Chemistry 2020 May/June | Past Paper

Q1

Short Answer 1 mark

FA 1 is an aqueous solution of a monoprotic organic acid. You will investigate the identity of FA 1 by using a titration method to find its relative molecular mass, M of a monoprotic organic acid. sodium hydroxide, NaOH. thymol blue indicator

Q1(a)

Short Answer 1 mark

Method of FA 1 into a conical flask. The rough titre is cm in each accurate titration. [7]IIIVII

Q1(b)

Short Answer 1 mark

From your accurate titration results, obtain a suitable value to be used in your calculations. Show clearly how you obtained this value. of FA 1 required cm of FA 2.

Q1(c)

Short Answer 1 mark

Calculations

Q1(i)

Short Answer 1 mark

Calculate the number of moles of sodium hydroxide present in the volume of FA 2 calculated in

Q1(i)(b)

Short Answer 1 mark

. moles of NaOH = mol [1] of FA 1. moles of organic acid = mol , of the organic acid in FA 1. Show your working.

Q1(iii)

Short Answer 1 mark

Calculate the relative molecular mass, M , of the organic acid in FA 1. of the organic acid =

Q1(iv)

Short Answer 1 mark

From another experiment it is found that FA 1 contains one of the following. COOH HCOOH CHCOOH NaOH(aq) reacts only with the COOH group in the acid. Deduce which of these acids is present in FA 1. Explain your answer.

Q1(d)

Short Answer 1 mark

This method of investigation uses the relative molecular mass of the acid. The relative molecular masses of C COOH and CH CHCOOH are similar so that any inaccuracy in the practical procedure could lead to an incorrect conclusion. Suggest a chemical test that would enable you to distinguish between C COOH and CHCOOH. Include the test and the results expected but do not carry out this test.

Q1(e)

Short Answer 1 mark

A student is given a solution of another organic acid containing the same concentration, in , as that used in

Q1(e)(a)

Short Answer 1 mark

. The student assumes this acid is monoprotic but it is diprotic. Explain the effect the student's assumption has on the value of the relative molecular mass that the student calculates. [Total 15]

Q2

Short Answer 1 mark

When an organic acid, RCOOH, is neutralised by an alkali an exothermic reaction takes place. You will determine the enthalpy change of neutralisation, ΔH, for the following reaction. RCOOH(aq) + NaOH(aq) RCOONa(aq) + H O

Q2(l)

Short Answer 1 mark

In this equation R is an alkyl group. of RCOOH. FA 4 is aqueous sodium hydroxide, NaOH.

Q2(a)

Structured 4 marks

Method Experiment 1 beaker. of FA 3 into the cup. measuring cylinder. thermometer. highest temperature reached. highest temperature reached. Experiment 2 measuring cylinder twice to measure the FA 3. highest temperature reached.

Q2(b)

Short Answer 1 mark

Calculations

Q2(i)

Short Answer 1 mark

Calculate the energy released in Experiment 1. energy released = J

Q2(ii)

Short Answer 2 marks

Calculate the number of moles of RCOOH used in Experiment 1. Assume that the relative molecular mass, M , of RCOOH is 122. Show your working. moles of RCOOH = mol

Q2(iii)

Short Answer 2 marks

Calculate the enthalpy change of neutralisation, ΔH, of RCOOH. Assume that the sodium hydroxide is in excess. enthalpy change of neutralisation of RCOOH = kJ sign value [1] Calculate the total maximum percentage error in the volumes of solution measured in each of Experiments 1 and 2. Experiment 1 total maximum percentage error = % Experiment 2 total maximum percentage error = %

Q2(d)

Short Answer 1 mark

A student repeated both experiments in

Q2(d)(a)

Short Answer 1 mark

using hydrochloric acid in place of RCOOH. Suggest how the temperature rise when using HCl would compare to the temperature rise , are the same. Explain your answer by considering the chemical bonds involved. [Total: 12] Qualitative Analysis Where reagents are selected for use in a test, the name or correct formula of the element or compound must be given. At each stage of any test you are to record details of the following: You should indicate clearly at what stage in a test a change occurs. If any solution is warmed, a boiling tube must be used. Rinse and reuse test-tubes and boiling tubes where possible. No additional tests for ions present should be attempted.

Q3

Short Answer 1 mark

Half fill the beaker with water and place it on a tripod and gauze. Heat until the water begins to boil then switch off your Bunsen burner. This is the hot water bath. add aqueous sodium hydroxide drop by drop until a small amount of brown precipitate is formed and then add aqueous ammonia drop by drop with shaking until the precipitate just dissolves. This is Tollens' reagent. When Tollens' reagent is used, ensure that all test-tubes are thoroughly rinsed immediately after use.

Q3(a)

Structured 5 marks

FA 5, FA 6 and FA 7 are organic compounds each of which contains carbon, hydrogen and oxygen only. test observations FA 5 FA 6 FA 7 Test 1 no visible reactionorange precipitate formed orange precipitate formed Test 2 magnesium ribbon. Test 3 place the tube in the hot water bath and leave for a few minutes. Test 4 Add a few drops of acidified potassium manganate( VII), place the tube in the hot water bath and leave for a few minutes.

Q3(ii)

Short Answer 3 marks

Identify the organic functional group present in each of FA 5, FA 6 and FA 7. FA 5 contains the functional group . FA 6 contains the functional group . FA 7 contains the functional group .

Q3(b)

Short Answer 1 mark

FA 8 contains one anion and one cation from those listed in the Qualitative Analysis Notes. strongly. Record all your observations.

Q3(ii)

Short Answer 3 marks

Describe tests that will allow you to identify the cation in FA 8. Carry out these tests and record the tests and your observations in the space below.

Q3(iii)

Short Answer 1 mark

Give the formula of the cation present in FA 8. [Total: 13] Qualitative Analysis Notes 1 Reactions of aqueous cationsion reaction with NaOH(aq) NH

Q3(aq)

Short Answer 1 mark

aluminium,

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

no ppt. ammonia produced on heating barium,

Q3(aq)

Short Answer 1 mark

faint white ppt. is nearly always observed unless reagents are pure no ppt. calcium,

Q3(aq)

Short Answer 1 mark

white ppt. with high [Ca

Q3(aq)

Short Answer 1 mark

] no ppt. chromium( III),

Q3(aq)

Short Answer 1 mark

grey-green ppt. soluble in excess grey-green ppt. insoluble in excess copper( II),

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

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,

Q3(aq)

Short Answer 1 mark

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

Q3(aq)

Short Answer 1 mark

gives white ppt. with Ag

Q3(aq)

Short Answer 1 mark

(soluble in NH

Q3(aq)

Short Answer 1 mark

) bromide,

Q3(aq)

Short Answer 1 mark

gives cream ppt. with Ag

Q3(aq)

Short Answer 1 mark

(partially soluble in NH

Q3(aq)

Short Answer 1 mark

) iodide,

Q3(aq)

Short Answer 1 mark

gives yellow ppt. with Ag

Q3(aq)

Short Answer 1 mark

(insoluble in NH

Q3(aq)

Short Answer 1 mark

) nitrate,

Q3(aq)

Short Answer 1 mark

liberated on heating with OH

Q3(aq)

Short Answer 1 mark

and Al foil nitrite,

Q3(aq)

Short Answer 1 mark

liberated on heating with OH

Q3(aq)

Short Answer 1 mark

and Al foil sulfate,

Q3(aq)

Short Answer 1 mark

gives white ppt. with Ba

Q3(aq)

Short Answer 1 mark

(insoluble in excess dilute strong acids) VXO?WH

Q3(aq)

Short Answer 1 mark

gives white ppt. with Ba

Q3(aq)

Short Answer 1 mark

(soluble in excess dilute strong acids) 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 (ppt. dissolves with excess CO chlorine, Cl bleaches damp litmus paper hydrogen, H ?pops? with a lighted splint oxygen, O relights a glowing splint 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 Table of Elements hydrogen 1.0 He helium 4.0 12131415161718 34567891011123Li 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 strontiu m 87.6 caesiu m 132. 9 barium137.3 franciu m radium boron 10.8 13 Al aluminium 27.0 31 Ga gallium 69.7 49 In indium 114.8 thallium204.4 carbon 12.0 14 Si silicon 28.1 32 Ge germanium 72.6 50 Sntin 118.7 82 Pb lead 207. 2 titanium 47.9 40 Zr zirconium 91.2 72 Hf hafnium 178. 5 rutherfordium vanadium 50.9 41 Nb niobium 92.9 73 Ta tantalum 180.9 105 Db dubnium chromium 52.0 42 Mo molybdenum 95.9 74 W tungste n 183. 8 106 Sg seaborgium manganese 54.9 43 Tc technetiu m rhenium 186. 2 107 Bh bohrium iron 55.8 44 Ru ruthenium 101.1 76 Os osmium 190.2 108 Hs hassium Co cobal t58.9 45 Rh rhodium 102.9 iridium192.2 109 Mt meitnerium nicke l58.7 46 Pd palladium 106. 4 platinum 195.1 110 Ds darmstadtiu m copper 63.5 47 Ag silver 107. 9 79 Au gold 197. 0 111 Rg roentgenium zinc 65.4 48 Cd cadmiu m 112.4 80 Hg mercury 200. 6 112 Cn copernicium fleroviu m livermorium nitrogen 14.0 phosphorus 31.0 33 As arseni c 74.9 51 Sb antimony 121. 8 bismuth 209. 0 oxygen 16.0 sulfur 32.1 34 Se selenium 79.0 52 Te tellurium 127.6 84 Po polonium fluorine 19.0 17 Cl chlorine 35.5 35 Br bromine 79.9 iodine 126.9 Ne neon 20.2 18 Ar argon 39.9 36 Kr krypto n 83.8 54 Xe xenon 131. 3 86 Rn radon scandium 45.0 yttriu m 88.9 57?71 lanthanoids 89?103 actinoids 57La lanthanum 138.9 89 Ac lanthanoids actinoids actinium Ce cerium 140.1 90 Th thoriu m232.0 praseodymium 140.9 91 Pa protactinium 231.0 neodymium 144.4 uranium 238.0 promethium neptunium samarium 150.4 94 Pu plutonium europium 152.0 95 Am americium gadolinium 157.3 96 Cm curium terbiu m158.9 97 Bk berkelium dysprosium 162.5 californium holmium 164.9 99 Es einsteinium erbium 167. 3 100 Fm fermium Tm thulium168. 9 101 Md mendelevium ytterbiu m 173. 1 102 No nobelium lutetium 175. 0 lawrencium

Board	CAIE
Level	A Level
Subject	Chemistry
Code	`9701`
Year	2020
Session	May/June
Q&A	56 questions

Chemistry 2020 · May/June

Questions & Model Answers 56 Qs

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