Understanding 2024 DSE Chemistry Paper 1B: Key Instructions and
School
The University of Hong Kong**We aren't endorsed by this school
Course
MATH 2011
Subject
Chemistry
Date
Dec 10, 2024
Pages
19
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2024-DSE CHEM PAPER 1B HONG KONG EXAMINATIONS AND ASSESSMENT AUTHORITY HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION 2024 CHEMISTRY PAPER 1 SECTION B: Question-Answer Book B This paper must be answered in English INSTRUCTIONS FOR SECTION B @} ) 3 ) (5) 6) @) After the announcement of the start of the examination, you should first write your Candidate Number in the space provided on Page 1 and stick barcode labels in the spaces provided on Pages 1, 3,5,7and9. Refer to the general instructions on the cover of the Question Paper for Section A. This section consists of TWO parts, Parts | and II. Answer ALL questions in both Parts | and Il. Write your answers in the spaces provided in this Question-Answer Book. Do not write in the margins. Answers written in the margins will not be marked. An asterisk (*) has been put next to the questions where one mark will be awarded for effective communication. Supplementary answer sheets will be pl%vided on request. Write your candidate number, mark the question number box and stick a barcode label on each sheet, and fasten them with string INSIDE this Question-Answer Book. No extra time will be given to candidates for sticking on the barcode labels or filling in the question number boxes after the ‘Time is up’ announcement. OFEFARNEE TREhR Hong Kong Examinations and Assessment Authority All Rights Reserved 2024 2024-DSE-CHEM 1B-1 1 Please stick the barcode label here. Candidate Number I
Answers written in the margins will not be marked. PART I Answer ALL questions. Write your answers in the spaces provided. (@) ®) ©) Carbon occurs naturally in two stable isotopes, 'C and C. (i) Give one difference between a '2C atom and a "°C atom. (1 mark) (i) The relative atomic mass of carbon is 12.011, Assuming that carbon only has two isotopes, 12C and 1°C, calculate the percentage abundance of 2C. (2 marks) Diamond and graphite are two different forms of carbon. Diamond is a poor conductor of electricity while graphite is a good conductor of electricity. State the similarity and difference of diamond and graphite in terms of bonding and structure. Hence, account for their difference in electrical conductivity. (3 marks) C2N; is a compound of carbon and nitrogen. It contains one carbon-carbon single bond. Draw the electron diagram for a C;Nz molecule, showing ELECTRONS IN THE OUTERMOST SHELLS only. (1 mark) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-2 2
Please stick the barcode label here. 25 An experiment was performed to investigate the rusting of iron with the set-ups shown below : glass dish iron nail wrapped with iron nail wrapped with metal X metal Y gel containing phenolphthalein and tassium hexacyanoferrate(Il! Set-up 1 L yen D Set-up 2 X, Y and iron are three different metals. After a period of time, a pink colour appeared in both set-up 1 and set-up 2, whereas a blue colour appeared around the iron nail in set-up 1 only. (a) State the essential conditions for the rusting of iron. (1 mark) 0) Suggest which species changed to pink colour in set-up 1 and set-up 2. (1 mark) ©) Explain why the blue colour appeared around the iron nail in set-up 1. Answers written in the margins will not be marked. Answers written in the margins will not be marked. [3 (2 marks) (d) Based on the above observations, arrange the three metals (X, Y and iron) in decreasing order of reactivity. Explain your answer. S S S (2 marks) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-3 BB o ittt bt it i
Answers written in the margins will not be marked. 1.0 M. The voltage of the cell is measured by an apparatus W. Cu(s) CuSO4(aq) — — AgNOs(aq) half cell A half cell B Chemical cell 1 (@) Suggest what apparatus W is. (b) Suggest one function of a salt bridge. (c) In preparing the salt bridge in chemical cell 1, @ explain why KCl(aq) cannot be used. (ii) suggest a suitable solution that can be used. 3. The diagram below shows the experimental set-up of a chemical cell. All the solutions used in the cell are (1 mark) (1 mark) (1 mark) (1 mark) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B—4 4 Answers written in the margins will not be marked.
Answers written in the margins will not be marked. Please stick the barcode label here. Three other experiments are conducted by using a set-up similar to chemical cell 1, but different o combinations of electrodes and 1.0 M solutions (CuSOa(aq), AgNOs(aq), ZnSO4(aq) and MnSO4(aq)) are used in the half cells. The table below shows the information of the chemical cells : Chemical cell Half cell A Half cell B Voltage/ V 1 Cu(s) / Cu?*(aq) Ag(s)/ Ag*(aq) —-0.46 2 Cu(s) / Cu**(aq) Zn(s) / Zn*(aq) +1.10 3 Cu(s) / Cu?*(aq) Mn(s) / Mn?*(aq) +1.15 4 Ag(s)/ Ag'(aq) Mn(s) / Mn**(aq) y (i) With reference to chemical cells 1, 2 and 3, state and explain which of the four metals used in the above chemical cells is the strongest reducing agent. (2 marks) (i) Calculate the expected value of y. Answers written in the margins will not be marked. (1 mark) (iii) Write the half equationsfor the change that occurs at the cathode of chemical cell 4. (1 mark) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-5 5
Answers written in the margins will not be marked. 4. Sulphamic acid (relative molecular mass = 97.1) can be used to remove limescale in water boilers. Limescale is mainly composed of CaCO;. (a) Sulphamic acid only contains 3.09% of hydrogen, 14.42% of nitrogen, 49.43% of oxygen and 33.06% of sulphur by mass. (i) Determine, by calculation, the empirical formula of sulphamic acid. (Relative atomic masses : H=1.0, N=14.0,0 = 16.0, S = 32.1) (2 marks) (ii) Deduce the molecular formula of sulphamic acid. (1 mark) (b) In an experiment, 0.486 g of sulphamic acid reacted with 100.0 cm® of 0.150 M NaOH(aq), which was in excess. The remaining NaOH(aq) required 24.80 cm® of 0.202 M H,SO4(aq) for complete neutralisation. (i) Calculate the number of moles of NaOH(aq) that reacted with the H>SOu(aq). (1 mark) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-6 6
Please stick the barcode label here. Answers written in the margins will not be marked. 4. ®) @) (1 mark) (iii) Deduce the basicity of sulphamic acid. k] 5 E 2 2 E E g - ] (1 mark) | g = () Write an ionic equation for the reaction between CaCOs(s) in limescale and H'(aq). 3§ g H 2 (1 mark) Calculate the number of moles of NaOH(aq) that reacted with the sulphamic acid. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-7 7
Answers written in the margins will not be marked. 5; Kerosene can be obtained from petroleum. (a) State a physical method to obtain kerosene from petroleum. Explain the underlying principle of this method. (2 marks) (b) The following diagram shows the experimental set-up of a chemical process done on kerosene. boiling tube broken unglazed porcelain vt W - heat occasionally heat strongly delivery tube [0 Name the chemical process that occurs in the boiling tube. (1 mark) (i) ‘Why should the deliveg tube be taken out of the water before removing the heat source ? (1 mark) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-8 8
Please stick the barcode label here. Answers written in the margins will not be marked. 5. (b) (iiiy Explain why the gas mixture collected can decolourise bromine water rapidly. (1 mark) (iv) If only the mineral wool with kerosene is heated strongly, but the broken unglazed porcelain is not heated, the chemical process in (b)(i) would not occur significantly. Suggest TWO reasons to explain why. (2 marks) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-9 9 Go on to the next page
Answers written i i ers n in the margins will not be marked. six solutions of 0.1 Mare put into tWO groups s follows * Na:COx(ad) FeSO«(aq) FeCls(aq) NH;(aq) Me(NO:)2(29) HaSO4(a0) up A is mixed with one solution from Group B One solution from Gro! (a) (i) Which TWO solutions can give a green precipitate on mixing ? (1 mark) (ii) Name the green precipitate mentioned in (a)(i)- (1 mark) (b) (i) Which TWO solutions can give a white precipitate on mixing ? (1 mark) hite precipitate mentioned in (b)(i)- (ii) Write an ionic equation for the formation of the W Answers Written € in th margins will not be marked, (1 mark) © Which TWO solutions can give off gas bubbles on mixing ? ® (1 mark) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-10 10
Answers written in the margins will not be marked. 7 (a) (i) Draw the three-dimensional structure of a dichloromethane molecule. (1 mark) (i) Explain whether the bonds in a dichloromethane molecule are polar. (2 marks) (iii) Explain whether a dichloromethane molecule is polar. (1 mark) (b) Explain why the boiling point of dichloromethane is lower than that of ethanol. <3 (2 marks) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-11 11 Answers written in the margins will not be marked.
Answers written in the margins will not be marked. 8. Five experiments were conducted to determine the enthalpy changes of neutralisation between different acids and alkalis as shown below. All experiments were performed by mixing 50.0 cm’ of 1.0 M acid with 50.0 cm’® of 1.0 M alkali at room conditions. Experiment Acid Alkali 1 HCl(aq) NaOH(aq) 2 HCl(aq) KOH(aq) 3 HNO;(aq) NaOH(aq) 4 HNO;(aq) KOH(aq) 5 CH3;COOH(aq) NaOH(aq) (a) In Experiment 1, the temperature of the reaction mixture was raised by 6.8 °C. Calculate the enthalpy change of neutralisation between HCI(aq) and NaOH(aq), in kJ mol™. (Density of the reaction mixture = 1.0 g cm™; specific heat capacity of the reaction mixture =4.20 J g™ K™') (2 marks) (b) Explain why the enthalpy changes of neutralisation found in experiments 1 to 4 were approximately the same. (1 mark) () The result of Experiment 5 showed that the enthalpy change of neutralisation between CH3;COOH(aq) and NaOH(aq) was —50.10 kJ mol™'. Using your answer to (a), calculate the enthalpy change for the following reaction. CH;COOH(aq) — CH;COO(aq) + H'(aq) (2 marks) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-12 12 Answers written in the margins will not be marked.
Answers written in the margins will not be marked. 29, Using silver oxide, lead(IT) oxide and aluminium oxide as examples, state THREE different methods to extract metals from their oxides, and describe the relation between the extraction method of a metal and its position in the metal reactivity series. (5 marks) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-13 13 Go on to the next page e ——
Answers written in the margins will not be marked. PART II Answer ALL questions. Write your answers in the spaces provided. 10. The decomposition of hydrogen peroxide is shown below : 2H,02(aq) - 2H,0(1) + 0(g) Four experiments were performed to compare the effects of four different solid catalysts A, B, C and D on the decomposition of hydrogen peroxide at room conditions. In each experiment, the same amount of the respective catalyst was added to 10.0 cm’ of 0.50 M H,0,(aq) and the decomposition was allowed to go to completion. The volumes of oxygen gas evolved were measured at regular time intervals. The graph below shows the results of the experiments in the first 35 seconds. 140 120 100 8 a 80 g s using-catalyst § 60 = - S = - us il{géaml st 40 m—— ”’ — < = using catalyst 74 = catalyst C 20 7 =TT 1~ 7 = o 1t T == using catalyst D 1] +—t 0— = L1 N 0 5 10 15 20 25 30 35 time /s Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-14 14
Answers written in the margins will not be marked. 10. (a) Complete the following set-up diagram (with label) to show how the volumes of oxygen gas formed can be measured in the above experiments. catalyst (1 mark) (b) Which of the four catalysts is the most effective ? Explain your answer. (1 mark) (©) What is the theoretical final volume of oxygen gas produced in the experiment using catalyst B ? (1 mark) @ A fifth experiment was conducted using the same amount of catalyst A, but 10.0 cm® of 1.00 M H;01(aq) was used. The reaction completed at the 20" second. Sketch a curve on the graph on page 14 to show the expected result in the first 35 seconds. (Molar volume of gas at room conditions =24 dm®) (2 marks) Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-15 15 Answers written in the margins will not be marked.
Answers written in the margins will not be marked. (@ (®) © @ (e OH Q AlLOs(s), heat —— > R 11 Refer to the following conversions involving five organic compounds P, Q, R, S and T. HCI (g) s + T (major product) (minor product) Suggest the reagent(s) and condition(s) needed for the conversion of P to Q. (1 mark) State the type of reaction involved in the conversion of Q to R. Draw the structure of R. Draw the structure of S. (1 mark) (1 mark) (1 mark) State which TWO of the four organic compounds, Q, R, S and T, can react with KMnOs(aq) under appropriate conditions, and draw the structures of the organic products formed respectively. Compound Compound Structure of organic product : Structure of organic product : (3 marks) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-16 16
Answers written in the margins will not be marked. 12 An organic compound Z can be hydrolysed by concentrated NaOH(aq) to form product A and product B. Product B has a cleansing property. The structure of Z is shown below : [¢] Il H,C—0—C—C,sH3 [¢] I HC—O0—C—CsHy, [ H,C—0—C—C,sHy, (a) Give the systematic name of product A. () Draw the structure of product B. (©) @) Apart from foam formation, suggest another expected observation when product B is added to an oil-water mixture and shaken. (i) Based on the structure of product B, explain your suggested observation in (c)(i). (1 mark) (1 mark) (1 mark) (2 marks) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-17 17
Answers written in the margins will not be marked. 13. Aluminium, sulphur and chlorine are elements in the third period of the Periodic Table. (@) ®) Based on the products formed (if any) when aluminium oxide reacts with dilute HCl(aq) and with dilute NaOH(aq) respectively, describe the acid-base behaviour of aluminium oxide. (3 marks) Explain, from molecular level, why sulphur is a solid but chlorine is a gas at room conditions. (2 marks) Answers written in the margins will not be marked. Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-18 18
*14. With an addition of NaCI(s) to or an increase in the temperature of the following chemical equilibrium system, there are observable changes in the equilibrium mixtures in these TWO CASES. Co**(aq) + 4CI"(aq) === CoCls**(aq) AH>0 pink blue Considering the effects on the equilibrium position and the equilibrium constant of the system in TWO CASES, state and explain the expected observable changes in these TWO CASES. the above (6 marks) Answers written in the margins will not be marked. END OF SECTION B END OF PAPER Answers written in the margins will not be marked. 2024-DSE-CHEM 1B-19 19 Answers written in the margins will not be marked.