Chemistry 2025 Oct/Nov | Past Paper

Q1

Short Answer 1 mark

Magnesium nitrate, Mg(NO , and strontium nitrate, Sr(NO , both decompose when heated to form the metal oxide and a mixture of gases.

Q1(a)

Short Answer 1 mark

Write an equation for the thermal decomposition of Mg(NO

Q1(b)

Short Answer 2 marks

State which of Mg(NO or Sr(NO decomposes at a lower temperature. Explain your answer . compound that decomposes at a lower temperature explanation

Q1(c)

Short Answer 1 mark

Magnesium oxide, MgO, and strontium oxide, SrO, both react with dilute sulfuric acid. MgO forms a soluble salt, A. SrO forms an insoluble salt, B.

Q1(i)

Short Answer 1 mark

Identify the products formed when MgO reacts with dilute sulfuric acid.

Q1(ii)

Short Answer 1 mark

Explain why A is more soluble than B. [Total: 7] * 0000800000003 * 2 Ethanal, CH CHO, reacts with nitrogen dioxide, NO . The products of the first step of this reaction are a CH =O radical and a molecule of nitrous acid, HNO CHO + NO =O + HNO

Q1(a)

Short Answer 1 mark

(i) Use two words to complete the sentence. This reaction involves of the single covalent bond between a hydrogen atom and a carbon atom in CH CHO.

Q1(ii)

Short Answer 1 mark

The hydrogen atom mentioned in (a)(i) forms a covalent bond with one of the oxygen atoms of an NO molecule. An NO molecule has a single, unpaired electron on the nitrogen atom. All electrons are paired in an HNO molecule. Draw dot-and-cross diagrams of NO and HNO in the boxes. Show outer shell electrons only. HNO

Q1(iii)

Short Answer 1 mark

Use VSEPR theory to predict the bond angle at the nitrogen atom in an HNO molecule. bond angle =

Q1(b)

Short Answer 1 mark

The rate equation for the reaction between CH CHO and NO is shown. rate = k [CH CHO][NO Under certain conditions, when the concentrations of both CH CHO and NO are 0.200 mol dm the rate of the reaction is 1.53 × 10 mol dm Calculate the value of the rate constant, k, under these conditions. Give the units of k. k = units [2] * 0000800000004 *

Q1(c)

Short Answer 1 mark

The reaction mixture described in

Q1(c)(b)

Short Answer 1 mark

is monitored over a period of time. Predict whether the graph of [NO ] against time shows a constant half-life. Explain your answer . prediction explanation

Q1(d)

Short Answer 1 mark

NO also reacts with ozone, O The rate equation is shown. rate = k [NO Under certain conditions, the value of k is 0.0848 s The reaction has a constant half-life under these conditions. Calculate the half-life in seconds. half-life = s

Q1(e)

Short Answer 1 mark

NO is present in the exhaust gases of cars. It can react with carbon monoxide, CO, on the surface of a heterogeneous catalyst in the car's catalytic converter. Describe the mode of action of this heterogeneous catalyst. [Total: 9] * 0000800000005 *

Q3(a)

Short Answer 1 mark

(i) Define conjugate acid-base pair.

Q3(ii)

Short Answer 1 mark

Give the formulas of the conjugate acid and the conjugate base of the hydrogen phosphate ion, HPO conjugate acid of HPO conjugate base of HPO

Q3(b)

Short Answer 1 mark

The K of propanoic acid, CH COOH, is 1.35 × 10 mol dm at 298 K. Solution C is a solution of CH COOH with a pH of 3.60 at 298 K.

Q3(i)

Short Answer 2 marks

Calculate the concentration of CH COOH in solution C. [CH COOH] = mol dm

Q3(ii)

Short Answer 1 mark

Calculate the concentration of hydroxide ions in solution C. [OH ] = mol dm

Q3(iii)

Short Answer 1 mark

Calculate the concentration of a solution of hydrochloric acid with the same pH as solution C. concentration = m ol dm [1] * 0000800000006 *

Q3(iv)

Short Answer 1 mark

Table 3.1 shows three possible values of the K of dimethylpropanoic acid, (CH CCOOH. Place a tick in Table 3.1 to show the correct value. Explain your answer. Table 3.1 value of K / mol dm in this column 9.33 × 10 1.35 × 10 3.35 × 10 explanation

Q3(c)

Short Answer 1 mark

Solution D is made by mixing 100 cm of 0.100 mol dm COOH and 100 cm 0.100 mol dm NaCl. The pH of solution D is measured as small amounts of H

Q3(aq)

Short Answer 1 mark

are added to it, and when small amounts of NaOH(aq) are added to it. Solution D only acts as a buf fer solution when one of these solutions is added to it.

Q3(i)

Short Answer 1 mark

Complete the sentence and write an equation for the reaction that occurs. Solution D acts as a buf fer when is added to it. equation

Q3(ii)

Short Answer 1 mark

Complete the sentence and explain why solution D does not act as a buf fer when the other solution is added. Solution D does not act as a buf fer when is added to it. explanation [1] * 0000800000007 *

Q3(d)

Short Answer 1 mark

Manganese(II) hydroxide, Mn(OH) , is only slightly soluble in water. The solubility of Mn(OH) in water is 3.28 × 10 g dm at 298 K.

Q3(i)

Short Answer 1 mark

Calculate the concentration of a saturated solution of Mn(OH) at 298 K. [Mn(OH) ] = mol dm

Q3(ii)

Short Answer 2 marks

Write an expression for the K of Mn(OH) . Give the units of K units =

Q3(iii)

Short Answer 1 mark

Use your answers to

Q3(iii)(ii)

Short Answer 1 mark

to calculate the value of K of Mn(OH) at 298 K. = [1] [Total: 15] * 0000800000008 *

Q4(a)

Short Answer 1 mark

Define enthalpy change of atomisation, ΔH

Q4(b)

Short Answer 1 mark

Define first electron affinity, EA.

Q4(c)

Short Answer 1 mark

Explain why the first electron af finity of chlorine is more exothermic than the first electron affinity of iodine.

Q4(d)

Short Answer 1 mark

The enthalpy change for the reaction Cl

Q4(g)

Short Answer 1 mark

+ 2e 2Cl

Q4(g)

Short Answer 1 mark

is - 486 kJ mol The first electron af finity of chlorine is -364 kJ mol Calculate the enthalpy change of atomisation of chlorine. of chlorine = kJ mol [2] [Total: 6] * 0000800000009 *

Q5

Short Answer 1 mark

Cobalt is a transition element which forms compounds containing Co and Co ions. Cobalt(II) sulfate dissolves in water to form a solution containing the [Co(H complex ion.

Q5(a)

Short Answer 1 mark

(i) Complete the electronic configurations of a Co ion and a Co ion. = [Ar] = [Ar]

Q5(ii)

Short Answer 1 mark

Explain why transition elements can form complex ions.

Q5(iii)

Short Answer 2 marks

An excess of concentrated HCl is added to a solution containing [Co(H Describe the colour change observed and the state of the cobalt-containing product. The colour changes from to . The state of the cobalt-containing product is .

Q5(iv)

Short Answer 1 mark

Write an equation for the reaction occurring in (a)(iii).

Q5(v)

Short Answer 1 mark

Name the type of reaction occurring in (a)(iii).

Q5(vi)

Short Answer 1 mark

Write an equation for the reaction that occurs when an excess of NaOH(aq) is added to a solution containing [Co(H [ i

Q5(b)

Short Answer 1 mark

Cobalt metal can be oxidised by acidified K . The relevant half-equations, and their values, are shown. + 2e Co E = -0.28 V + 14H + 6e 2Cr + 7HO E = +1.33 V

Q5(i)

Short Answer 2 marks

A Co /Co electrode is constructed in which [Co ] is 0.020 mol dm at 298 K. Use the Nernst equation to show that the E value for this Co / Co electrode is -0.33 V .

Q5(ii)

Short Answer 1 mark

An electrochemical cell is constructed using the Co / Co electrode described in (b)(i) and a Cr / Cr electrode in which all conditions are standard. Calculate the value of E cell cell =

Q5(iii)

Short Answer 1 mark

A current is drawn from the electrochemical cell described in (b)(ii). Write an equation for the reaction taking place in the cell.

Q5(iv)

Short Answer 1 mark

Complete the sentences to identify the negative electrode and the direction of electron flow when a current is drawn from the cell described in (b)(ii). The electrode is the negative electrode. Electrons flow from the electrode to the electrode.

Q5(c)

Short Answer 1 mark

A molten Co salt is electrolysed using a current of 0.500 A. 0.547 g of cobalt metal forms at the cathode. Under the conditions used no other reduction reaction occurs at the cathode. Calculate the time in minutes for which the current flows to produce this mass of cobalt. Give your answer to three significant figures. time = min [3] [Total: 15] * 0000800000011 * [[i

Q6(a)

Short Answer 1 mark

Nickel forms complexes.

Q6(i)

Short Answer 1 mark

Give the formula and charge of the tetrahedral complex formed by Ni atoms with carbon monoxide molecules. Carbon monoxide is a monodentate ligand. This is complex E. E =

Q6(ii)

Short Answer 2 marks

Give the formula and charge of the octahedral complex formed by Ni ions with ethanedioate ions. This is complex F. F =

Q6(iii)

Short Answer 1 mark

Identify which complex, E or F, ex ists as a mixture of two stereoisomers and the type of stereoisomerism involved. The complex which exists as a mixture of two stereoisomers is . The type of stereoisomerism involved is .

Q6(b)

Short Answer 1 mark

Cadmium forms complexes with methylamine, CH , and 1,2-diaminoethane, en. The values of the stability constants, K stab , of these complex ions are given in Table 6.1. Table 6.1 complex K stab [Cd(CH 3.5 × 10 [Cd(en) 4.0 × 10

Q6(i)

Short Answer 1 mark

Explain, by reference to its structure, why CH acts as a monodentate ligand.

Q6(ii)

Short Answer 1 mark

Some Cd

Q6(aq)

Short Answer 1 mark

is added to a solution containing equal concentrations of CH and en. Predict which of the two complexes in Table 6.1 forms at the higher concentration. Explain your answer. complex that forms at the higher concentration explanation

Q6(iii)

Short Answer 1 mark

Complete the expression for the K stab of [Cd(CH stab [1] [Total: 7] * 0000800000012 * [Ti

Q7

Short Answer 1 mark

P, Q, R, S, T, U, and V are the seven structural isomers with molecular form ula C O that have a carbonyl group. P CH (CH CHO Q CH CH(CH )CHO R (CH CHCHCHO S (CH CCHO T CH COCH U CH COCH V (CH CHCOCH

Q7(a)

Short Answer 2 marks

Only one of these seven compounds has stereoisomers. Draw three-dimensional diagrams of the two stereoisomers of this compound.

Q7(b)

Short Answer 1 mark

P, Q, R, S, T, U, and V are treated separately with alkaline I

Q7(aq)

Short Answer 1 mark

and the product mixture is acidified.

Q7(i)

Short Answer 1 mark

Identify the two compounds that give a positive result with alkaline I

Q7(ii)

Short Answer 1 mark

Describe the observations when one of the compounds you have identified in (b)(i) is treated with alkaline I

Q7(aq)

Short Answer 1 mark

and give the structural formulae of the two carbon-containing products of this reaction. observations two carbon-containing products and [2] * 0000800000013 * [ui P CH (CH CHO Q CH CH(CH )CHO R (CH CHCHCHO S (CH CCHO T CH COCH U CH COCH V (CH CHCOCH

Q7(c)

Short Answer 1 mark

The proton ( H) NMR spectra of P, Q, R, S, T, U, and V are compared.

Q7(i)

Short Answer 1 mark

Identify the only compound that gives a spectrum with two singlets and no other peaks. Fig. 7.1 shows the spectrum obtained from one of the compounds. 11 10 9 8 7 6 5 4 3 2 1 0 δ / ppm

Q7(ii)

Short Answer 1 mark

Identify the compound that gives this spectrum.

Q7(iii)

Short Answer 1 mark

Name the splitting pattern of the peak at δ = 1.1 in Fig. 7.1. Give the reason for this splitting. name reason

Q7(iv)

Short Answer 1 mark

Identify the substance that gives the small peak at δ = 0 in Fig. 7.1. [ri

Q7(d)

Short Answer 1 mark

The carbon-13 NMR spectra of R, S, T and U are compared. Complete Table 7.1 to state the number of peaks in the spectrum of each compound. Table 7.1 compound number of peaks R (CH CHCHCHO S (CH CCHO T CH COCH U CH COCH [2] [Total: 11] * 0000800000015 * [ni

Q8

Short Answer 1 mark

Asparagine and aspartic acid are two naturally occurring amino acids. Their structures and isoelectric points are shown in Table 8.1. Table 8.1 amino acid structure isoelectric point)CH CONH 5.41)CH COOH 2.77

Q8(a)

Short Answer 1 mark

Define isoelectric point.

Q8(b)

Short Answer 2 marks

Draw the structures of asparagine and aspartic acid at pH 2.

Q8(c)

Short Answer 1 mark

Asparagine and aspartic acid are treated separately with an ex cess of LiAl H Draw the structures of the organic products of these reactions. product of asparagine treated with an excess of LiAl H product of aspartic acid treated with an excess of LiAl H [2] * 0000800000016 * [oi

Q8(d)

Short Answer 1 mark

Propanedioic acid, HOOCCH COOH, is treated with an excess of thionyl chloride, SOCl Propanedioyl chloride, Cl OCCH COCl , is formed.

Q8(i)

Short Answer 1 mark

Write an equation for this reaction.

Q8(ii)

Short Answer 2 marks

Propanedioyl chloride reacts with an ex cess of asparagine to form compound G with molecular formula C Each molecule of compound G has four amide groups. Draw the structure of compound G. Compound G, C

Q8(e)

Short Answer 2 marks

Asparagine is hydrolysed with an excess of hot NaOH(aq). Draw the structure of the organic product of this reaction.

Q8(f)

Short Answer 1 mark

A polymer can form from asparagine, HOOCCH(NH)CH CONH , as the only monomer. Draw a length of the polymer chain containing three monomer residues. Clearly label the repeat unit of the polymer on your diagram. [3] * 0000800000017 * [vi

Q8(g)

Short Answer 1 mark

Aspartic acid exists in two optically active forms.

Q8(i)

Short Answer 2 marks

Plane polarised light is passed through pure samples of these two optically active forms in solutions of the same concentration. Describe two similarities and one dif ference in their effect on the plane polarised light. similarities difference

Q8(ii)

Short Answer 1 mark

Give the term used to describe a mixture of equal amounts of the two optically active forms. [Total: 16] * 0000800000018 * [ei Question 9 starts on page 20. * 0000800000019 * [Ci

Q9

Short Answer 1 mark

Compound X is made from benzene by the route shown in Fig. 9.1. step 1 step 2 step 3 COOH step 4 COOH benzene

Q9(a)

Short Answer 1 mark

Describe the bonding in benzene, C Y our answer should include: hydrogen atoms.

Q9(b)

Short Answer 1 mark

Describe the reagents and conditions required for step 1 in Fig. 9.1. T i

Q9(c)

Short Answer 3 marks

In step 1 of Fig. 9.1 benzene reacts with Complete Fig. 9.2 to show the mechanism for this reaction, including: 3 CH intermediate +

Q9(d)

Short Answer 1 mark

Describe the reagents and conditions required for step 2 of Fig. 9.1.

Q9(e)

Short Answer 1 mark

Identify the reagents required for step 3 of Fig. 9.1. Compound W is the product of this step.

Q9(f)

Short Answer 1 mark

Name compound W.

Q9(g)

Short Answer 1 mark

The reagents commonly used for step 4 will not reduce the -COOH group. Identify the reagents and conditions required for step 4 of Fig. 9.1. T[i

Q9(h)

Short Answer 1 mark

Benzene can also be used as a starting material to make compound Y. COOH compound Y Describe how the route described in Fig. 9.1 (repeated below) can be changed to give compound Y instead of compound X. Explain your answer . step 1 step 2 step 3 COOH step 4 COOH benzene [Total: 14] * 0000800000022 * TTi 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 * Tui 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 * Tri

Board	CAIE
Level	A Level
Subject	Chemistry
Code	`9701`
Year	2025
Session	Oct/Nov
Q&A	92 questions

Chemistry 2025 · Oct/Nov

Questions & Model Answers 92 Qs

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