Chemistry 2024 May/June | Past Paper

Q1

Short Answer 1 mark

When ammonium compounds are heated with sodium hydroxide or calcium hydroxide, ammonia is liberated. The ionic equation for the reaction is shown. + OH + H FA 1 is prepared by heating 10.0 cm of aqueous ammonium chloride, NH Cl (aq), with 25.0 cm 2.00 mol dm sodium hydroxide, NaOH. The sodium hydroxide is in ex cess. The reaction mixture is cooled and diluted to 250 cm with distilled water. You will determine the concentration of the aqueous solution of amm onium chloride by titrating the remaining sodium hydroxide from the preparation of FA 1 with a known concentration of sulfuric acid. 2NaOH(aq) + H

Q1(aq)

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+ 2H O

Q1(aq)(l)

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FA 2 is 0.0520 mol dm sulfuric acid, H FA 3 is bromophenol blue indicator .

Q1(a)

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Method of FA 1 into a conical flask. The rough titre is cm of FA 2 added in each accurate titration. Results [7]III VII * 0019656615802 *, ,

Q1(b)

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From your accurate titration results, calculate a suitable mean value to use in your calculations. Show clearly how you obtain the mean value. 25.0 cm of FA 1 required cm of FA 2.

Q1(c)

Short Answer 1 mark

Calculations

Q1(i)

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Give your answers to

Q1(i)(v)

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to an appropriate number of significant figures.

Q1(ii)

Short Answer 1 mark

Calculate the amount, in mol, of sulfuric acid present in the volume of FA 2 in

Q1(ii)(b)

Short Answer 1 mark

. amount of H = mol

Q1(iii)

Short Answer 1 mark

Use your answer to (c)(ii) to calculate the amount, in mol, of sodium hydroxide in 25.0 cm of FA 1. amount of NaOH = mol

Q1(iv)

Short Answer 2 marks

Use your answer to (c)(iii) and the information given to calculate the amount, in mol, of sodium hydroxide that reacted with the ammonium chloride when FA 1 was prepared. amount of NaOH that reacted with NH Cl = mol

Q1(v)

Short Answer 1 mark

Use your answer to (c)(iv) and the information given to calculate the concentration, in mol dm , of the ammonium chloride solution used to prepare FA 1. concentration of NH Cl = mol dm

Q1(d)

Short Answer 1 mark

When ammonia gas is prepared by heating one of its salts with calcium hydroxide, it can be dried by passing it through a drying agent. Drying agents for gases include calcium oxide, calcium sulfate, concentrated sulfuric acid and phosphorus(V) oxide. Select one of these drying agents and suggest why it is not suitable for drying amm onia gas. [Total: 15] * 0019656615803 *, ,

Q2

MCQ 1 mark

A sample of ammonium bromide has been accidentally mixed with another salt. A student suggests that the percentage purity of the ammonium bromide can be determined by measuring the change in temperature when a solution is prepared. The enthalpy change when the sample dissolves in water , ΔH, can then be calculated and compared with the literature value for ammonium bromide. You will carry out the student's experiment. FA 4 is ammonium bromide, NH Br, mixed with another salt.

A

sample of ammonium bromide has been accidentally mixed with another salt.

A

student suggests that the percentage purity of the ammonium bromide can be determined by

Q2(a)

Structured 4 marks

Method beaker. measuring cylinder to transfer 25.0 cm of distilled water into the cup. thermometer is fully covered. Record the temperature of the water in the space for results. Results

Q2(b)

Short Answer 1 mark

(i) Calculate the energy change, in J, for the reaction. energy change = J

Q2(ii)

Short Answer 1 mark

When one mole of ammonium brom ide dissolves in water the enthalpy change, ΔH, is +16.8 kJ mol Use this value to calculate the amount, in mol, of ammonium bromide in the 25.0 cm solution FA 4 used in your experiment. Assume that the enthalpy change when the other salt dissolves in water is 0 kJ mol amount of NH Br in 25.0 cm = mol [1]III IV * 0019656615804 *, ,

Q2(iii)

Short Answer 1 mark

Calculate the mass, in g, of ammonium bromide in your sample. (If you were unable to calculate the amount of ammonium bromide in (b)(ii), then assume it is 2.06 × 10 mol. This may not be the correct answer .) mass of NH Br in sample = g

Q2(iv)

Short Answer 1 mark

Hence calculate the percentage by mass of ammonium bromide in your sample. % by mass of NH Br = %

Q2(c)

Short Answer 1 mark

Another student states that this method is not accurate as the enthalpy change when the other salt dissolves in water could be exothermic. Suggest how the calculated value in (b)(iv) would change if the other salt dissolves in water exothermically. Explain your answer.

Q2(d)

Short Answer 1 mark

The maximum uncertainty in a single thermometer reading is ±0.5 ëC. Calculate the maximum percentage error in your temperature change recorded in

Q2(d)(a)

Short Answer 1 mark

. Show your working. maximum percentage error = % [1] [Total: 10] * 0019656615805 *, , Qualitative analysis For each test you should record all your observations in the spaces provided. Examples of observations include: added You should record clearly at what stage in a test an observation is made. Where no change is observed, you should write `no change'. Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. If any solution is warmed, a boiling tube must be used. If a solid is heated, a hard-glass test-tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests should be attempted.

Q3(a)

Short Answer 1 mark

FA 5 is a mixture containing two cations and two anions. Three of the ions are listed in the Qualitative analysis notes.

Q3(i)

Short Answer 1 mark

Carry out the following tests and record your observations in Table 3.1. Table 3.1 test observations Test 1 Heat a spatula measure of FA 5 in a hard-glass test-tube. Test 2 Put a 2 cm depth of dilute nitric acid in a boiling tube. Add a spatula measure of FA 5. Dilute the solution from Test 2 with an equal volume of distilled water. Keep the resulting solution for use in (a)(ii). This solution is FA 6. [3] * 0019656615806 *, ,

Q3(ii)

Short Answer 1 mark

Carry out the following tests using a 1 cm depth of FA 6 in a test-tube for each test. Record your observations in Table 3.2. Table 3.2 test observations Test 1 Add a 1 cm depth of sodium chlorate(I), then add aqueous sodium thiosulfate dropwise. Test 2 Add aqueous sodium hydroxide. Test 3 Add aqueous ammonia. Test 4 Add a 1 cm depth of aqueous copper(II) sulfate, then add aqueous sodium thiosulfate dropwise until no further change occurs. Test 5 Add a few drops of aqueous silver nitrate, then add aqueous ammonia until no further change occurs. [4] * 0019656615907 *

Q3(iii)

Short Answer 1 mark

FA 5 reacts with nitric acid to make FA 6 in Test 2 in Table 3.1. State a change you would see in one of the observations in Table 3.2 if hydrochloric acid had been used to prepare FA 6.

Q3(iv)

Short Answer 1 mark

Use your observations in

Q3(iv)(ii)

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to identify the formulae of three of the ions present in FA 5. Formulae of ions present are and and .

Q3(b)

Short Answer 1 mark

FA 7, FA 8 and FA 9 are each known to be propan-1-ol, propanal, propanoic acid or propanone. No two liquids are identical.

Q3(i)

Short Answer 1 mark

You will carry out tests to identify samples of FA 7, FA 8 and FA 9. Test 1 has been carried out for you. Carry out Test 2 and record your observations in Table 3.3. Table 3.3 test observations FA 7 FA 8 FA 9 Test 1 Put a 1 cm depth in a test- tube. Add a few drops of 2,4-dinitrophenylhydrazine (2,4-DNPH reagent). orange precipitateorange precipitate no change Test 2 Put a 1 cm depth in a test- tube. Add a small spatula measure of solid sodium carbonate.

Q3(ii)

Short Answer 1 mark

State what you can deduce from Tests 1 and 2 in Table 3.3 about the functional group present in each of FA 7, FA 8 and FA 9., ,

Q3(iii)

Short Answer 1 mark

Describe a test to identify FA 7 and FA 8 using the reagents provided. Carry out your test. Record your observations and conclusions. test observations FA 7 is . FA 8 is . [2] [Total: 15] * 0019656615909 * Qualitative analysis notes 1 Reactions of cations cation reaction with NaOH(aq) NH

Q3(aq)

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aluminium, Al

Q3(aq)

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white ppt. soluble in excess white ppt. insoluble in excess ammonium, NH

Q3(aq)

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no ppt. ammonia produced on warming barium, Ba

Q3(aq)

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faint white ppt. is observed unless [Ba

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] is very low no ppt. calcium, Ca

Q3(aq)

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white ppt. unless [Ca

Q3(aq)

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] is verylow no ppt. chromium(III), Cr

Q3(aq)

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grey-green ppt. soluble in excess giving dark green solution grey-green ppt. insoluble in excess copper(II), Cu

Q3(aq)

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pale blue ppt. insoluble in excesspale blue ppt. soluble in excess giving dark blue solution iron(II), Fe

Q3(aq)

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green ppt. turning brown on contact with air insoluble in excess green ppt. turning brown on contact with air insoluble in excess iron(III), Fe

Q3(aq)

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red-brown ppt. insoluble in excessred-brown ppt. insoluble in excess magnesium, Mg

Q3(aq)

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white ppt. insoluble in excesswhite ppt. insoluble in excess manganese(II),

Q3(aq)

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off-white ppt. rapidly turning brown on contact with air insoluble in excess off-white ppt. rapidly turning brown on contact with air insoluble in excess zinc, Zn

Q3(aq)

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white ppt. soluble in excess white ppt. soluble in excess 2 Reactions of anions anion reaction carbonate, CO liberated by dilute acids chloride, Cl

Q3(aq)

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gives white ppt. with Ag

Q3(aq)

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(soluble in NH

Q3(aq)

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) bromide, Br

Q3(aq)

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gives cream / off-white ppt. with Ag

Q3(aq)

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(partially soluble in NH

Q3(aq)

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) iodide, I

Q3(aq)

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gives pale yellow ppt. with Ag

Q3(aq)

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(insoluble in NH

Q3(aq)

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) nitrate, NO

Q3(aq)

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NH liberated on heating with OH

Q3(aq)

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and Al foil nitrite, NO

Q3(aq)

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NH liberated on heating with OH

Q3(aq)

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and Al foil; decolourises acidified aqueous KMnO sulfate, SO

Q3(aq)

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gives white ppt. with Ba

Q3(aq)

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(insoluble in excess dilute strong acids); gives white ppt. with high [Ca

Q3(aq)

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] sulfite, SO

Q3(aq)

Short Answer 1 mark

gives white ppt. with Ba

Q3(aq)

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(soluble in excess dilute strong acids); decolourises acidified aqueous KMnO thiosulfate, S

Q3(aq)

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gives off-white / pale yellow ppt. slowly with H + * 0019656615910 * 3 Tests for gases gas test and test result ammonia, NH turns damp red litmus paper blue carbon dioxide, CO gives a white ppt. with limewater hydrogen, H `pops' with a lighted splint oxygen, O relights a glowing splint

Q4

Short Answer 1 mark

Tests for elements element test and test result iodine, I gives blue-black colour on addition of starch solution Important values, constants and standards molar gas constant R = 8.31 J Kmol Faraday constant F = 9.65 × 10 C mol Avogadro constant L = 6.022 × 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)) specific heat capacity of waterc = 4.18 kJ kg (4.18 J g ) * 0019656615911 * 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 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. * 0019656615912 *

Board	CAIE
Level	A Level
Subject	Chemistry
Code	`9701`
Year	2024
Session	May/June
Q&A	67 questions

Chemistry 2024 · May/June

Questions & Model Answers 67 Qs

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