LW F6 Chem Mock Exam P1 1718

F.6 Chemistry Paper I P.1 / 23 SKH LAM WOO MEMORIAL SECONDARY SCHOOL Mock Examination (2017-2018) F.6 Chemistry Paper 1 Date: 30/01/2018 (Tuesday) Time allowed: 2 hours 30 minutes Section A: Multiple-choice Questions (36 marks) 1. Three metals P , Q and R are added to copper(II) sulphate solution separately. The results are shown below: Metal Reaction with copper(II) sulphate solution P Brown solid formed and colourless gas bubbles evolved Q No observable change R Brown solid formed Which of the following is the correct order of the reactivity of the three metals? A. P < Q < R B. R < Q < P C. Q < R < P D. P < R < Q 2. Which of the following statements about NF 3 and NH 3 are INCORRECT? (1) Both NF 3 and NH 3 molecules are planar. (2) Both NF 3 and NH 3 molecules are non-polar. (3) The boiling point of NH 3 is lower than that of NF 3 . (4) Hydrogen bond exists in both NH 3 and NF 3 . A. (1) and (2) only B. (3) and (4) only C. (2), (3) and (4) only D. (1), (2), (3) and (4) 3. Which of the following substances CANNOT be used to distinguish between concentrated hydrochloric acid and concentrated nitric acid? A. Copper turnings B. Potassium iodide solution C. Silver nitrate solution D. Marble chips 4. The following diagram shows how the components of air can be separated in a fractionating column:

F.6 Chemistry Paper I P.2 / 23 Which of the following statements concerning the gases being separated out is INCORRECT? A. The ascending order of the boiling points of gases A , B and C is A < B < C . B. The percentage by volume of gas A in air is 78%. C. Gas B exists as diatomic molecules in the atmosphere. D. The solution produced by dissolving gas D in water is an essential component of soft drinks. 5. 3.1 g of element Z reacts completely with 2.4 g of O 2 gas to form an oxide. The molar mass of the oxide is 220 g mol − 1 . Which of the following could be the molecular formula of the oxide? A. Z 2 O 3 B. Z 4 O 6 C. Z 6 O 9 D. Z 8 O 12 6. 200 cm 3 of 2 M sodium hydroxide solution is mixed with 300 cm 3 of distilled water. Then, 6.0 g of sodium hydroxide pellets is added to the solution and dissolves completely. What is the molarity of the resultant sodium hydroxide solution? A. 0.73 M B. 1.10 M C. 1.83 M D. 2.75 M 7. The energy density of a substance is the energy given out when one gram of it is completely burnt. Consider the information below: Substance Standard enthalpy change of combustion / kJ mol − 1 CH 4 (g) − 890.4 C 2 H 5 OH(l) − 1371 C 8 H 18 (l) − 5460 Gasoline with 10% C 2 H 5 OH(l) and 90% C 8 H 18 (l) − y Which of the following substances has the highest value of energy density (kJ g − 1 )? A. CH 4 (g) B. C 2 H 5 OH(l) C. C 8 H 18 (l) D. Gasoline gas A gas B gas C air gas D and water vapour are removed

F.6 Chemistry Paper I P.4 / 23 D. The same observation can be made if dilute sulphuric acid is replaced by concentrated sulphuric acid. 11. 1.23 g of propan-1ol is burnt completely to heat up a certain mass of water inside a calorimeter. The temperature rise of the calorimeter is 5.8  C. 2.01 g of ethanol is burnt completely in another calorimeter of the same material but with a double mass of water inside. The temperature rise of the calorimeter is 4.1  C. What is the standard enthalpy change of combustion of propan-1-ol if the standard enthalpy change of ethanol is ‒ 1371 kJ mol ‒ 1 ? (specific heat capacity water = 4.2 J g − 1 K − 1 ) A. − 1019 kJ mol − 1 B. − 2010 kJ mol − 1 C. − 2067 kJ mol − 1 D. − 4074 kJ mol − 1 12. In order to prepare 200 cm 3 of 0.3 M oxalic acid, what is the mass of oxalic acid crystals (H 2 C 2 O 4 • 2H 2 O) required? A. 7.56 g B. 6.57 g C. 4.59 g D. 3.35 g 13. Which of the following changes would NOT occurred in a zinc-carbon cell? A. Zinc is oxidized to form zinc ions. B. Ammonium ion is reduced to form hydrogen. C. Hydrogen is oxidized to form hydrogen ions. D. Manganese(IV) oxide is reduced to form manganese(III) oxide. 14. A white pure solid gives a brick-red flame in a flame test. When passing Cl 2 into the aqueous solution of the solid, the solution turns brown. After that, heptane is added to the resultant solution. The heptane layer turns purple. Which of the following is probably the white solid? A. Calcium bromide B. Calcium iodide C. Sodium bromide D. Sodium iodide 15. The structures of hydrocarbons X and Y are shown below: X Y Both X and Y react with bromine (in organic solvent). Which of the following statements about the two reactions is correct? A. The two reactions can occur in the dark. B. The reaction between X and bromine forms di-brominated products only. C. The reaction between Y and bromine forms mono-brominated products only. D. The two reactions are redox reactions.

F.6 Chemistry Paper I P.5 / 23 16. Polybut-1-ene is manufactured from petroleum by the following route: Which of the following statements is correct? A. The relative molecular mass of polybut-1-ene is a constant. B. Processes 1 & 2 involve physical changes while process 3 involves chemical change. C. But-1-ene and polybut-1-ene have different empirical formulae. D. Polybut-1-ene is resistant to concentrated hydrochloric acid. 17. The following experiments have been done to study the reactivity of element X : (1) X can displace lead from lead(II) nitrate solution. (2) Heated X can react with steam. (3) X shows no observable change when added to cold water. Which of the above experiments show that X is more reactive than copper? A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) 18. Which of the following statements about diamond, graphite and C 60 are INCORRECT? (1) Diamond, graphite and C 60 form different products when they undergo complete combustion. (2) For 6 g of diamond, there are 0.5 × 6.02 × 10 23 C − C bonds. (3) Diamond and C 60 have high melting points owing to their giant covalent structures. (4) Diamond, graphite and C 60 are allotropes. A. (1) and (2) only B. (3) and (4) only C. (2) and (4) only D. (1), (2) and (3) only 19. Consider the following electrolytic cells: (1) (2) Petroleum But-1-ene Fuel oil Polybut-1-ene Process 1 Process 2 Process 3 graphite electrode silver electrode silver nitrate solution silver electrode silver electrode silver nitrate solution

F.6 Chemistry Paper I P.7 / 23 A (l) + 9O 2 (g) → 7CO 2 (g) + 4H 2 O(l) Δ H 1 = − x kJ mol − 1 B (l) + 9O 2 (g) → 7CO 2 (g) + 4H 2 O(l) Δ H 2 = − y kJ mol − 1 Which of the following statements are correct? (1) The value of y is greater than x . (2) The energy content of B is higher than that of A . (3) The conversion of B to A is an exothermic reaction. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) Directions: Each question below (Questions 23 to 24) consists of two separate statements. Decide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from A to D according to the following table: A. Both statements are true and the 2nd statement is a correct explanation of the 1st statement. B. Both statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. C. The 1st statement is false but the 2nd statement is true. D. Both statements are false. 1st statement 2nd statement 23. When equal masses of strontium and calcium react with excess hydrochloric acid, calcium gives more hydrogen than strontium does when the reaction is completed. Strontium has a larger relative atomic mass than calcium. 24. We can obtain hydrogen gas from the reaction of dilute nitric acid with copper. Dilute nitric acid is a strong acid. 25. Consider the following set-ups. Beakers X and Y contain sodium thiosulphate and hydrochloric acid of different volumes and concentrations. The total volume of solutions in beaker Y is larger than that in beaker X . S 2 O 3 2 − (aq) + 2H + (aq) → SO 2 (g) + H 2 O(l) + S(s) The times needed for the cross on the paper to blot out are the same for both beakers X and Y . Which of the following statements about this experiment is correct? white paper marked with a cross beaker X Na 2 S 2 O 3 (aq) + HCl(aq) beaker Y

F.6 Chemistry Paper I P.8 / 23 A. Hydrogen ion is the reducing agent. B. The progress of reaction can also be followed by measuring the volume of sulphur dioxide produced. C. The rates of formation of sulphur in the two beakers are the same. D. Hydrogen ion is used as a catalyst. 26. Which of the following methods is NOT useful in distinguishing between magnesium oxide and silicon dioxide? A. Adding dilute sulphuric acid B. Adding warm concentrated sodium hydroxide solution C. Measuring their electrical conductivity under room conditions D. Adding water and then measuring the pH values of the resultant solution 27. Consider the following equilibrium system in a closed vessel of fixed volume: 2NO 2 (g) N 2 O 4 (g) Δ H < 0 Given that NO 2 is a brown gas while N 2 O 4 is a colourless gas. Which of the following would occur if the temperature of the equilibrium system is lowered? (1) The colour intensity of the reaction mixture decreases. (2) The pressure of the system decreases. (3) The density of gaseous mixture decreases. A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) 28. Nitroglycerin (C 3 H 5 N 3 O 9 ) can be used as an explosive. When it is ignited, it decomposes to carbon dioxide, nitrogen, oxygen and water vapour. 4C 3 H 5 N 3 O 9 (s) → 12CO 2 (g) + 6N 2 (g) + O 2 (g) + 10H 2 O(g) What is the theoretical volume of gas (measured at room temperature and pressure) that can be collected when 22.7 g of nitroglycerin is ignited? (molar volume of gas at room temperature and pressure = 24.0 dm 3 mol − 1 ) A. 11 400 cm 3 B. 17 400 cm 3 C. 22 200 cm 3 D. 69 600 cm 3 29. The equilibrium constant of the following reaction at a certain temperature is 14.8 mol − 2 dm 6 . N 2 (g) + 3H 2 (g) 2NH 3 (g) At this temperature, 10.0 moles of nitrogen is present in a 10.0 dm 3 container. How many moles of hydrogen are needed initially in order to convert half of the nitrogen into ammonia at equilibrium? A. 1.50 mol B. 5.13 mol C. 6.63 mol D. 20.1 mol

F.6 Chemistry Paper I P.10 / 23 C. polymerization. D. dehydration. 34. Consider the following reversible reaction: 2H 2 O(g) + 2Cl 2 (g) 4HCl(g) + O 2 (g) Equal volumes of water vapour and chlorine are placed in a closed vessel and an equilibrium is reached. Which of the following relationships is/are correct? (1) [Cl 2 (g)] < [O 2 (g)] (2) [H 2 O(g)] = [Cl 2 (g)] (3) 4[HCl(g)] = [O 2 (g)] A. (1) only B. (2) only C. (1) and (3) only D. (2) and (3) only 35. Which of the following compounds can be used for synthesizing propanamide? (1) CH 3 CH 2 COOCH 3 (2) CH 3 CH 2 COOH (3) CH 3 CH 2 CHO A. (1) and (2) only B. (1) and (3) only C. (2) and (3) only D. (1), (2) and (3) Directions: Each question below (Question 36) consists of two separate statements. Decide whether each of the two statements is true or false; if both are true, then decide whether or not the second statement is a correct explanation of the first statement. Then select one option from A to D according to the following table: A. Both statements are true and the 2nd statement is a correct explanation of the 1st statement. B. Both statements are true but the 2nd statement is NOT a correct explanation of the 1st statement. C. The 1st statement is false but the 2nd statement is true. D. Both statements are false. 1st statement 2nd statement 36. The initial rate of the reaction between iodide ions and peroxodisulphate ions (S 2 O 8 2 − ) is low. The reaction between iodide ions and peroxodisulphate ions involves the collisions of negatively charged ions. END OF SECTION A

F.6 Chemistry Paper I P.11 / 23 Section B: Conventional Questions (84 marks) 1. Titanium is a useful metal and is the ninth most abundant element i n the Earth’s crust. (a) Titanium (relative atomic mass = 47.9) has five isotopes in nature: 46 Ti, 47 Ti, 48 Ti, 49 Ti and 50 Ti. The relative abundance of each isotope is shown below: Isotope Relative abundance (%) 46 Ti 8.3 47 Ti x 48 Ti 73.7 49 Ti y 50 Ti 5.2 (i) Determine the values of x and y . (ii) 47 Ti can react with hydrofluoric acid (HF(aq)) to form complex anions [ 47 TiF 6 ] 3 − (aq), hydrogen gas and hydrogen ions. The mole ratio of hydrogen gas and hydrogen ions is found to be 1:2. Write the chemical equation, with state symbols, for the reaction involved. (iii) Is the reaction in (ii) a redox reaction? Explain your answer. (iv) 48 Ti is used instead of 47 Ti to react with hydrofluoric acid. When a burning splint is put at the mouth of the reaction flask , will it burn with a ‘pop’ sound? Explain briefly. (5 marks)

F.6 Chemistry Paper I P.13 / 23 (ii) The student is given the same tricarballylic acid sample and a pH meter. Describe briefly how to determine whether tricarballylic acid is a strong or weak acid. Explain your answer. 2. (b) (iii) It is known that tricarballylic acid is a weak acid. Phosphoric acid (H 3 PO 4 ) is another strong tribasic acid. There are 25.0 cm 3 of phosphoric acid of the same concentration as the tricarballylic acid sample in (i). Would the volume of 0.35 M sodium hydroxide solution required for complete neutralization, compared to that required in (i), be larger, smaller or the same? Explain your answer. (6 marks) (c) Trimesic acid is another tribasic acid. Its chemical structure is shown below:

F.6 Chemistry Paper I P.14 / 23 The student suggests using acidified potassium permanganate solution to distinguish between tricarballylic acid and trimesic acid. Comment on the suggestion. (1 mark) 3. Zinc is a useful metal. It is commonly used in zinc-plating and making alloy. (a) Explain, in terms of structure, why zinc can conduct electricity. (2 marks) (b) (i) Explain why zinc-plating can prevent iron from rusting. (ii) When the zinc coating is damaged, can zinc still protect iron from rusting? Explain your answer. (3 marks) (c) An alloy consists of zinc, aluminium and copper. An alloy sample is analysed. (i) Dilute sulphuric acid is added to the alloy sample. State TWO observable changes. (ii) An analysis shows that the sample contains 5.494 g of zinc, 0.566 g of aluminium and 8.001 g of copper. Calculate the empirical formula of this alloy. (4 marks)

F.6 Chemistry Paper I P.16 / 23 Method 1: remove the stains using sodium sulphite solution Method 2: remove the stains using 1,1,1-trichloroethane State the principle behind each method. Determine which method is better and explain briefly. (4 marks) 6. Alkanes and alkenes undergo some organic reactions. (a) Large alkane molecules undergo cracking to form smaller hydrocarbon molecules. When 1 mole of docosane (C 22 H 46 ) is cracked, 2 moles of alkene A and 1 mole of C 14 H 30 form. (i) What is the chemical formula of A ? (ii) C 14 H 30 obtained is mixed with bromine and chlorine under diffuse sunlight respectively. Which reaction, the reaction with bromine or chlorine, will be more vigorous? Explain your answer. (iii) What would be observed when the product mixture of cracking is mixed with acidified potassium permanganate solution and acidified potassium dichromate solution respectively? Give the chemical equation(s) if there are any reaction(s) taking place. (5 marks)

F.6 Chemistry Paper I P.17 / 23 6. (b) Alkenes are important organic compounds as they undergo addition polymerization to form various useful products. Polyvinyl chloride (PVC) and polyvinylpyrrolidone (PVP) are two examples of addition polymers. (i) Suggest one use of polyvinyl chloride. (ii) PVC undergoes combustion in incinerators to give hydrogen chloride, carbon dioxide and water vapour. Write the equation for the reaction involved. You may use the repeating unit to represent the chemical formula of PVC. (iii) The structure of the monomer of PVP is shown below: Draw the structure of PVP. (3 marks) 7. In biological fuel cells, a current is produced by the biological operations of bacteria. They work well between 20  C and 40  C and at a pH value around 7. Biological fuel cells can be applied in wastewater treatment. Wastewater with bacteria is introduced into one of the compartments of the fuel cell. Bacteria convert sucrose (C 12 H 22 O 11 ) and water into carbon dioxide gas and hydrogen ions. In another compartment, air is introduced. The air component that has a percentage by volume of 21% is converted into water.

F.6 Chemistry Paper I P.19 / 23 (2 marks) (d) Scientists are investigating the possibility of using such biological fuel cell as an energy source for medical applications such as pacemakers. Comment whether it is feasible or not. (1 mark) 8. The dissociation of water is an endothermic and reversible reaction. The equation is shown below: H 2 O(l) H + (aq) + OH − (aq) (a) Write an expression for the equilibrium constant (K c ) for the above dissociation. (1 mark) (b) Given that K c = 2.50 × 10 − 14 mol 2 dm − 6 at body temperature (i.e. 37  C). What is the pH value of water at body temperature? (2 marks) (c) A student did an experiment to investigate the effect of dissociation of water on human bodies. He carried out all the experimental procedures at 37  C. However, he wrongly used the K c of the dissociation of water at 25  C in calculation. How does this affect the calculated pH value of water? Explain briefly. (2 marks)

F.6 Chemistry Paper I P.20 / 23 (d) Ammonium sulphate ((NH 4 ) 2 SO 4 ) is added to distilled water. After some times, the pH of the solution is measured. It is found that the pH value has dropped. Explain the phenomenon with the aid of an ionic equation. (3 marks) 9. In the Contact process, vanadium(V) oxide is used as the catalyst. The reaction involves the following two steps. Step 1: SO 2 (g) + V 2 O 5 (s) → SO 3 (g) + 2 X (s) Step 2: 2 X (s) + 2 1 O 2 (g) → V 2 O 5 (s) (a) Give the chemical formula of X . (1 mark) (b) Briefly describe the role of oxygen in the above processes. (2 marks) (c) With reference to the above catalysis as an example, explain why transition metals and their compounds show catalytic properties. (1 mark)