Chemistry 2025 May/June | Past Paper

Q1(a)

Short Answer 1 mark

(i) Calcium nitrate, Ca(NO , decomposes on heating. Write an equation for the decomposition of calcium nitrate.

Q1(ii)

Short Answer 1 mark

Describe the trend in the decomposition temperature of the Group 2 nitrates. Explain your answer.

Q1(b)

Short Answer 1 mark

A sample of 0.333 g of strontium oxide, SrO, is completely dissolved in distilled water to form a solution of strontium hydroxide, Sr(OH) The resulting solution is added to a volumetric flask and made up to 250.0 cm with distilled water. Calculate the pH of this solution at 298 K. Give your answer to two decimal places. pH = [4] [Total: 8] * 0000800000002 *

Q2(a)

Short Answer 1 mark

When cobalt(II) sulfate, CoSO , is dissolved in distilled water , solution A is formed. The reaction scheme in Fig. 2.1 shows some reactions of solution A. solution A solution Csolid B NaOH(aq) excess

Q2(aq)

Short Answer 1 mark

[CoCl

Q2(i)

Structured 4 marks

Complete Table 2.1 to show the formula and colour of each of the cobalt-containing species present in A, B and C. Identify the type of reaction forming each of B and C. Table 2.1 formula of cobalt-containing species colour of cobalt-containing species type of reaction

Q2(ii)

Short Answer 1 mark

Suggest a suitable reagent for the formation of [CoCl from solution A.

Q2(b)

Short Answer 1 mark

The complex ion [CoCl has tetrahedral geometry . The 3d orbitals in an isolated Co ion are degenerate.

Q2(i)

Short Answer 1 mark

Complete Fig. 2.2 to show the relative energies of the 3d orbitals in an isolated Coion and in Co in a tetrahedral complex. energy isolated Co ion Co in a tetrahedral complex [2] * 0000800000003 *

Q2(ii)

Short Answer 1 mark

Draw a three-dimensional diagram to show the structure of the complex ion [CoCl

Q2(c)

Short Answer 1 mark

H can act as an oxidising agent or a reducing agent when reacting with species that contain manganese. , for some electrode reactions. Table 2.2 / VMnO + 2H O + 2e Mn(OH) + 2OH -0.04MnO + 4H + 2e + 2H O +1.22 + 2H + 2e O +1.78 + OH + 2e 3OH +0.88 + 2H + 2e +0.68 Use only the species listed in Table 2.2 to suggest: acts as an oxidising agent and acts as a reducing agent. cell , and an overall equation for each reaction. acting as an oxidising agent acting as a reducing agent [4] * 0000800000004 *

Q2(d)

Short Answer 1 mark

Acidified manganate(VII) ions, MnO , can be used to analyse the content of iron tablets by titration. Tw o identical iron tablets are crushed and dissolved in distilled water . The resulting solution is made up to 150.0 cm with distilled water. 25.0 cm of this solution requires 18.60 cm of 0.0500 mol dm acidified MnO to reach the end-point. All the Fe ions are oxidised. The relevant half-equations are shown.MnO + 8H + 5e + 4H + e

Q2(i)

Short Answer 1 mark

Describe the colour change observed at the end-point of this titration. from to

Q2(ii)

Short Answer 1 mark

Calculate the mass, in mg, of iron in one tablet. Assume that all the iron in the tablets is Fe Show your working. mass of iron in one tablet = mg [4] [Total: 17] * 0000800000005 *

Q3(a)

Short Answer 1 mark

Define entropy.

Q3(b)

Short Answer 1 mark

Fig. 3.1 shows how the entropy, S, of a pure substance changes with temperature, T. temperature, T entropy, S

Q3(i)

Short Answer 1 mark

Identify the process occurring at each of the temperatures T and T is bigger than the entropy change at T

Q3(c)

Short Answer 1 mark

The equation for the reduction of iron(III) oxide by carbon monox ide at 450 °C is shown.

Q3(s)

Short Answer 1 mark

+ 3CO

Q3(s)(s)

Short Answer 1 mark

+ 3CO Table 3.1

Q3(s)

Short Answer 1 mark

CO(g) Fe(s) CO

Q3(g)

Short Answer 3 marks

f / kJ mol -824.2 -110.5 0.0 -393.5mol 87.4 to be calculated 27.3 213.8 Show your working. mol

Q3(d)

Short Answer 1 mark

Iron(II) oxide can also be reduced to iron by carbon monox ide, as shown. FeO

Q3(d)(s)

Short Answer 1 mark

+ CO mol State the ef fect of increasing temperature on the feasibility of this reaction. Explain your answer . [Total: 8] * 0000800000007 *

Q4(a)

Short Answer 1 mark

In aqueous solution, iodide ions react with acidified hydrogen peroxide, as shown in reaction 1. reaction 1 2I+ H + 2H + 2H The rate equation for reaction 1 is shown. rate = k [I][H

Q4(i)

Short Answer 1 mark

Explain what is meant by order of reaction.

Q4(ii)

Short Answer 2 marks

Complete T able 4.1. Table 4.1 the order of reaction with respect to [H the order of reaction with respect to [I the order of reaction with respect to [H overall order of the reaction

Q4(iii)

Short Answer 1 mark

Sketch a line on Fig. 4.1 to show the relationship between [I ] and time. time [1] * 0000800000008 *

Q4(b)

Short Answer 1 mark

Nitrogen dioxide, NO , reacts with ozone, O , as shown in reaction 2. reaction 2 2NO+ O + N The rate equation for reaction 2 is shown. rate = k [NO][O

Q4(i)

Short Answer 1 mark

Two experiments are carried out to measure the rate of reaction 2. In the first experiment, the initial rate is measured starting with known concentrations of NO and O . In the second experiment, the concentrations of NO and O are both increased by a factor of four. Predict how the initial rate for reaction 2 would change.

Q4(ii)

Short Answer 1 mark

The reaction mechanism for reaction 2 has two steps. Define rate-determining step.

Q4(iii)

Short Answer 1 mark

Suggest equations for the two steps of the reaction mechanism for reaction 2. step 1 step 2 [2] * 0000800000009 *

Q4(c)

Short Answer 1 mark

Dinitrogen pentoxide, N , can decompose to NO and O The rate equation for this decomposition is shown. rate = k [N Fig. 4.2 shows the graph of rate against [N ] for this decomposition. 0.0 0.00000.01000.02000.0300 ] / mol dm rate / 10 mol dm 0.04000.0500 2.0 4.0 6.0 12.0 14.0 16.0 8.0 10.0

Q4(i)

Short Answer 1 mark

Use Fig. 4.2 to calculate a value for the rate constant, k, for this decomposition. k = [1] , in seconds, for this decomposition. = s [1] [Total: 10] * 0000800000010 *

Q5(a)

Short Answer 1 mark

Chloric(I) acid, HCl O, is a weak Brønsted-Lowry acid. When chloric( I) acid is added to aqueous sodium hydroxide, an acid-base reaction takes place, as shown. HCl O + NaOH NaCl O + H

Q5(i)

Short Answer 1 mark

Identify the two conjugate acid-base pairs in this reaction. acid I HCl O conjugate base of acid I acid II conjugate base of acid II

Q5(ii)

Short Answer 2 marks

The value for the acid dissociation constant, K , of HCl O(aq) is 3.70 × 10 Calculate the concentration, in mol dm , of HCl O(aq) at a pH of 4.51. concentration of HCl O = mol dm

Q5(iii)

Short Answer 1 mark

When a solution of HCl O(aq) is heated, chloric( V) acid and a strong acid not containing oxygen are formed as the only products. Write an equation for this reaction.

Q5(b)

Short Answer 1 mark

(i) Define a buffer solution.

Q5(ii)

Short Answer 1 mark

Suggest a substance that could be added to aqueous ethanoic acid to form a buf fer solution. Explain your answer.

Q5(c)

Short Answer 2 marks

Some fertilisers contain calcium dihydrogenphosphate, Ca(H An aqueous solution containing dihydrogenphosphate ions, H , can act as a buf fer solution. W rite two equations to show how H ions can act as a buffer. equation 1 equation 2

Q5(d)

Short Answer 1 mark

The solubility of calcium phosphate, Ca (PO , is 1.14 × 10 mol dm at 25 °C.

Q5(i)

Short Answer 3 marks

The expression for the solubility product, K , of Ca (PO is shown. = [Ca [PO Calculate the value of K for Ca (PO . Include units. = units

Q5(ii)

Short Answer 1 mark

Some solid sodium phosphate is added to a saturated solution of Ca (PO Predict the effect, if any, on the solubility of Ca (PO Explain your answer. [Total: 12] * 0000800000012 *

Q6(a)

Short Answer 1 mark

Methylbenzene reacts readily with nitronium ions, NO ions are generated by the reaction between concentrated nitric acid and concentrated sulfuric acid.

Q6(i)

Short Answer 1 mark

Write an equation for the formation of the NO ion.

Q6(ii)

Short Answer 3 marks

Complete the mechanism in Fig. 6.1 for the nitration of methylbenzene to form 1-methyl-2-nitrobenzene. Include all relevant curly arrows and charges. organic intermediate 1-methyl-2-nitrobenzene +

Q6(b)

Short Answer 1 mark

Phenol can be nitrated with dilute nitric acid. Explain why the nitration of phenol occurs under milder conditions than the nitration of benzene.

Q6(c)

Short Answer 1 mark

A sample of 2-nitrophenol is reacted with sodium. Complete the equation in Fig. 6.2 for the reaction of 2-nitrophenol with sodium. +Na [1] * 0000800000013 *

Q6(d)

Short Answer 1 mark

2-nitrophenol can undergo different reactions as shown in Fig. 6.3. OH OH 2 CH COCl reaction 1 2-nitrophenol reaction 2

Q6(i)

Short Answer 1 mark

Suggest reagents and conditions for reaction 1.

Q6(ii)

Short Answer 1 mark

Name the type of reaction for reaction 1.

Q6(iii)

Short Answer 1 mark

Reaction 2 is carried out at room temperature. Draw the structure of the organic product from reaction 2 in Fig. 6.3.

Q6(iv)

Short Answer 1 mark

Name the mechanism for reaction 2.

Q6(e)

Short Answer 1 mark

The NO group in 2-nitrophenol is electron withdrawing. Suggest the relative acidities of ethanol, 2-nitrophenol, phenol and water . Explain your answer . most acidic least acidic [4] * 0000800000014 *

Q6(f)

Short Answer 1 mark

Salbutamol is a pharmaceutical drug that contains a phenol functional group. salbutamol

Q6(i)

Short Answer 2 marks

Name and classify the three other functional groups in salbutamol in Table 6.1. Table 6.1 name of functional group classification of functional group

Q6(ii)

Short Answer 1 mark

Salbutamol reacts with Br

Q6(aq)

Short Answer 1 mark

to form organic product X. Draw the structure of X.

Q6(iii)

Short Answer 1 mark

Salbutamol reacts with an excess of SOCl to form organic product Y. The molecular formula of Y is CNO. Draw the structure of Y. [1] [Total: 19] * 0000800000015 *

Q7(a)

Short Answer 1 mark

2-aminobutane, CH CH(NH)CH , exists as a mixture of two enantiomers. Define enantiomers.

Q7(b)

Short Answer 1 mark

(i) Explain why an aqueous solution of 2-aminobutane has a pH greater than 7. Include an equation in your answer.

Q7(ii)

Short Answer 1 mark

A 0.10 mol dm solution of diethylamine, (CH NH, has a higher pH than a 0.10 mol dm solution of 2-aminobutane, CH CH(NH)CH Suggest why.

Q7(iii)

Short Answer 1 mark

(CH NH reacts with ethanoic acid, CH COOH. Complete the equation for this reaction. (CH NH + CH COOH

Q7(iv)

Short Answer 1 mark

(CH NH reacts with ethanoyl chloride, CH COCl. Complete the equation for this reaction. (CH NH + CH COCl

Q7(c)

Short Answer 1 mark

Table 7.1 shows monomers that can undergo polymerisation.

Q7(i)

Short Answer 1 mark

Complete T able 7.1. Table 7.1 monomer type of polymerisation C(CH )COOH OHCl CH(NH )COOH

Q7(ii)

Short Answer 2 marks

Ethanedioic acid, HOOCCOOH, can react with propane-1,3-diamine, HNCH to form polymer W. Draw a section of polymer W showing only one repeat unit. The new functional group formed should be displayed.

Q7(iii)

Short Answer 1 mark

Poly(alkenes) biodegrade very slowly. Explain why. [Total: 11] * 0000800000017 *

Q8(a)

Short Answer 1 mark

Compound A is analysed by carbon-13 NMR and proton ( H) NMR spectroscopy. State the reference substance and a solvent that can be used in NMR spectroscopy . reference solvent

Q8(b)

Short Answer 1 mark

Predict the number of peaks in the carbon-13 NMR spectrum of A.

Q8(c)

Short Answer 1 mark

The proton ( H) NMR spectrum of A shows peaks in four dif ferent chemical environments. Complete Table 8.1 for the proton ( H) NMR spectrum of A. Table 8.1 chemical shift δ / ppm splitting pattern number of protons on adjacent carbon atoms number of H atoms responsible for the peak 1.10 1.50 6 2.85 3.75 [4] [Total: 6] * 0000800000018 * Table 8.2 environment of proton example chemical shift range δ / ppm alkane -CH , -CH -, >CH- 0.9-1.7 alkyl next to C=O CH -C=O, -CH -C=O, >CH-C=O 2.2-3.0 alkyl next to aromatic ring CH -Ar, -CH -Ar, >CH-Ar 2.3-3.0 alkyl next to electronegative atomCH -O, -CH -O, -CH -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-NH 3.0-6.0 amide RCONHR 5.0-12.0 * 0000800000019 *

Q9(a)

Short Answer 2 marks

The structures of the amino acids serine and lysine are shown in Fig. 9.1. serine lysine N COOHC N COOHC Draw the structure for the dipeptide, ser-lys, with molecular formula C The peptide functional group formed should be displayed.

Q9(b)

Short Answer 1 mark

The isoelectric point of serine is 5.7 and of lysine is 9.7.

Q9(i)

Short Answer 1 mark

State what is meant by isoelectric point.

Q9(ii)

Short Answer 1 mark

A mixture of serine, lysine and ser-lys is analysed by electrophoresis using a buf fer at pH 5.7. mixture applied here Draw and label three spots on Fig. 9.2 to indicate the predicted position of each of these three species, serine, lysine and ser-lys, after electrophoresis. Explain your answer.

Q9(c)

Short Answer 1 mark

Fig. 9.3 shows the synthesis of compound R from compound P. step 1 step 2 Q, C

Q9(i)

Short Answer 1 mark

Draw the structure of Q in Fig. 9.3.

Q9(ii)

Short Answer 1 mark

State the reagents and conditions for steps 1 and 2 in Fig. 9.3. step 1 step 2 [2] [Total: 9] * 0000800000021 * BLANK PAGE * 0000800000022 * Important values, constants and standards molar gas constant R = 8.31 J Kmol Faraday constant F = 9.65 × 10 C mol Avogadro constant L = 6.02 × 10mol electronic charge e = -1.60 × 10-19 molar volume of gas V = 22.4 dmmol at s.t.p. (101 kPa and 273 K) = 24.0 dmmol at room conditions ionic product of water K = 1.00 × 10-14mol (at 298 K (25 °C)) (4.18 J g ) * 0000800000023 * To avoid the issue of disclosure of answer-related information to candidates, all copyright acknowledgements are reproduced online in the Cambridge Assessment International Education Copyright Acknowledgements Booklet. This is produced for each series of examinations and is freely available to download at www.cambridgeinternational.org after the live examination series. Group The Periodic Ta ble of Elements hydrogen 1.0 helium 4.0 12 13 14 15 16 17 18 3456789 10 11 12 lithium 6.9 beryllium 9.0 atomic number atomic symbolKey name relative atomic mass sodium 23.0 magnesium 24.3 potassium 39.1 calcium 40.1 rubidium 85.5 strontium 87.6 caesium 132.9 barium 137.3 francium radium boron 10.8 aluminium 27.0 gallium 69.7 indium 114.8 thallium 204.4 carbon 12.0 silicon 28.1 germanium 72.6tin 118.7 lead 207.2 titanium 47.9 zirconium 91.2 hafnium 178.5 rutherfordium vanadium 50.9 niobium 92.9 tantalum 180.9 dubnium chromium 52.0 molybdenum 95.9 tungsten 183.8 seaborgium manganese 54.9 technetium rhenium 186.2 bohrium iron 55.8 ruthenium 101.1 osmium 190.2 hassium cobalt 58.9 rhodium 102.9 iridium 192.2 meitnerium nickel 58.7 palladium 106.4 platinum 195.1 darmstadtium copper 63.5 silver 107.9 gold 197.0 roentgenium zinc 65.4 cadmium 112.4 mercury 200.6 copernicium flerovium livermorium nitrogen 14.0 phosphorus 31.0 arsenic 74.9 antimony 121.8 bismuth 209.0 oxygen 16.0 sulfur 32.1 selenium 79.0 tellurium 127.6 polonium fluorine 19.0 chlorine 35.5 bromine 79.9 iodine 126.9 neon 20.2 argon 39.9 krypton 83.8 xenon 131.3 radon nihonium moscovium tennessine oganesson scandium 45.0 yttrium 88.9 57-71 lanthanoids 89-103 actinoids lanthanum 138.9 lanthanoids actinoids actinium cerium 140.1 thorium 232.0 praseodymium 140.9 protactinium 231.0 neodymium 144.2 uranium 238.0 promethium neptunium samarium 150.4 plutonium europium 152.0 americium gadolinium 157.3 curium terbium 158.9 berkelium dysprosium 162.5 californium holmium 164.9 einsteinium erbium 167.3 fermium thulium 168.9 mendelevium ytterbium 173.1 nobelium lutetium 175.0 lawrencium - * 0000800000024 *

Board	CAIE
Level	A Level
Subject	Chemistry
Code	`9701`
Year	2025
Session	May/June
Q&A	79 questions

Chemistry 2025 · May/June

Questions & Model Answers 79 Qs

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