Chemistry 9701/44 May/June 2025: question paper and mark scheme

Question

(a) (i) Describe the trend in the thermal stabilities of the carbonates of the Group 2 elements. Explain your answer. …… [3] (ii) Copper(II) carbonate decomposes on heating in a similar way to the carbonates of Group 2. Write an equation for the decomposition of copper(II) carbonate. …… [1] (b) (i) Complete the electrons in boxes diagram in Fig. 1.1 to show the electronic configuration of a copper(II) ion. 3d 4s 4p [Ar] Fig. 1.1 [1] (ii) There are five different 3d orbitals. Sketch the shape of a 3dz2 orbital in Fig. 1.2. z y x Fig. 1.2 [1] (iii) Copper can form stable complexes in the +1 and +2 oxidation states. Explain why transition elements have variable oxidation states. …… [1] (c) (i) 1,2-diaminoethane, H2NCH2CH2NH2, en, can act as a bidentate ligand. Explain what is meant by a bidentate ligand. …… [2] (ii) The complex [Cu(H2O)2(en)2]2+ exists as stereoisomers. Complete the three-dimensional diagrams in Fig. 1.3 to show the three different stereoisomers of [Cu(H2O)2(en)2]2+. The en ligand can be represented using N N . isomer 1 isomer 2 Cu Cu isomer 3 Cu Fig. 1.3 [3] (iii) State the different types of stereoisomerism shown by [Cu(H2O)2(en)2]2+. …… [1] (iv) Identify one isomer in (c)(ii) that is polar. Explain your answer. isomer …… [1] (d) (i) The mineral ore cryolite, Na3Al F6, contains a single anion which is a complex ion. Complete Table 1.1 to suggest the formula of the complex ion and to identify the ligand present in Na3Al F6. Table 1.1 complex ion in Na3Al F6 ligand in Na3Al F6 [1] (ii) When a solution of Al 2O3 in molten cryolite is electrolysed, aluminium metal is formed at the cathode. The equation is shown. Al 3+ + 3e– Al Calculate the maximum mass of aluminium produced when a current of 1.5 A is passed through this solution for 30 minutes. Give your answer to two significant figures. mass of aluminium = …… g [4] [Total: 19]

Question

(a) Anhydrous barium chloride can be obtained from the hydrated salt, as shown in reaction 1. reaction 1 BaCl 2•2H2O(s) + 2SOCl 2(l) BaCl 2(s) + 2SO2(g) + 4HCl (g) (i) Describe one observation when reaction 1 is carried out. …… [1] (ii) Define the term entropy, S. …… [1] (iii) The entropy change, ΔS o , for reaction 1 at 25 °C is +768 J K–1 mol–1. Explain why ΔS o has a large positive value. …… [1] o (iv) Table 2.1 shows the enthalpy changes of formation, ΔH f , for the compounds in reaction 1. Table 2.1 o compound ΔH f / kJ mol–1 BaCl 2(s) –859 BaCl 2•2H2O(s) –1460 SOCl 2(l) –246 SO2(g) –297 HCl (g) –92 Calculate the standard Gibbs free energy change, ΔG o , in kJ mol–1, for reaction 1 at 25 °C. ΔG o = …… kJ mol–1 [3] (b) When aqueous solutions of BaCl 2 and Na2Cr2O7 are mixed, a yellow precipitate of BaCrO4(s) is produced and an acidic solution remains. (i) Write the ionic equation for this reaction. …… [1] (ii) Explain why BaCrO4(s) is coloured. …… [3] (c) Barium sulfate is the least soluble of the Group 2 sulfates. Explain the trend in the solubilities of the Group 2 sulfates. …… [3] [Total: 13]

Question

(a) Nickel(II) iodate(V), Ni(IO3)2, is sparingly soluble in water. The concentration of its saturated solution is 2.30 × 10–2 mol dm–3 at 298 K. (i) Complete the expression for the solubility product, Ksp, of Ni(IO3)2. Include the units. Ksp = units = …… [2] (ii) Calculate the numerical value for Ksp of Ni(IO3)2 at 298 K. Ksp = …… [1] (b) An electrochemical cell is set up as shown in Fig. 3.1. V Pt(s) Cu(s) Ni(IO3)2(aq) and I2(aq) CuCl 2(aq) Ni(IO3)2(s) Fig. 3.1 The relevant standard electrode potentials, E o , for this electrochemical cell are shown. 1 IO3–(aq) + 6H+(aq) + 5e– 2 I2(aq) + 3H2O(l) E o = +1.19 V Cu2+(aq) + 2e– Cu(s) E o = +0.34 V o (i) Use this information to calculate the value of E cell . State which electrode is positive. o E cell = …… positive electrode is …… [1] o (ii) Suggest how the measured Ecell of this cell compares to the E cell under standard conditions. Explain your answer. …… [1] (iii) Complete Table 3.1 by placing one tick (3) to indicate how the Ecell of this cell changes when a small amount of NiSO4(aq) is added to the beaker containing Ni(IO3)2(aq) and I2(aq) in Fig. 3.1. Explain your answer. Table 3.1 change in Ecell less positive no change more positive [2] (c) In solution, iodic(V) acid, HIO3, ionises as shown. HIO3(aq) IO3–(aq) + H+(aq) The pH of a 1.0 mol dm–3 solution of HIO3 is 0.47. (i) Calculate [H+(aq)], in mol dm–3, in a 1.0 mol dm–3 solution of HIO3. [H+(aq)] = …… mol dm–3 [1] (ii) Use your answer from (c)(i) to calculate the equilibrium concentrations of HIO3(aq) and IO3–(aq), in mol dm–3, in a 1.0 mol dm–3 solution of HIO3. [HIO3(aq)] = …… mol dm–3 [IO3–(aq)] = …… mol dm–3 [1] (iii) Use your answers from (c)(i) and (c)(ii) to calculate the Ka, in mol dm–3, of HIO3. Ka = …… mol dm–3 [1] (d) The Dushman reaction is the reaction between iodate(V) ions and iodide ions in acid solution. IO3–(aq) + 5I–(aq) + 6H+(aq) 3I2(aq) + 3H2O(l) The rate equation for this reaction is shown. rate = k [IO3–][I–]2[H+]2 The rate of this reaction is investigated in a buffer solution. The initial concentrations are shown. [IO3–] = 0.500 mol dm–3 [I–] = 1.00 × 10–3 mol dm–3 [H+] = 1.00 × 10–2 mol dm–3 Under these conditions the initial rate of the reaction is 2.10 × 10–2 mol dm–3 s–1. (i) Define buffer solution. …… [2] (ii) Use the information to calculate the rate constant, k. State its units. k = …… units = …… [2] (iii) This reaction is repeated at the same temperature and with the same initial values of [IO3–] and [I–]. The [H+] is increased to 3.00 × 10–2 mol dm–3. Calculate the initial rate of this reaction. rate = …… mol dm–3 s–1 [1] [Total: 15]

Question

Table 4.1 shows the structures of sections of three polymers, X, Y and Z. Each polymer is made from only one type of monomer. Table 4.1 polymer structure of section of polymer O O H2 O H H H HC2 C HC22 HC22 HN H H H X C 2 N C C 2 C C 2 C NH C C N C CC C C C C N C HN HC2 HC2 HC2 C H H2 H2 H2 H H2 H2 H2 O O O COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 COOCH3 CH CH CH CH CH Y CH CH CH CH CH CH C CH C CH C CH C CH CH CH CH CH HC2 2 HC2 2 HC2 2 HC2 2 H 2 H 2 H 2 H 2 O CH3 O O CH3 O O CH3 O O C CH O C O C CH O C O CH C O CH C O CH C Z CH O C CH CH O C CH CH3 O CH3 CH3 O CH3 CH3 O CH3 (a) Complete Table 4.2 to state the type of polymerisation and draw the structure of the monomer for each polymer, X, Y and Z. Table 4.2 polymer type of polymerisation structure of monomer X Y Z [4] (b) Amino acids can act as monomers. State what is meant by the isoelectric point of an amino acid. …… [1] (c) Electrophoresis can be used to separate and identify amino acids. Table 4.3 shows information about the three amino acids glycine, lysine and glutamic acid. Table 4.3 amino acid structural formula of amino acid isoelectric point glycine (gly) H2NCH2COOH 6.0 lysine (lys) H2NCH(CH2CH2CH2CH2NH2)COOH 9.7 glutamic acid (glu) H2NCH(CH2CH2COOH)COOH 3.2 (i) A mixture containing these three amino acids is analysed in a buffer solution of pH 6.0. Draw and label three spots on Fig. 4.1 to indicate the predicted position of each of these amino acids, gly, lys and glu, after electrophoresis. + – mixture applied here Fig. 4.1 [2] (ii) Electrophoresis is repeated using a buffer solution of pH 11. Predict how the position of glycine will change, if at all, after electrophoresis. …… [1] [Total: 8]

Question

A group of drugs known as statins are used to lower cholesterol in blood. A commonly used statin is atorvastatin. atorvastatin OH OH O NH N OH O F Fig. 5.1 (a) Statins can break down in the acid found in the stomach. (i) Draw a line through the bond in the atorvastatin structure in Fig. 5.1 that could be broken under acid conditions. [1] (ii) By referring to the structure, explain why atorvastatin dissolves in water. …… [1] (iii) Complete the molecular formula of atorvastatin. C H35N O F [1] (iv) Atorvastatin contains chiral carbon atoms. Circle all chiral carbon atoms in Fig. 5.1. [1] (v) The synthetic preparation of atorvastatin requires the production of a single optical isomer. Suggest why. …… [1] (b) (i) The proton (1H) NMR spectrum of atorvastatin dissolved in CDCl 3 is recorded. Use Table 5.1 to deduce the number of hydrogen atoms that could produce peaks in the region δ = 6.5–13.0 ppm. …… [1] (ii) The proton (1H) NMR spectrum of atorvastatin dissolved in D2O is recorded. Predict the number of hydrogen atoms that would not show a peak in this spectrum. Explain your answer. …… [2] Table 5.1 chemical shift range environment of proton example δ / ppm alkane –CH3, –CH2–, >CH– 0.9–1.7 alkyl next to C=O CH3–C=O, –CH2–C=O, >CH–C=O 2.2–3.0 alkyl next to aromatic ring CH3–Ar, –CH2–Ar, >CH–Ar 2.3–3.0 alkyl next to electronegative atom CH3–O, –CH2–O, –CH2–Cl 3.2–4.0 attached to alkene =CHR 4.5–6.0 attached to aromatic ring H–Ar 6.0–9.0 aldehyde HCOR 9.3–10.5 alcohol ROH 0.5–6.0 phenol Ar–OH 4.5–7.0 carboxylic acid RCOOH 9.0–13.0 alkyl amine R–NH– 1.0–5.0 aryl amine Ar–NH2 3.0–6.0 amide RCONHR 5.0–12.0 (c) Atorvastatin reacts with an excess of LiAl H4. Name all the functional groups in atorvastatin that react with LiAl H4. Name the new functional group that would be formed in each case. names of functional groups in atorvastatin that react names of the new functional groups formed [2] [Total: 10]

Question

(a) A list of tests for different organic groups is given in Table 6.1. Complete Table 6.1 to identify an organic functional group, in aliphatic compounds, that produces a positive result in each test. Table 6.1 test I2(aq) warm with sodium Na2CO3(aq) 2,4-DNPH + Fehling’s Br2(aq) metal OH–(aq) reagent [4] (b) Lavandulol is an aliphatic organic compound and the major component of lavender oil. Fig. 6.1 shows a reaction scheme involving lavandulol, A. lavandulol, A (C10H18O) B (C10H16O) heat with concentrated acidified KMnO4 C (C6H8O5) D (C3H6O) + + CO2 NaBH4 E (C6H10O5) F (C6H8O4) heat with concentrated H2SO4 heat with concentrated acidified KMnO4 G (C4H4O5) H (C2H4O2) + Fig. 6.1 Table 6.2 shows the results obtained when the tests in Table 6.1 are carried out on the eight organic compounds, A–H, in the reaction scheme in Fig. 6.1. Table 6.2 test letter of I2(aq) warm with compound sodium Na2CO3(aq) 2,4-DNPH + Fehling’s Br2(aq) metal OH–(aq) reagent A 3 ✗ ✗ ✗ ✗ 3 B ✗ ✗ 3 ✗ 3 3 C 3 3 3 3 ✗ ✗ D ✗ ✗ 3 3 ✗ ✗ E 3 3 ✗ 3 ✗ ✗ F 3 3 ✗ ✗ ✗ 3 G 3 3 3 ✗ ✗ ✗ H 3 3 ✗ ✗ ✗ ✗ (i) Deduce the functional group present in compound A using both the molecular formulae of A and B and the reaction of B with Fehling’s reagent. …… [1] (ii) Name the type of reaction that occurs in each of the following conversions. • A B …… • C E …… • E F …… [3] (iii) Use the information in Table 6.2 and the molecular formulae to deduce structures for G and H. Draw your structures in Fig. 6.1. [2] (iv) Use the information in Table 6.2, the molecular formulae and your answer to (b)(iii) to deduce structures for A, C, D, E and F. Draw your structures in Fig. 6.1. [5] [Total: 15]

Question

(a) State the relative acidities of benzoic acid, C6H5COOH, ethanol, CH3CH2OH, and phenol, C6H5OH, in aqueous solution. Explain your answer. most acidic least acidic [3] (b) Draw the major products from the nitration of benzoic acid and phenol in the boxes in Fig. 7.1. The molecular formula for each major product is given in the boxes. major product from benzoic acid, C7H5NO4 major product from phenol, C6H5NO3 [2] Fig. 7.1 (c) Ethanol reacts with propanoyl chloride, C2H5COCl, to form ester W. W O O Fig. 7.2 (i) Give the systematic name for ester W. …… [1] (ii) Complete the mechanism in Fig. 7.3 for the reaction between C2H5COCl and ethanol. R–OH represents ethanol. Include all relevant lone pairs of electrons, curly arrows, charges and partial charges. organic intermediate O C 2H5 C products Cl R O H Fig. 7.3 [4] (iii) Name the mechanism for the reaction shown in Fig. 7.3. …… [1] [Total: 11]

Question

(a) (i) Define lattice energy, ΔHlatt. …… [2] (ii) Define enthalpy change of solution, ΔHsol. …… [1] (b) The enthalpy change of hydration can be represented by ΔHhyd. Write the mathematical expression for the ΔHsol of NaCl in terms of ΔHlatt(NaCl ), ΔHhyd(Na+) and ΔHhyd(Cl –). ΔHsol(NaCl ) = …… [1] (c) Complete the Born–Haber cycle in Fig. 8.1 for the ionic solid NaCl. Include state symbols of relevant species. ΔHea1 Na+(g) + Cl –(g) ΔHi1 ΔHat ΔHat ΔHf NaCl (s) Key ΔHi1 first ionisation energy ΔHea1 first electron affinity Fig. 8.1 [3] (d) Predict which of the ions, Cl – or NO3–, has the more negative enthalpy change of hydration. Explain your answer. …… [2] [Total: 9] Important values, constants and standards molar gas constant R = 8.31 J K–1 mol–1 Faraday constant F = 9.65 × 104 C mol–1 Avogadro constant L = 6.02 × 1023 mol–1 electronic charge e = –1.60 × 10–19 C molar volume of gas Vm = 22.4 dm3 mol–1 at s.t.p. (101 kPa and 273 K) Vm = 24.0 dm3 mol–1 at room conditions ionic product of water Kw = 1.00 × 10–14 mol2 dm–6 (at 298 K (25 °C)) specific heat capacity of water c = 4.18 kJ kg–1 K–1 (4.18 J g–1 K–1) The Periodic Table of Elements Group 1 2 13 14 15 16 17 18 1 2 H He hydrogen helium Key 1.0 4.0 3 4 atomic number 5 6 7 8 9 10 Li Be atomic symbol B C N O F Ne lithium beryllium name boron carbon nitrogen oxygen fluorine neon 6.9 9.0 relative atomic mass 10.8 12.0 14.0 16.0 19.0 20.2 11 12 13 14 15 16 17 18 Na Mg Al Si P S Cl Ar sodium magnesium aluminium silicon phosphorus sulfur chlorine argon 23.0 24.3 3 4 5 6 7 8 9 10 11 12 27.0 28.1 31.0 32.1 35.5 39.9 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 at www.cambridgeinternational.org after the live examination series. K Ca Sc Ti V Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr potassium calcium scandium titanium vanadium chromium manganese iron cobalt nickel copper zinc gallium germanium arsenic selenium bromine krypton 39.1 40.1 45.0 47.9 50.9 52.0 54.9 55.8 58.9 58.7 63.5 65.4 69.7 72.6 74.9 79.0 79.9 83.8 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 24 Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe rubidium strontium yttrium zirconium niobium molybdenum technetium ruthenium rhodium palladium silver cadmium indium tin antimony tellurium iodine xenon 85.5 87.6 88.9 91.2 92.9 95.9 – 101.1 102.9 106.4 107.9 112.4 114.8 118.7 121.8 127.6 126.9 131.3 55 56 57–71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 lanthanoids Cs Ba Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po At Rn caesium barium hafnium tantalum tungsten rhenium osmium iridium platinum gold mercury thallium lead bismuth polonium astatine radon 132.9 137.3 178.5 180.9 183.8 186.2 190.2 192.2 195.1 197.0 200.6 204.4 207.2 209.0 – – – 87 88 89–103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 actinoids Fr Ra Rf Db Sg Bh Hs Mt Ds Rg Cn Nh Fl Mc Lv Ts Og francium radium rutherfordium dubnium seaborgium bohrium hassium meitnerium darmstadtium roentgenium copernicium nihonium flerovium moscovium livermorium tennessine oganesson – – – – – – – – – – – – – – – – – 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 lanthanoids La Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu lanthanum cerium praseodymium neodymium promethium samarium europium gadolinium terbium dysprosium holmium erbium thulium ytterbium lutetium 138.9 140.1 140.9 144.2 – 150.4 152.0 157.3 158.9 162.5 164.9 167.3 168.9 173.1 175.0 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 actinoids Ac Th Pa U Np Pu Am Cm Bk Cf Es Fm Md No Lr actinium thorium protactinium uranium neptunium plutonium americium curium berkelium californium einsteinium fermium mendelevium nobelium lawrencium – 232.0 231.0 238.0 – – – – – – – – – – – Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge