In aqueous solution, thiosulfate ions, S2O3 2–, react with hydrogen ions, as shown in reaction 2. reaction 2 S2O3 2– + 2H+ SO2 + S + H2O The rate of reaction is first order with respect to [S2O3 2–] and zero order with respect to [H+] under certain conditions. The rate constant, k, for this reaction is 1.58 × 10–2 s–1. Calculate the half-life, t 1 2, for reaction 2. t 1 2 = s The compound nitrosyl bromide, NOBr, can be formed as shown in reaction 3. reaction 3 2NO+ Br22NOBrThe rate is first order with respect to [NO] and first order with respect to [Br2]. The reaction mechanism has two steps. Suggest equations for the two steps of this mechanism. State which is the rate-determining step. step 1 step 2 rate-determining step =
8. Reaction kinetics  →  8.1. Rate of reaction
8. Reaction kinetics  →  8.2. Effect of temperature on reaction rates and the concept of activation energy
Open
6
State what is meant by partition coefficient, Kpc. The partition coefficient, Kpc, for a compound, X, between carbon disulfide, CS2, and water is 10.5. 1.85 g of X is dissolved in water and made up to 100.0 cm3 in a volumetric flask. 40.0 cm3 of this aqueous solution is shaken with 25.0 cm3 of CS2. The mixture is left to reach equilibrium. Calculate the mass of X, in g, extracted into the CS2 layer. mass of X = g The compound C6H6 has many structural isomers. Four suggested structures of C6H6 are shown in . delocalised benzene Kekulé benzene Dewar benzene Ladenburg benzene Using , complete Table 6.1 to predict the number of carbon atoms that have sp, sp2 and sp3 hybridisation in Kekulé benzene, Dewar benzene and Ladenburg benzene. Table 6.1 C6H6 structure sp hybridised sp2 hybridised sp3 hybridised Kekulé benzene Dewar benzene Ladenburg benzene Describe the shape of delocalised benzene. Include the geometry of each carbon, the C-C-H bond angle and the type of bondbetween the carbon atoms and between the carbon and hydrogen atoms. Suggest why Dewar benzene and Ladenburg benzene are unstable isomers of C6H6. Complete Table 6.2 to predict the number of peaks in the proton (1H) NMR spectrum for Dewar benzene, Ladenburg benzene and delocalised benzene. Table 6.2 number of peaks Dewar benzene Ladenburg benzene delocalised benzene The reaction of phenylethanone with 1,4-dibromobutane, BrCH2CH2CH2CH2Br, in the presence of FeBr3 is shown in . O O BrCH2CH2CH2CH2Br phenylethanone FeBr3 + Br + HBr The mechanism of this reaction is similar to that of the alkylation of benzene. Construct an equation for the formation of the electrophile, BrCH2CH2CH2CH2 +. Complete the mechanism in for the reaction of phenylethanone with BrCH2CH2CH2CH2 + ions. Include all relevant curly arrows and charges. Draw the structure of the organic intermediate. O O BrCH2CH2CH2CH2 organic intermediate + Br + The reaction shown in forms small amounts of two by-products, Y (C20H22O2) and Z (C12H14O). Suggest structures for Y and Z in the boxes in . Y (C20H22O2) Z (C12H14O)
14. Hydrocarbons  →  14.2. Alkenes
13. An introduction to AS Level organic chemistry  →  13.3. Shapes of organic molecules; σ and π bonds
22. Analytical techniques  →  22.2. Mass spectrometry
Open
7
Four esters, A, B, C and D, with the molecular formula C6H12O2 are shown in . O O O O O O O O A B C D Give the systematic name of ester A. A mixture of these esters, A, B, C and D, is analysed by gas–liquid chromatography. The chromatogram produced is shown in . The number above each peak represents the area under the peak. The area under each peak is proportional to the mass of the respective ester in the mixture. detector response ester C ester B ester A ester D time / min State what is meant by retention time. Calculate the percentage by mass of ester D in the original mixture. percentage by mass of ester D = % Separate samples of the esters, A, B, C and D, are analysed using proton (1H) NMR and carbon-13 NMR spectroscopy. Complete Table 7.1 to show the number of peaks in each NMR spectrum for esters B and C. Table 7.1 ester number of peaks in proton (1H) NMR spectrum number of peaks in carbon-13 NMR spectrum B C Identify all of the esters from A, B, C and D that have at least one triplet peak in their proton (1H) NMR spectrum. Question 7 continues on page 20. Compound F, C6H8O3, shows stereoisomerism and effervesces with Na2CO3. Compound F reacts with alkaline I2to form yellow precipitate G and compound H. Compound F reacts with LiAl H4 to form compound J, C6H12O2. Compound F reacts with SOCl 2 to form compound K, C6H7O2Cl . Compound K reacts with propan-2-ol to form compound L. Draw the structures of compounds F, G, H, J, K and L in the boxes in . F, C6H8O3 alkaline I2+ J, C6H12O2 LiAl H4 SOCl 2 K, C6H7O2Cl L propan-2-ol G H
18. Carboxylic acids and derivatives  →  18.2. Esters
22. Analytical techniques  →  22.2. Mass spectrometry
Open
8
Neotame is an artificial sweetener added to some foods. N N H H O neotame O O O OH State the number of chiral carbon atoms in a molecule of neotame. Neotame contains the arene functional group. Identify all the other functional groups present in neotame. Neotame reacts with an excess of hot NaOHto form three organic products. State the two types of reaction that occur when neotame reacts with hot NaOH. N N H H O neotame O O O OH Draw the structures of the three organic products formed from the reaction of neotame with an excess of hot NaOH.
21. Organic synthesis  →  21.1. Organic synthesis
14. Hydrocarbons  →  14.2. Alkenes
13. An introduction to AS Level organic chemistry  →  13.1. Formulas, functional groups and the naming of organic compounds
Open
9
Samples of phenol, C6H5OH, are reacted separately with sodium and with dilute nitric acid. phenol OH Write the equation for the reaction of C6H5OH with Na. Draw the structures of the two major isomeric organic products formed in the reaction of phenol with dilute HNO3. Salicylic acid can be synthesised from phenol. salicylic acid OH COOH One of the steps in this synthesis is the electrophilic substitution reaction of carbon dioxide with the phenoxide ion, C6H5O–. Complete the mechanism in for the reaction of C6H5O– with CO2. Include all relevant curly arrows, dipoles and charges. Draw the structure of the organic intermediate. O– O– + C O O COO– organic intermediate Some syntheses use Diels–Alder reactions, which normally involve a diene and an alkene reacting together to form a cyclohexene. Draw three curly arrows in to complete the mechanism for the Diels–Alder reaction between buta-1,3-diene and ethene. buta-1,3-diene cyclohexene ethene + Another Diels–Alder reaction of buta-1,3-diene is shown in . Predict the product formed in this reaction. +
18. Carboxylic acids and derivatives  →  18.1. Carboxylic acids
14. Hydrocarbons  →  14.2. Alkenes
Open