Chemistry Monday 4 November 2013 Paper One Question and response book

Transcription

1 2013 Senior External Examination Chemistry Monday 4 November 2013 Paper One Question and response book 9 am to 11:40 am Time allowed Perusal time: 10 minutes Working time: 2 hours 30 minutes Examination materials provided Paper One Question and response book Paper One Part A Multiple-choice response sheet Paper One Resource book Equipment allowed QSA-approved equipment non-programmable calculator Directions Do not write in this book during perusal time. Paper One has two parts: Part A Knowledge of subject matter: Section 1 Multiple choice (attempt all questions) Section 2 Short response (attempt all questions) Part B Scientific processes (attempt four questions only) Candidate use Print your candidate number here 1 3 Attach barcode here Number of books used Supervisor use only Supervisor s initials QSA use only Marker number Suggested time allocation Part A: 1 hour 50 minutes Part B: 40 minutes Assessment Paper One assesses the following assessment criteria: Knowledge of subject matter Scientific processes Assessment standards are at the end of this book. After the examination session The supervisor will collect this book when you leave.

2 Planning space

3 Part A Knowledge of subject matter Part A assesses knowledge of subject matter and its simple application based on the topics in the Chemistry Senior External Syllabus 1998 (amended 2006). Part A is worth 80 marks. Suggested time allocation: 1 hour 50 minutes. Section 1 Multiple choice Section 1 has 10 questions of equal value. Attempt all questions. Each question contains four options. Select the option that you think is correct or is the best option. Respond on the multiple-choice response sheet. Question 1 Which of the following pairs represent isotopes of the fictitious element Z? A B C D 84 Z 36 and 30Z 54 Z 26 and 26Z 10 Z 5 and 10Z 1 Z and Z Question 2 Ammonium acetate has the formula CH 3 CO 2 NH 4. From this it can be concluded that A B C D there are twelve atoms per formula unit. there are six different elements in the compound. carbon makes up 2 / 12 of the mass of the compound. the compound is very reactive because of the presence of the seven H atoms. Question 3 A compound which melts at 815 C and does not conduct electricity as a solid but does so when dissolved in water could be composed of A B C D ions in a three dimensional lattice. atoms held together by covalent bonds. molecules in a three dimensional lattice. molecules held together by hydrogen bonds Chemistry Paper One Question and response book 1

4 Question g of hydrogen gas is reacted with 10.0 g of oxygen gas in a closed container. When the reaction is complete, the mass of substances in the container is A 1.0 g. B 8.0 g. C 9.0 g. D 11.0 g. Question 5 Fluorine reacts spontaneously with bromide ions according to the following equation: F 2 g + 2Br aq 2F aq + Br 2 g Which of the following is the strongest oxidising agent? A B C D F 2 (g) Br (aq) F (aq) Br 2 (g) Question 6 Which of the following molecules is a structural isomer of propanoic acid? A B C D H H H O H C C C C OH H H H H H O HO C C C OH H H H H H O C C C O H HO H C C C OH H H H Chemistry Paper One Question and response book

5 Question 7 A section of the periodic table has had the chemical symbols replaced by letters. K L M N The element which belongs to the d block of the periodic table is A K. B L. C M. D N. Question 8 A sample of gas is held in a closed container at a temperature of 10 C. What final temperature would be required in order for the average kinetic energy of the particles to be doubled? A 20 C B 120 C C 283 C D 293 C Question 9 An accurate description of a 6M solution of CH 3 COOH (acetic acid) of Ka = 1.8 x 10 5 would be a A B C D dilute weakly acidic solution. dilute strongly acidic solution. concentrated weakly acidic solution. concentrated strongly acidic solution Chemistry Paper One Question and response book 3

6 Question 10 During the progress of a chemical reaction, A B C D most collisions involve only two particles. a successful collision is one in which the reactants are formed again. the activated complex has a lower energy than either reactants or products. the rate can be determined by an inspection of the relevant chemical equation. End of Section Chemistry Paper One Question and response book

7 Section 2 Short response Section 2 has eight questions. Attempt all questions. Write your responses in the spaces provided. Show all working. If you need more space for a response, continue on page 26 of this book. Label any continued response with the question number. Question 11 Materials: Properties, bonding and structure a. An atom of an element contains 18 neutrons and 17 electrons. i. What is the atomic number? ii. (½ mark) What is the mass number? (½ mark) b. List the type of attractive force that is overcome when each of the following substances melt. Substance Force Copper Copper sulfate Ice Diamond (2 marks) c. Give the formula for the sulfate ion.... d. Name the substance represented by the formula Mg(OH) 2. (½ mark) Chemistry Paper One Question and response book 5

8 e. For each pair listed below, state an experimental test that could be used to distinguish between the two. How would the results differ for each test? Pure water/solution of sodium chloride in water Test: Results: Iron sulfide/mixture of iron and sulfur Test: Results: f. Draw Lewis diagrams for the following molecules and give the shape of each molecule.. Molecule Lewis diagram Shape of molecule (3 marks) CH 4 NCl 3 (2 marks) Chemistry Paper One Question and response book

9 Question 12 Reacting quantities and chemical analysis a. Define the following terms: i. Avogadro s number ii. relative atomic mass b. Balance the following equation.. c. Calculate: HCl(aq) + Fe 2 O 3 (s) FeCl 3 (s) + H 2 O(l) i. the mass, in grams, of one molecule of H 2 S. (2 marks) ii. the number of hydrogen atoms in five molecules of CH 3 COOH. iii. the concentration (molarity) of the nitrate ions in an aqueous solution which contains 45.0 g of dissolved aluminium nitrate in a volume of ml. (2½ marks) 2013 Chemistry Paper One Question and response book 7

10 d. Octane C 8 H 18 g burns in oxygen to produce carbon dioxide gas and water vapour. What is the change in the total number of moles between reactants and products when 57 g of octane burns completely? (2½ marks) Chemistry Paper One Question and response book

11 Question 13 Oxidation and reduction a. Explain the meaning of the following terms: i. electrolytic cell ii. oxidising agent (oxidant) b. Does the following equation represent an oxidation reduction reaction? Explain your reasoning. 2Al s + Fe 2 O3 s Al 2 O3 s + 2Fe s c. Will a reaction occur spontaneously when a piece of solid copper is placed in a 1.0M Pb 2+ (aq) solution? Explain your reasoning. (2 marks) 2013 Chemistry Paper One Question and response book 9

12 d. An electrochemical cell is constructed using: two beakers 1.0M solutions of Fe 2+ and Pb 2+ clean pieces of Fe and Pb a piece of porous paper which had been soaked in a KNO 3 solution a voltmeter connecting wires. Use the table of standard reduction potentials for half-reactions in the resource book to draw a diagram of the electrochemical cell described above, correctly labelling the: anode and cathode electron flow direction nature and direction of the flow of ions charge on each electrode. (3 marks) Chemistry Paper One Question and response book

13 Question 14 Organic chemistry a. Complete the following table.. General formula Structure which contains three carbon atoms alkenes ketones b. Draw the structure of methyl butanoate. (2 marks) c. Name the organic substance with the following structure. d. What would be the product/s of the following chemical changes? i. ii. HC CH 3 CH 2 CH 2 CH 3 C 3 CH 2 CH 2 CH 2 CH 2 CH 4 g + Br 2 1 CH 3... uv radiation... + C 2 H 5 OH 1 + MnO 4 aq + H aq... e. An organic compound is either an aldehyde or a ketone. List a test and subsequent results that could be used to identify the compound. (2 marks) 2013 Chemistry Paper One Question and response book 11

14 Question 15 Chemical periodicity a. State the trends in the periodic table for the following: i. first ionisation energy of the group 2 elements ii.... atomic radius of the period 3 elements (½ mark)... b. Write the electron configuration for an aluminium atom. (½ mark)... c. The first six ionisation energies of the nitrogen atom, in kj mol 1, are listed in the following table. E E E E E E Explain why: i. E 6 is much greater than E 5... ii. the first ionisation energy (E 1 ) for C (1086 kj mol 1 ) is less than E 1 for N (1400 kj mol 1 ) Chemistry Paper One Question and response book

15 d. Consider the elements lithium and fluorine from the second period of the periodic table and the elements potassium and bromine from the fourth period. Explain why: i. potassium is more reactive than lithium ii. bromine is less reactive than fluorine. (2 marks) 2013 Chemistry Paper One Question and response book 13

16 Question 16 Gases and the atmosphere a. Describe a factor which affects the concentration of ozone in the upper atmosphere. b. List one major gas in the earth s atmosphere and describe how it affects human welfare. c. What is the normal boiling point of a substance whose vapour pressure varies as shown in the graph below? Vapour pressure (kpa) Temp ( C) Chemistry Paper One Question and response book

17 d. Consider the two bulbs below. Bulb A Bulb B He pressure = 1.5 atm volume = 1 L negligible volume in the valve Ne pressure = 1.0 atm volume = 2 L The valve is opened and the contents of the bulbs are allowed to mix, with the temperature being kept constant. What is the final pressure of the gas mixture? (3 marks) 2013 Chemistry Paper One Question and response book 15

18 Question 17 Energy and rates of chemical reactions a. Define the following terms: i. catalyst. ii.. activated complex.. b. State the basic postulates of the collision theory of reactions. (2 marks) c. Given the following data, Ss O 2 g SO 3 g H = kj 2SO 2 g + O 2 g 2SO 3 g H = kj calculate H for the reaction below. Ss + O2 g SO2 g (2 marks) Chemistry Paper One Question and response book

19 d. The following energy diagram shows the energy change in kj mol 1 associated with the use of glucose (C 6 H 12 O 6 ) in body processes. Energy (kj mol ) 1 reactants 180 kj mol kj mol 1 products Reaction coordinate i. Is the reaction exothermic or endothermic? Explain why. ii. Calculate the energy change per gram of glucose Chemistry Paper One Question and response book 17

20 Question 18 Chemical equilibrium a. Define ph. b. Complete the following table. Term Description Example Weak electrolyte c. A dynamic equilibrium is: i. recognised by (1½ marks).. ii. explained by.. d. An equilibrium mixture is established by the addition of concentrated hydrochloric acid to a concentrated solution of cobalt chloride according to the following equation Co H 2 O 6 aq + 4Cl0 aq CoCl4 aq + 6H2 O1 (red) i. Write the equilibrium law expression. (blue) ii. Explain why the mixture becomes more blue when it is warmed Chemistry Paper One Question and response book

21 e. Find the ph of the solution which results when 25.0 ml of 0.12M NaOH is added to 50.0 ml of 0.17M HCl. (4 marks) f ml of 0.25M Mg(NO 3 ) 2 solution is mixed with 25.0 ml of 0.20M NaF solution. Will a precipitate form? K sp for MgF 2 = (4 marks) End of Section 2 End of Part A 2013 Chemistry Paper One Question and response book 19

22 Part B Scientific processes Part B assesses scientific processes based on the topics in the Chemistry Senior External Syllabus 1998 (amended 2006) and practical work undertaken during your study of the subject. Part B has five questions of equal value. Attempt four questions only. If you respond to all five questions, only your first four responses will be assessed. Write your responses in the spaces provided. Suggested time allocation: 40 minutes. Question 1 Chemical periodicity The following information concerning five consecutive elements in the periodic table was collected. The letters assigned to the elements do not show the group order. Elements A B C Properties reacts vigorously with water to liberate a gas which ignites and burns is very unreactive is a monatomic gas sometimes used in light bulbs exists as a gas (composed of diatomic molecules) at room temperature reacts with element A to form a stable solid compound AC D reacts with element C to form the compound DC 2 has a higher boiling point than A is a good conductor of electricity reacts slowly with water E exists as a solid at room temperature reacts with D to form the compound ED burns in air to form a gas with the formula EO 2 (O = oxygen) Determine the group of the periodic table to which each element belongs. You must justify your choices Chemistry Paper One Question and response book

23 Question 2 Oxidation and reduction A student set up an experiment using strips of four different metals (J, L, M and N) which were placed in four different solutions that contained J 2+, L 2+, M 2+ and N 2+ ions respectively (16 beakers in all). The following results were obtained: metal L remained unchanged in all four solutions metal M was coated with another substance when placed in solutions of J 2+ and L 2+ only metal N was coated with another substance when placed in solutions of J 2+, L 2+ and M 2+. Which pair of half-reactions would produce the greatest potential difference in an electrochemical cell? Show all working to explain your choice and include all the appropriate half-equations Chemistry Paper One Question and response book 21

24 Question 3 Organic chemistry An organic compound, W : has a molar mass of 42.0 g burns in pure oxygen to produce carbon dioxide and water only reacts with an equimolar amount of hydrogen bromide to form compound X only. Compound X reacts with sodium hydroxide solution to form compound Y. Compound Y reacts with ethanoic acid (C 2 H 4 O 2 ) in the presence of a suitable catalyst to form compound Z and water. Determine the molecular formulas for compounds W, X, Y and Z. Explain the choices you made Chemistry Paper One Question and response book

25 Question 4 Materials: Properties, bonding and structure A scientist was given unknown pure substances labelled A, B, C and D. She obtained the information below from research and experimentation to develop element profiles. Features A B C D Appearance shiny pale green colour shiny shiny Solubility in water nil slightly soluble nil nil Change on heating in a Bunsen flame produces a white solid no change produces a black solid Melting point C Combine with acid Periodic table group Electrical conductivity generates a large amount of heat slight colour change generates heat, colour change no change no reaction 2 17 unknown unknown good non-conductor good good Tensile strength high nil moderate high a. Use the information from the table to identify one chemical property and one physical property. Chemical: Physical: b. Substances A and B react together to form compound X. Is the bonding in compound X ionic or covalent? Justify your choice. c. Is substance C a metal or a non-metal? Explain your choice. d. Based on the information in the table, which material would be most suitable for making a scuba diving tank? Justify your choice Chemistry Paper One Question and response book 23

26 Question 5 Energy and rates of chemical reactions While researching energy values of fuels, a student designed an experiment to determine the heat of combustion using the apparatus below. Hexane (C 6 H 14 ) of actual heat value (4160 kj mol 1 ) was first used in the burner. Pentane (C 5 H 12 ) was then substituted for the hexane and all other conditions kept constant. thermometer clamp beaker 100 ml of H 2 O flame cloth wick fuel glass bulb Initial water temperature ( C) Burning hexane Final water temperature ( C) Mass of hexane burned (g) Initial water temperature ( C) Burning pentane Final water temperature ( C) Mass of pentane burned (g) Find the actual heat of combustion of pentane, to the highest degree of accuracy available, with due consideration of the information gathered from the hexane investigation. Consider experimental design and the associated errors in addition to the application of numerical calculations Chemistry Paper One Question and response book

27 End of Part B End of Paper One 2013 Chemistry Paper One Question and response book 25

28 Additional response page Chemistry Paper One Question and response book

29 Assessment standards from the Chemistry Senior External Syllabus 1998 (amended 2006) Paper One Criteria Very High Achievement High Achievement Sound Achievement Limited Achievement Very Limited Achievement Knowledge of subject matter A very high ability to recall and apply knowledge of chemistry in simple situations. A high ability to recall and apply knowledge of chemistry in simple situations. A satisfactory ability to recall and apply knowledge of chemistry in simple situations. Limited ability to recall and apply knowledge of chemistry in simple situations. Very limited ability to recall and apply knowledge of chemistry in simple situations. Scientific processes A very high ability to succeed in simple scientific process tasks collecting and organising data, processing information, making simple judgments, communicating information in various contexts, devising and designing simple and/or singlestep investigations. A high ability to succeed in simple scientific process tasks collecting and organising data, processing information, making simple judgments, communicating information in various contexts, devising and designing simple and/or singlestep investigations. A satisfactory ability to succeed in simple scientific process tasks collecting and organising data, processing information, making simple judgments, communicating information in various contexts, devising and designing simple and/or singlestep investigations. Limited ability to succeed in simple scientific process tasks. Very limited ability to succeed in simple scientific process tasks Chemistry Paper One Question and response book 27

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