Chemistry Friday 7 November 2014 Paper One Question and response book

Transcription

1 2014 Senior External Examination Chemistry Friday 7 November 2014 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 Resource book Paper One Part A Multiple-choice response sheet Equipment allowed QCAA-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 4 Attach barcode here Number of books used Supervisor use only Supervisor s initials QCAA 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. For all Queensland schools

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3 Part A Knowledge of subject matter Part A assesses knowledge of subject matter and its simple application based on the eight 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 worth 1 mark each. 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 is a correct classification? Element Compound Mixture A air carbon dioxide copper sulfate B nitrogen steel sodium chloride C helium iron ore tap water D distilled water diamond the ocean Question 2 The production of nitrous oxide, NO, proceeds according to the equilibrium equation: 4NH 3 g + 5O 2 g 4NO g + 6H 2 Og H = 907 kj Which of the following would favour the production of a high yield of NO? A B C D low pressure, removal of NO low pressure, high temperature high pressure, low temperature oxygen addition, high temperature 1

4 Question 3 The molecule represented by the structural formula below is the alarm pheromone produced by honey bees. CH 3 O This molecule could be classified as CH CH 2 CH 2 O C CH 3 CH 3 A B C D an ester. a ketone. an alkane. a carboxylic acid. Question 4 The element magnesium has an atomic mass of This means A B C D each atom of magnesium weighs 24.3g. one magnesium atom is four times as heavy as one carbon atom. each atom of magnesium has a mass of exactly 24.3 atomic mass units. one magnesium atom is about 24 times as heavy as one hydrogen atom. Question 5 The formula for strontium iodate is Sr(IO 3 ) 2. What would be the formula for sodium iodate? A NaIO 3 B Na(IO 3 ) 2 C Na 2 IO 3 D Na 2 (IO 3 ) 2 2

5 Question 6 A section of the periodic table has had the chemical symbols replaced by letters. Q R S T Which element is most likely to exist as a lattice structure held together by covalent bonds? A B C D Q R S T Question 7 Which of the following substances would you expect to be the least soluble in water? A ammonia H N H H B hydrogen chloride H Cl C chlorine dioxide O Cl O Cl D carbon tetrachloride Cl C Cl Cl 3

6 Question 8 As a person dives into the sea the pressure of gas in their lungs changes from 100 kpa to 150 kpa. If their lungs initially held 6 L of gas, what is the new volume at constant temperature? A B C D 3 L 4 L 6 L 9 L Question 9 The following energy profile relates to the two reactions: 2Cu s + O 2 g 2CuO s H = 312 kj 1 2Cu s + - O = 170 kj 2 2 g Cu 2 Os H 2Cu s + O 2 g H = 170 kj enthalpy 1 2 Cu 2 Os + - O 2 g H = 312 kj 2CuO s What is the value of H kj for the reaction below? A +284 B +142 C 142 D 284 2CuO s 1 Cu 2 Os + -O g 2 2 4

7 Question 10 An electrochemical cell was set up as shown in the diagram below. connecting wire zinc electrode lead electrode salt bridge zinc nitrate solution lead nitrate solution For the cell shown, A B C D there will be no electron flow in the wire. electrons will flow from the lead electrode to the zinc electrode. electrons will flow from the zinc electrode to the lead electrode. electrons will flow through the salt bridge between the two solutions. End of Section 1 5

8 Section 2 Short response Section 2 has eight questions worth 70 marks in total. Attempt all questions. Write your responses in the spaces provided. Show all working. If you need more space for a response, continue at the back of this book. Label any continued response with the question number. Question 11 Materials: Properties, bonding and structure a. Explain the following terms: i. electron shell.. ii.. electron configuration... b. Naturally occurring chlorine exists as the two isotopes and. This indicates that the two nuclei of chlorine have: i. the same ii. different Cl Cl c. Explain why CO 2 vaporises at 78.5 C while SiO 2 melts at 1700 C. (2 marks) 6

9 d. Draw Lewis diagrams for the following molecules and give the shape of each molecule. Molecule Lewis diagram Shape of molecule BF 3 C 2 H 2 e. The diagrams below represent four different types of substances. (2 marks) A. B. C. D. Match the diagram with the type of substance. Metal Ionic solid Covalent network solid Covalent molecular solid... f. Give the formula for the hydrogen carbonate ion. (2 marks)... g. Name the substance that is represented by the formula P 2 O

10 Question 12 Reacting quantities and chemical analysis a. Explain the following term: mass spectroscopy parent ion b. Balance the following equation: Na 3 PO 4 aq + Pb NO 3 2 aq NaNO 3 aq + Pb 3 PO 4 2 s c. Calculate: i. the mass of 0.1 moles of sodium chloride (2 marks).. ii.. the molar mass of a gas which has a density of 1.95 g L 1 at STP

11 d. A student is given a 1.0 L bottle which contains a 6.0M solution. How would she prepare a 250 ml sample of 0.8M concentration? (2 marks) e. Ammonia can be prepared by the following reaction: N 2 g + 3H 2 g 2NH 3 g How many litres of ammonia will be produced if 1.0 L of nitrogen is reacted with excess hydrogen? (2 marks) f. The world s oceans are estimated to contain 1.5 x L of water. If 5.0 moles of sugar were distributed uniformly throughout the oceans, how many of these sugar molecules would be in a cup of seawater (250 ml)? (2 marks) 9

12 Question 13 Oxidation and reduction a. Explain the following term: anode b. Determine the oxidation number of Mn in KMnO c. Identify the oxidising agent in the following chemical reaction. Explain your choice Cu s + NO 3 aq + H aq Cu aq + NO2 g + H 2 Og (1½ marks) d. Draw a labelled diagram to describe the chemical processes involved in obtaining pure copper from an impure sample. Include equations in your response. (2 marks) 10

13 e. A galvanic cell was set up as shown in the diagram below. A piece of copper and a piece of platinum were placed in a solution of CuC1 2 (aq) and connected by a wire. Chlorine gas was bubbled through the solution over the piece of platinum.. Cu Pt C l 2 gas Cu 2+ Cl i. Identify the anode in the above cell. Explain your response. (1½ marks) ii. Calculate the potential difference of the above cell. 11

14 Question 14 Organic chemistry a. Explain the following terms: i. functional group.. ii.. elimination polymerisation... b. Name the organic substance with the following structure. H O C CI HC 3 C CH CH 2 CH 2 CH 3 CI c. A student incorrectly named the following two compounds. Write the correct names according to the IUPAC naming system. Incorrect name IUPAC name i. 3,3 dimethyl 4 methylpentane ii. 2 ethylpropane (2 marks) 12

15 d. Complete the following table. General formula Structure which contains four carbon atoms carboxylic acids amines (2 marks) e. A student is given an organic compound that is either an alkane or an alkyne. State a test and subsequent results that could be used to classify the compound. 13

16 Question 15 Chemical periodicity a. On the diagram below, identify the s, p, d and f block groups of elements. b. Name an element which: (2 marks) i. has a half-full s subshell in its ground state electron configuration... ii. requires 3 additional electrons to obtain a full outer shell... iii. has a very low first ionisation energy... iv. forms an acidic oxide... v. has the same group number and period number... vi. is similar chemically to the element with ten electrons... c. Explain the trend in atomic radius displayed by the period 2 elements of the periodic table. (3 marks)

17 Question 16 Gases and the atmosphere a. Describe, using the particle theory, what happens when an air hose is used to inflate a bicycle tyre. b. Explain the concept of vapour pressure and one factor on which it depends. c. 8.4 g of nitrogen gas is present in a sealed 1.5 L container which is held at a temperature of 40 C. What pressure is exerted? (2 marks) 15

18 d. 500 ml of nitrogen gas is collected over water at 25 C at a pressure of kpa. N (g) 2 delivery tube H0 2 The nitrogen gas is not pure but is mixed with water vapour which exerts a vapour pressure of 2.8 kpa at that temperature. Find the volume that nitrogen alone would occupy if the conditions were at STP. (2 marks) 16

19 Question 17 Energy and rates of chemical reactions a. Define the following terms: i. exothermic reaction ii. reaction mechanism b. Gases A and B react to form gas C according to the reaction coordinate diagram below. 100 Potential energy (kj/mol) 0 Reaction coordinate i. Is the reaction exothermic or endothermic? Explain your response. ii. Would you expect this reaction to occur rapidly at room temperature? Explain your response. iii. Suggest a method by which the reaction rate could be increased. 17

20 c. As a substance melts its temperature remains constant, even though heat is still being applied. Describe the energies involved in the phase change. d. Use the standard enthalpies of formation to calculate the enthalpy change associated with the decomposition of calcium carbonate, CaCO 3 s CaO s + CO 2 g Substance H f (kj mol 1 ) CaCO 3 (s) 1207 llllcao(s) 636 lllco 2 (g) 393 (2 marks) 18

21 Question 18 Chemical equilibrium a. Consider a gas-fuelled bunsen burner producing a constant amount of heat. Has equilibrium been established? Explain. b. i. Use the Lowry Brönsted theory of acids and bases to define an acid. ii. Use the Lowry Brönsted theory to identify the conjugate acid-base pairs in the following equation. 2 + HSO 4 aq + NH3 g SO 4 aq + NH4 aq c. i. List two physical properties of acids. ii. Describe a chemical reaction of bases. d. Determine the ph of a solution which contains 1 x 10 9 moles of OH ions in a volume of 0.5 L. (2 marks) 19

22 e. The Ksp of BaCO 3 at 25 C is 8.1 x Calculate the mass (in grams) of barium carbonate that will dissolve in 0.5 L of solution at 25 C. (2½ marks) f. The following equilibrium is established by reacting PC1 3 (g) and Cl 2 (g) in a closed container. PCl 3 g + Cl 2 g PCl 5 g The initial concentrations of PCl 3 (g) and Cl 2 (g) are both 2.0M and the concentration of PCl 5 (g) is found to be 0.5M when equilibrium is established. Find the value of the equilibrium constant. (2½ marks) End of Section 2 End of Part A 20

23 Part B Scientific processes Part B assesses scientific processes based on the eight 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 Materials: Properties, bonding and structure A student leaves a solution unlabelled in the laboratory. It is known to contain one of the following cations: Pb 2+, Sr 2+, Ba 2+, Mg 2+, or Ca 2+. He then tests samples of the unknown solution with 1.0M solutions of Na 2 SO 4, NaCl and NaOH, to obtain the following results: Test Result SO 4 2 the solution is added a white precipitate forms the Cl solution is added the OH solution is added a white precipitate forms a white precipitate forms Use the information provided above and the resource book to determine which cation is present in the unknown solution. Fully explain your reasoning

24 Question 2 Gases and the atmosphere Below are the rough laboratory notes of a chemistry student investigating the relationship between volume and pressure of a gas. R. T 23. ºC * 40.0 kpa 61.9 ml V of Flask * kpa 19.0 ml * kpa ml * 50.0 kpa 49.8 ml * kpa * kpa 21.0 ml 33. 0mL syringe * kpa 23.3 ml a. Organise the data from the investigation into a table. b. On the graph paper provided on the next page, plot a graph of pressure against volume. c. Identify any anomalous data by circling the data point on the graph. d. Use the graph to determine the volume of the apparatus when the pressure was kpa. 22

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26 Question 3 Energy and rates of chemical reactions The reaction of solid calcium carbonate with hydrochloric acid can be described by the equation: CaCO 3 s + 2HCl aq CaCl 2 aq + CO 2 g + The rate of this reaction can be studied by continuously measuring the mass of the reaction mixture in an open vessel. Case X deals with 10.0 g of small calcium carbonate crystals with a g solution containing 0.25 mol of hydrochloric acid. Case Y deals with 10.0 g of large calcium carbonate crystals with a g solution containing 0.25 mol of hydrochloric acid. The results of the experiments are displayed in the following graph: 210 H 2 Ol Mass (grams) of contents of flask Case X Case Y Time (minutes) a. Explain why this method can be used to follow the rate of the reaction. b. Which reactant is in excess? Explain your response. c. What effect does crystal size have on the rate of reaction? Explain your response. d. Suggest a method for following the rate of reaction if the flask was closed. 24

27 Question 4 Reacting quantities and chemical analysis Sulfuric acid reacts with thio (sodium thiosulfate) producing a precipitate of sulfur. Samples of 10 ml of 0.1M thio were placed in similar tubes and varying quantities of 0.2M acid were added. The sulfur precipitate was allowed to settle and its depth measured. The results are given below. Volume of 0.2M H 2 SO 4 added (ml) Depth of precipitate (mm) In what molar proportions do thio and acid react? Explain your response

28 Question 5 Chemical equilibrium Carbon monoxide reacts with fluorine to produce carbon oxyfluoride as shown in the equation: CO g + F2 g COF2 g A scientist studying this reaction measured the concentration of each of these gases in a sealed 2.0 L reaction vessel over a period of time. The results are shown below. 0.5 COF 2 COF 2 Concentration (mol L ) F 2 F CO CO Time (minutes) a. At what time did the reaction first reach equilibrium? b. What change was made by the scientist at t = 15minutes? Explain the variation in concentration of the three substances. c. At t = 30minutes, the temperature of the reaction vessel was decreased. Is the reaction exothermic or endothermic? Explain. End of Part B End of Paper One 26

29 Additional response page

30 Additional response page

31 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 single-step 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 single-step 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 single-step investigations. Limited ability to succeed in simple scientific process tasks. Very limited ability to succeed in simple scientific process tasks. 29

32 The State of Queensland (Queensland Curriculum and Assessment Authority) 2014 Copyright protects this material. Copyright in the Senior External Examination is owned by the State of Queensland and/or the Queensland Curriculum and Assessment Authority. Copyright in some of the material included in the paper is owned by third parties. Except as permitted by the Copyright Act 1968 (Cwlth), reproduction by any means (photocopying, electronic, mechanical, recording or otherwise), making available online, electronic transmission or other publication of this material is prohibited without prior written permission of the relevant copyright owner/s. The Queensland Curriculum and Assessment Authority requires to be recognised as the source of the Senior External Examination and requires that its material remain unaltered. Enquiries relating to copyright in this material, which is owned by the State of Queensland or the Queensland Curriculum and Assessment Authority, should be addressed to: Manager Publishing Unit Queensland Curriculum & Assessment Authority PO Box 307, Spring Hill QLD 4004 Australia Level 7, 154 Melbourne Street, South Brisbane T F