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Soalan pra trial- chem-2012 with answers
 

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    Soalan pra trial- chem-2012 with answers Soalan pra trial- chem-2012 with answers Document Transcript

    • 1Pra- trial chemistry form 5 – MRSM PC – 2012- dated july 2012SECTION A: OBJECTIVE 1. Which of the following shows the correct type of particles for each substance? Atom Molecule Ion A Water Magnesium Sodium Chloride B Magnesium Carbon dioxide Sodium Chloride C Sodium Chloride Carbon dioxide Magnesium D Magnesium Sodium Chloride Carbon dioxide 2. Substance T exists as liquid at temperature of 120 oC. Which of the probable melting point of substance T? Melting point /oC Boiling point /oC A 2 62 B -41 21 C 140 190 D 75 130 3. Which of the following is a use of carbon-14? A. to treat cancer patients B. To estimate the age of fossils and artifacts C. To study the metabolism of phosphorus in plants D. To destroy bacteria in food without changing the quality of the food. 4. Diagram 1 is a graph of temperature – time for heating of substance Q Temperature(oC) 75 t1 t2 Time (s) Diagram 1 Which statement is correct about the property of substance Q based on the graph? A. Is a gas at room temperature B. physical state start changes at temperature 75oC C. Releases heat at time interval t1 and t2 D. Only in liquid condition at time interval t1 and t2 oC
    • 2 5.The following equation represents a reaction What are the reactants in this equation? . Cu(OH)2(s) + 2HNO3(aq) → Cu(NO3)2(aq) + 2H2O(1) A Copper(II) nitrate and water B Copper(II) nitrate and nitric acid C Copper(II) hydroxide and nitric acid D Copper(II) hydroxide and copper(II) nitrate6. Which of the following is not a chemical property of acids? A Reacts with carbonate to produce salt, water and carbon dioxide B Reacts with reactive metal to produce salt and hydrogen C Reacts with metal oxide to produce salt and water D Reacts with alkali to produce salt and hydrogen7. The following equation represents the neutralisation reaction between barium hydroxide, Ba(OH)2 and hydrochloric acid, HCl. Ba(OH)2 + 2HC1 → BaCl2 + 2 H2O What is the volume of 0.5 mol dm hydrochloric acid needed to neutralise 25 cm3 of 0.1 mol dm-3 barium hydroxide? A 2.5 cm3 B 5.0 cm3 3 C 10.0cm D 12.5cm38. Which of the following substances ionise completely in water? I Ammonia II Nitric acid III Ethanoic acid IV Sodium hydroxide A I and II B I and III C II and IV D III and IV9. Some transition elements and their compounds are useful catalysts in industries. Which pair is correct? Catalyst Use in industry A Iron Manufacture of nitric acid from ammonia B Nickel Manufacture of ammonia C Manganese(IV) oxide Manufacture of margarine
    • 3 D Ferum Manufacture of ammonia 10. Which pair is matched correctly? Alloy Major component A Brass Copper B Pewter Zinc C Bronze Tin D Steel Carbon 11. Ammonium sulphate is used as a fertiliser. What is the percentage by mass of nitrogen in ammonium sulphate? [Relative atomic mass: H = 1; N = 14 ; O = 16; S = 32] A 10.6% B 12.3% C 13.3% D 21.2% 12. Which substance is a natural polymer? A Polythene B Polypropene C Polyisoprene D Polyvinyl chloride13. Which factor does not affect the rate of reaction?A. Size of the solid reactantB. Volume of the reactantC. Concentration of the reactantD. Temperature of the reactant14.Which of the following is the correct match of a low rate of reaction and a high rate of reaction? Low rate of reaction High rate of reactionA. Neutralisation between hydrochloric acid and sodium Iron rusting hydroxide solutionB. Double decomposition between lead (II) nitrate solution and Neutralisation between potassium iodide solution hydrochloric acid and sodium hydroxide solutionC. Iron rusting Fermentation of glucose solutionD. Fermentation of glucose solution Double decomposition between lead (II) nitrate solution and potassium iodide solution
    • 415. Which of the following reactants produces the highest rate of reaction with zinc powder?A. 25 cm3 of sulphuric acid 0.1 moldm-3B. 25 cm3 of ethanoic acid acid 0.1 moldm-3C. 25 cm3 of nitric acid 0.1 moldm-3D. 25 cm3 of hydrochloric acid 0.1 moldm-316. An experiment is carried out to determine the rate of reaction between sodium thiosulphate andhydrochloric acid. Which of the following combinations of conditions take the shortest time for the Xmark to disappear from sight? Sulphuric acid Sodium thiosulphate solution Volume/ cm3 Concentration/ Volume/ cm3 Concentration/ Temperature / 0C moldm-3 moldm-3A 10 1.0 50 0.5 30B 10 1.0 50 0.5 40C 10 0.5 50 0.5 30D 20 0.5 40 0.5 4017. Which of the following is not a function of food additives?A Improving the tasteB Adding nutritional valueC Keeping the food tasterD Ensuring nutritional balance18. which substance is used as a food preservative?A Sodium nitriteB Azo compoundC Ascorbic acidD Monosodium glutamate19. which substances is commonly used to manufacture dyes and detergent?A Sulphuric acidB Sodium chlorideC Phosphoric acidD Ammonium chloride20. A patient complained of a pain due to an excess of acid in the stomach. Which of the followingsubstances will help to relieve the pain?
    • 5A AmmoniaB Ethanoic acidC Sodium chlorideD Magnesium hydroxideSECTIONB : STRUCTURE1. Diagram below shows the standard representation for the atoms of two elements, magnesium and chlorine. a. What is represented by the number 24 in ? _________________________________________________________ [1 mark] b. i) Compare the size of the magnesium atom with the chlorine atom. _________________________________________________________ [1 mark] ii) Give a reason for your answer in b. i) above _________________________________________________________ _________________________________________________________ [ 2 mark] c. Complete Table 1 to show the position of chlorine in the Periodic Table. Element Period Group Mg 3 2 Cl [1 mark] d. Magnesium reacts with chlorine to form a compound, magnesium chloride. i) Write the formulae of ions in magnesium chloride. ________________________________________________________ [1 mark] ii) Draw the electron arrangement of the compound formed. [2 marks] iii) State two physical properties of magnesium chloride. _________________________________________________________
    • 6 _________________________________________________________ [2 marks] TOTAL =10M2) Diagram 2 shows the apparatus set-up to study the electrolysis of copper(II) sulphate solution . In Set I, carbon electrodes are used. In Set II, copper electrodes are used. Copper(II) sulphate solution carbon copper Set I Set II Diagram 2 (a) State all the anions and cations in copper(Il) sulphate solution. Anion: …………………………………………………………………………… Cations: ………………………………………………………………………….. [2m] (b) Based on Set 1 in Diagram 2: (i) Write the formula of the ion that is selectively discharged at the cathode. ………………………………………………………………………… [l m] (ii) State reason for your answer in (b) (i) above ……………………………………………………………………. [ 1m] (iii) Write the half-equation for the reaction that takes place at the cathode. ……………………………………………………………………[2 m] (iii) State the observation at the cathode.
    • 7 ………………………………………………………………………… [1 m] (c) Based on Set 2 in Diagram 2: (i) Name the product formed at anode …………………………………………………………………………... [1m] (d) Compare the intensity of blue colour of the copper(Il) sulphate solutions in Set I and Set II after one hour of electrolysis. Give one reason for the answer. Comparison: ............................................................................................................................... ............................................................................................................................... Reason: ………………………………………………………………………………… ………………………………………………………………………………… [2 m] Total =10m 3 . Diagram 3 below shows laboratory activities in preparation of a salt. Excess zinc oxide powder50 cm3 2 .0 mol/dm3 nitric acid heat heat Diagram 3 (a) Is the preparation of salt above for soluble salt or insoluble salt? …………………..……………………………………………………………… [1 mark] (b) Explain why zinc oxide powder is added in excess.
    • 8………………..………………………………………………………………………… [1 mark](c) Write a chemical equation for the reaction that occurs inside the beaker.…………………..……………………………………………………………………… [1 mark](d) Draw the apparatus set-up used to separate the excess zinc oxide powder from the mixture inthe box in diagram 3 above. [2 marks](e) name the salt formed…………………………………………………………………………………………….[1 mark](f)Calculate the maximum mass of the salt formed. in ( e )[Relative atomic mass: N=14, O=16, Zn=65][3 marks](g) Suggest one substances that can replace zinc oxide in the experiment to obtain the same typeof salt.………………….………………………………………………………………………………………… [1 marks] Total = 10 m4. Table below shows the heat of neutralisation of two different monoprotic acids, P and Q with sodium hydroxide solution.
    • 9Experiment Reactants Heat of neutralisation/ kJmol-1 I 100cm3 1.0 moldm-3 sodium hydroxide solution + -55.0 100cm3 1.0 moldm-3 of monoprotic acid P II 100cm3 1.0 moldm-3 sodium hydroxide solution + -57.0 100cm3 1.0 moldm-3 of monoprotic acid Qa) What is the meaning of heat of neutralisation? ___________________________________________________________________________ ___________________________________________________________________________ [1 mark]b) State one example which could be acid P and acid Q P - ____________________________________________________ Q - ____________________________________________________ [2 marks]c) Calculate the change in temperature of the mixture in experiment I [Specific heat capacity of solution: 4.2 Jg-1C-1] [3 marks]
    • 10 d) i) Compare the value of heat neutralisation in experiment I and II _________________________________________________________________________ [1 mark] ii) Briefly explain your answer in d(i) _________________________________________________________________________ _________________________________________________________________________ [2 marks] e) Draw the energy level diagram for reaction in experiment II [2 marks] Total marks = 11 Max mark=10m(5) Table 5 shows the molecular formulae and boiling points for three compounds, which are members of a homologous series. Compound Molecular formula Boiling point ( 0C) P C2H4 -103 Q C3H6 -48 R C4H8 -6 Table 5 (a) (i) Name the homologous series for these compounds.
    • 11 ……………………………………………………………………………………………………………………………………….. [ 1 mark] (ii) Write the general formula for this homologous series. …………………………………………………………………………………………………………………………………….. [ 1 mark] (b) Explain why the boiling point for the members of this homologous series increase when the number of carbon atoms per molecule increases. …………………………………………………………………………………………………………………………………………………… …………………………………………………………………………………………………………………………………………………… ………………………………………………………………………………………………………………………………………………….. [ 3 marks]( c) Write the chemical equation when compound P reacts with steam in the presence of phosphoric acid at temperature of 300 0C at 60 atm pressure. ……………………………………………………………………………………………………………………………………… …………… [2 marks] ( d) Compound P undergoes polymerisation. The structural formula for compound P is given below. Write the equation for the polymerisation of compound P. …………………………………………………………………………………………………………………………………… [ 2 marks](e) Draw the structural formula for Q. [ 1 mark]
    • 12 Total= 10m6. Diagram 6 shows the apparatus set-up for an experiment to investigate electron transfer at a distance in redox reactions. Carbon X Potassium iodide solution Acidified potassium dichromate(VI) solution Sodium sulphate solution Diagram 6 (a) State the colour of acidified potassium dichromate(VI) solution . ………………………………………………………………………………..[l m] (b) When the circuit is completed, the galvanometer shows a deflection. (i) Write the half-equation for the reaction at X. ………………………………………………………………………[l m] (ii) State the type of reaction in 6(b)(i). ………………………………………………………………….……[l m] (iii) Describe briefly a chemical test to identify the product formed in 6(b)(i). ……………………………………………………………………………… ……………………………………………………………………………… ……………………………………………………………………………… [2marks] (c) (i) The half-equation below shows the reaction that occurs in acidified potassium dichromate(Vl) solution. Complete the half-equation. Cr2O72- + …….. H+ + …….. e → ….. Cr3+ + ……. H2O [2m] (ii) Based on the answers in 6(b)(i) and 6(c)(i), on Diagram 6, draw the arrows to show the direction of electron flow. [1m] (d ) State the function of sodium sulphate solution
    • 13 ……………………………………………………………………………………………… [1m] (e) name the substance that can replace potassium iodide solution as the redox reaction occurs ……………………………………………………………………………………………… [1m] Total mark=10mPaper 3 7. A student carried out an experiment to investigate the rate of reaction between 5 g of large marble chips and crushed marble chips with 50 cm3 hydrochloric acid 1.0 mol dm-3 . Table 7 shows the data obtained from the experiment. Time Set 1 Set 2 (s) Hydrochloric acid and 5.0 g large Hydrochloric acid and 5.0 g marble chips crushed marble chips Burette Volume of gas Burette Volume of gas reading (cm3) evolved (cm3) reading evolved (cm3) (cm3) 0 50.00 0.00 50.00 0.00 30 38.00 12.00 36.00 14.00 60 30.50 19.50 29.50 20.50 90 120 22.00 28.00 19.00 31.00 150 19.50 30.50 18.00 32.00 180 18.50 31.50 18.00 32.00
    • 14210 18.00 32.00 18.00 32.00240 18.00 32.00 18.00 32.00 Table 7Diagram 7 shows the burette reading at 90 seconds for set 1 and set 2. Diagram 7a) Based on Diagram 7, record the burette readings and volume of gas evolved at 90 seconds for both set in Table 7. [3 marks]b) Based on Table 7, state how the volume of gas evolved changes when the marble chips react with hydrochloric acid in Set 1. ______________________________________________________________ ______________________________________________________________ [3 marks]c) Based on this experiment, state the: i. Manipulated variable :___________________________________ ii. Responding variable :___________________________________ iii. Constant variable :___________________________________ [3 marks]d) State the operational definition for the rate of reaction. ______________________________________________________________ ______________________________________________________________ [3 marks]
    • 15SECTION C; ESSAY 8(a) Diagram 8 shows the apparatus and observations for a redox reaction between iron(III) chloride solution and a metal. At the beginning of the experiment After 30 minutes Diagram 8
    • 16 Based on the observations shown in Diagram 9, suggest a suitable metal to be used in this experiment. Predict the ion present in the green solution and explain the answer based on the following aspects: • The change in oxidation number for both the reactants • The type of reaction that has occurred to each reactant • The role of each reactant in the redox reaction • The half-equations involved in the redox reaction [10 marks] ……………………………….END OF QUESTION PAPER………………………………Answer scheme pra-trial 2012Objective answer 1 B 2 D 3 B 4 B 5 C 6 D 7 C 8 C
    • 17 9 D 10 A 11 D 12 C 13 B 14 D 15 A 16 B 17 D 18 A 19 A 20 DSTRUCTURED QUESTIONS No Mark scheme Mark 1a Nucleon number// atomic mass// total number of protons and 1 neutrons b) i Chlorine atom is smaller than magnesium atom/(vice versa) 1 ii) Proton number of chlorine is more than in magnesium 1 Nuclei attraction in chlorine atom is more than in magnesium 1 atom c Period: 3 Group: 17 1 d i Mg2+, Cl- 1 ii 1. Correct no of electrons in each shell 1 2. Correct charges and label nucleus 1 iii • High melting point/ boiling point • Soluble in water/ insoluble in organic solvent • White solid • Conduct electricity in molten or aqueous solution (any two) 2 10
    • 18Answers Mark2. (a) Anion : SO42- and OH- 1 Cation :Cu2+ and H+ 1 (b) (i) Cu2+ 1 (ii) The position of Cu2+ ion is lower than H+ ion in Electrochemical 1 Series (iii) Half equation at cathode Cu2+ + 2e Cu 2 (iv) Brown solid is deposited 1 (c) Copper (ll) ion 1 (d) Comparison : The intensity of blue colour in Set 1 will decrease/fade 1 but in set 2 the intensity of blue colour remain unchanged Reasons : The concentration of Copper(ll) ions dereases in set 1 but 1 remain unchanged in set 2 Max : 10m Suggested Answer mark3.a Soluble salt 1m b To ensure all the acid react completely 1m c ZnO + 2HNO3 Zn(NO3)2 + H2O 2m d Excess zinc oxide 2m [functional apparatus] 1 m [label] 1 m e Zinc nitrate 1mf (e) Number mole of nitric acid = 2(50)/1000 = 0.1 mol 1m 2 mol HNO3  1 mol Zn(NO3)2 0.1 mol HNO3  0.1/2 x 1 mol Zn(N03)2  0.05 mol Zn(NO3)2 1m Mass of salt = 0.05 x (65 + 2(14) + 6(16) =0.05x189 = 9.45 g 1mg Zinc carbonate / zinc 1m total 11m Max=10m
    • 19No. Answers Marks4.a) Heat change when 1 mol of water is formed from 1 mol H+ ion and 1 1 mol OH- ionb) Q - nitric acid / hydrochloric acid 1 P – ethanoic acid 1c) nNaOH = 100 (1.0) = 0.1 1 1000 ∆H = H ; H = ∆H x n n = 55000 x 0.1 = 5500 J 1 H = mcᴓ ᴓ = 5500 200(4.2) = 6.5 0C 1d) i) Heat of neutralisation in experiment II is higher than heat of 1 neutralisation in experiment Id) ii) - Some heat given out during neutralisation 1 - Is used to dissociate the acid molecules completely 1e) H+ + OH- ∆H= - 57 kJmol-1 - 1 - 1 H20
    • 20 Suggested Answer mark5.a.i Alkenes 1ma.ii CnH2n n=2,3...... 1m b When the number of carbon atom increase the molecular weight also 1m increase So the attraction force between molecule increase 1m Hence more energy is needed to overcome that force 1m c C2H4 + H2O  C2H5OH 2md 2m n e 1m total 10m6. Diagram 6 shows the apparatus set-up for an experiment to investigate electron transfer at a distance in redox reactions. (a) State the colour of acidified potassium dichromate(VI) solution . ……Orange ……………………………………………………..[l m] (b) When the circuit is completed, the galvanometer shows a deflection. (i) Write the half-equation for the reaction at X. 2I-  I2 + 2e ……[l m] (ii) State the type of reaction in 6(b)(i). ………oxidation …………………………….……[l m] (iii) Describe briefly a chemical test to identify the product formed in 6(b)(i).
    • 21 ………Add starch solution to the product formed Dark blue solution is formed OR Add 1,1,1 trichloroethane solution Purple colour at the lower layer formed……. [2 m] (c) (i) The half-equation below shows the reaction that occurs in acidified potassium dichromate(Vl) solution. Complete the half-equation. Cr2O72- + …14. H+ + …6.. e → 2 Cr3+ + …7. H2O [2m] (ii) Based on the answers in 6(b)(i) and 6(c)(i), on Diagram 6, draw the arrows to show the direction of electron flow. [1m]d. to allow the movement of ion to complete the circuit ………………………….1me. Ferum (II) sulphate …………………………………………………..1mMARKING SCHEME FOR ESSAY Answer Marks 8 Suggested metal : Zinc and magnesium 1 The ions present in the green solution are Fe2+ and ( H+ and OH- from 1 water ) • The change in oxidation number of Fe is from +3 to +2 1 • Fe3+ undergoes reduction reaction 1 • The change in oxidation number of Mg is from 0 to +2 1 • Mg undergoes oxidation reaction 1 • Fe3+ acts as oxidizing agents because oxidizes Mg to Mg2+ 1 • Mg as reducing agents because reduces Fe3+ to Fe2+ 1
    • 22 • Half equation (oxidation) Mg Mg2+ + 2e 1 • Half-equation (Reduction) Fe3+ + e Fe2+ 1 Max Mark : 10PAPER 3 ANSWER SCHEME Question Mark Scheme Marks 7 (a) Able to record the burette readings accurately and write the volume of gas 3 correctly Answer: Set 1 25.50 24.50 Set 2 20.00 30.00 Able to record the burette readings accurately and write the volume of gas 2 correctly Answer: 90 25.50 24.50 120 20.0 30.0 Or
    • 23 90 25.5 24.5 120 20.0 30.0 Or 90 25.5 24.5 120 20. 30. Able to record at least one burette reading less accurately 1 Sample answer: 25.5// 22 No response or wrong response 0Question Mark Scheme Marks7 (b) Able to state the change of volume of gas evolved accurately 3 Sample answer: The volume of gas increases until (210 seconds/ 32.0 cm3/ remain/ maximum/ constant/ final volume) Able to state the change of volume of gas evolved less accurately 2 Sample answer: The volume of gas increases. Able to give an idea on the change of volume of gas evolved 1 Sample answer: The volume of gas change. r: remain only No response or wrong response 0Question Mark Scheme Marks
    • 247 (c) Able to state all the variables correctly 3 Sample answer: Manipulated variable: size of marble chips/ total surface area of marble chips Responding variable: rate of reaction/ volume of gas per unit time Constant variable: hydrochloric acid, marble chips, mass of marble chips, temperature of acid, volume and concentration of hydrochloric acid (any correct two) Able to state all the variables less correctly 2 Sample answer: Manipulated variable: marble chips Responding variable: volume of gas constant variable: hydrochloric acid, marble chips, mass of marble chips, temperature of acid, volume and concentration of hydrochloric acid (any correct two) Able to give idea for all the variables 1 Sample answer: Manipulated variable: marble chips Responding variable: volume of gas Constant variable: hydrochloric acid No response or wrong response 0Question Mark Scheme Marks7(d) Able to state the operational definition rate of reaction correctly 3 Sample answer: Volume of gas over/per time/second// rate = volume of gas evolved/time taken a: volume of gas in one second. * [Formula form] Note: Volume of gas in minute  score 2 Volume of gas in 30 seconds  score 2 Volume of gas in every 30s  score 1 Volume of gas at 30s  score 1 Able to state the operational definition rate of reaction less correctly 2 Sample answer: Volume of gas per minutes/ hours // 32/210// time taken for certain volume of gas collected// volume of gas evolved in fixed time. a: change/ increase of volume of gas against time. a: change of reactants/ products over time (more than idea) Able to give an idea of operational definition of the rate of reaction 1 Sample answer: The change/ increase/ decrease in the amount of [products]/[reactants]// [time taken] a: rate of [products]/ [reactants] produce.
    • 25a: any products / reactants.No response or wrong response 0