Chemistry Friday 30 October 2015 Paper One Question and response book

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1 2015 Senior External Examination Chemistry Friday 30 October 2015 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 5 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

2 Planning space

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 A pure substance is found to be a good conductor of electricity in both its solid and liquid phases. The bonding in the substance is A B C D ionic. metallic. covalent network. covalent molecular. Question 2 Which one of the following groups contains the same number of electrons? A Li, Be, B B F, Ne, Na C Cl, Ar, K + D O 2, S 2, P 3 Question 3 Which statement about elements in groups 1 and 2 of the periodic table is correct? A B C D They can only become positively charged and form strong covalent molecules. They can form positive ions because they have loosely held valence electrons. They can only gain electrons to form positive ions or a strong metallic lattice. They form negative ions because they have few valence electrons. 1

4 Question 4 Which change would have the least effect on the rate of reaction between a piece of magnesium metal and 0.01 M hydrochloric acid? A Doubling the temperature of the hydrochloric acid. B Changing the concentration of hydrochloric acid to 2.00 M. C D Using magnesium powder rather than a piece of magnesium. Using tap water rather than distilled water in preparing the hydrochloric acid. Question 5 Gases are more easily compressed than liquids or solids. This is because A B C D gas molecules undergo elastic collisions with the walls of a container. gas molecules move with much greater velocities than the molecules of liquids and solids. the average distance between gas molecules is much greater than that between particles in liquids or solids. attractive forces between gas molecules are much larger than those between particles in solids and liquids. Question 6 Use the table to identify a pair of isotopes. Element Number of protons Number of electrons Number of neutrons W X Y Z A B C D Elements X and W Elements X and Y Elements W and Z Elements W and Y 2

5 Question 7 In an endothermic reaction, the A B C D products will have lower enthalpy. reactants release heat and therefore have lower enthalpy. heat of reaction is negative as the products have lower energy. reactants absorb heat and therefore the reaction container would feel cold. Question 8 Which equation represents an oxidation/reduction reaction? A CaCO 3 s CaO s + CO 2 g B 2Al s + Fe 2 O 3 s Al 2 O 3 s + 2Fe l C MgO s + H 2 Ol Mg 2 + aq + 2OH aq D Al 2 O 3 s + 6H + aq 2Al 3 + aq + 3H 2 Ol Question 9 Which IUPAC name is correct? A B C D 2,2 dimethylpropane 2,2 diethylheptane 2 propylpentane methylpentane Question 10 Which has the lowest hydrogen (hydronium) ion concentration? A B C D 0.1 M HCl(aq) 0.1 M HNO 3 (aq) 0.1 M H 2 SO 4 (aq) 0.1 M CH 3 COOH(aq) End of Section 1 3

6 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. Complete the table below. Definition/description Chemical term i. Formed by the equal sharing of a pair of electrons between two atoms ii. (5 marks) b. 34 Interpreting the information contained in the symbol, answer the following questions. i. The ion shown has the following number of neutrons ii. A different molecular form of the same element in the same physical state iii. Represents one atom of an element iv. Shows the number and types of atoms present in the smallest representative unit of a substance v. Contains two or more substances in any proportion that can be separated by physical means 16 S2... The ion has an electron configuration that is the same as the element called... c. Complete the table below by writing the name or formula of each substance listed. Name hydrofluoric acid iron(ii) sulfate Formula SO 3 OH 4

7 d. Complete the table below. Shape of covalent molecule Example i. Planar trigonal ii. Tetrahedral e. State the attractive forces (type and location) present in: i. Sodium chloride dissolved in water ii. Liquid oxygen 5

8 Question 12 Reacting quantities and chemical analysis a. Explain the following term: Avogadro s number (6.02 x ) b. Write the balanced equation for the reaction that takes place when solid iron reacts with oxygen gas to form solid iron(iii) oxide. c. How many ammonium ions are present in 3.0 moles of (NH 4 ) 2 S? (1½ marks) d. What mass of silver is present in 3.40 g of AgNO 3? e. A 2.80 L sample of a gaseous organic compound at STP is found to have a mass of 7.00 g. Calculate the molar mass of the compound f. 200 ml of Na 2 SO 4 (aq) is reacted with an excess of BaCl 2 (aq) and 2.6 g of BaSO 4 (s) is precipitated. What is the concentration (molarity) of the Na 2 SO 4 solution? (2½ marks) 6

9 Question 13 Oxidation and reduction a. Complete the following: A reducing agent (reductant) is a substance in a redox reaction that electrons. In that reaction, the reducing agent is b. Copper(II) oxide undergoes a redox reaction with carbon to produce copper metal and carbon monoxide gas, as shown in the equation below. CuO s + Cs Cu s Which substance is the reductant in this reaction? +... CO g c. A galvanic cell is constructed from two half cells. Half cell 1: a nickel electrode in a solution of 1.0 M nickel nitrate Half cell 2: a zinc electrode in a solution of 1.0 M zinc nitrate A diagram of the cell is given below. (½ mark) voltmeter Ni(s) salt bridge Zn(s) 2+ Ni (aq) Zn 2+ (aq) Half cell 1 Half cell 2 i. On the diagram, show the direction in which electrons will flow in the galvanic cell. ii. Write the equation for the half reaction that takes place at the anode of the cell. iii. Calculate the potential difference (voltage) of the cell. 7

10 d. Three metals, J, K and L, were tested to find out which was the most reactive. Samples of each metal were placed, one at a time, in solutions of the ions as shown. The following results were obtained: J(s) K(s) L(s) J 2+ solution no reaction solid forms K 2+ solution solid forms solid forms L 2+ solution no reaction no reaction Which metal was the most reactive (strongest reductant)?... Explain your response. (½ mark) e. Copper can be purified by electrolysis using a cell as shown. source of direct current electrode made from impure copper electrode made from pure copper solution of copper(ii) sulfate A current of 15.0 A is passed through the solution for 5 hours. Calculate the mass of pure copper that would be deposited

11 Question 14 Organic chemistry a. Complete the table below. Definition/description Chemical term i. An organic compound containing only carbon and hydrogen in which all carbon atoms are joined by single bonds ii. A very large molecule formed by the covalent bonding of repeating small molecules b. Name the organic substance with the following structure. CH 3 O CH 2 CH 2 CH 2 O C CH c. Draw the structural formula for any structural isomer of 3 methyl 2 pentene. d. Citric acid has the following structural formula. OH O C O C OH CH 2 C CH 2 OH OH C O i. On the diagram, circle any alcohol functional groups that are present. ii. Name any other functional groups that are present. 9

12 e. Complete the table below. Reaction Type of reaction i. Ethanol reacts with acidified Cr 2 O 7 2 (aq) ii. Chlorine reacts with ethene iii. Methane reacts with bromine in the presence of UV radiation iv. Methanol reacts with propanoic acid (conc H 2 SO 4 catalyst) 10

13 Question 15 Chemical periodicity a. Explain how an element s outer electron configuration is related to its group in the periodic table b. Write the ground state electron configuration of aluminium.... c. Name the element which: i. is the heaviest inert gas which has no d electrons... ii. is the lightest atom which contains a half-filled p orbital... iii. has a 2+ charged ion with the same electron configuration as He... iv. has a 2 charged ion with the same electron configuration as the ground state of Ne... v. is found in group 2 and period 3 of the periodic table... vi. is the most electronegative element in group (3 marks) d. The K + ion has the same number of electrons as the Cl ion but the ionic radii are different. Explain why

14 Question 16 Gases and the atmosphere a. Explain the meaning of: i. ideal gas behaviour.. ii.. diffusion of gases.. b. A 20.0 L container holds 2.0 g of hydrogen gas and 3.0 g of helium gas. Find the partial pressure exerted by the hydrogen gas if the total pressure is 50 kpa c. 5.0 L of chlorine gas at 50.0 C exerts a pressure of 100 kpa. What mass of gas is present?

15 Question 17 Energy and rates of chemical reactions a. State the law of conservation of energy b. Explain the difference between the terms enthalpy and entropy c. Use collision theory to explain how the temperature of a system influences the rate of reaction

16 d. Methane (CH 4 ) burns in oxygen to form carbon dioxide gas and water vapour. Use the applicable bond energies from the following table to calculate the heat of combustion of methane. Bond energies (kj mol 1 ) H H 436 O H 463 H Cl 432 O O 146 H Br 366 O=O 498 H I 299 N H 391 C C 348 C H 413 C=C 610 C O 358 C C 835 C=O e. The first step in the manufacture of nitric acid involves the burning of ammonia (NH 3 (g)) in oxygen (O 2 (g)) to form nitrogen dioxide (NO 2 (g)) and water (H 2 O(l)). Use the standard enthalpies of formation in the following table to calculate H for the reaction. Compound H (kj mol 1 f ) NH 3 (g) 0 46 NO 2 (g) 0 34 H 2 O(l)

17 Question 18 Chemical equilibrium a. Explain the following term: saturated solution b. Apply relevant equilibrium principles to explain the Haber process (3 marks) c. The ph of a carbonated drink was found to be 3.1. What is the hydrogen (hydronium) ion concentration?

18 d. The table below shows the molar solubilities of several ionic compounds in pure water, in 1.0 M sodium sulfate solution and in 1.0 M barium nitrate solution. Solubility (mol L 1 ) Compound In pure H 2 O In 1.0 M Na 2 SO 4 In 1.0 M Ba(NO 3 ) 2 SrSO x x x 10 4 PbSO x x x 10 4 BaSO x x x 10 9 PbF x x x 10 3 BaF x x x 10 3 BaCO x x x 10 9 SrCO x x x 10 5 Write a conclusion regarding solubility patterns that may be inferred from this data. Clearly justify your response e. The solubility of aluminium hydroxide is 1.2 x 10 3 g L 1. Calculate the value of K sp

19 f. Chlorine gas reacts with hydrogen gas to form hydrogen chloride gas according to the following equilibrium: Cl 2 g + H 2 g 2HCl g K eq = 3.0 Chlorine and hydrogen (both at 3.0 M initial concentration) were added to an empty reaction container. Develop an expression which could be used to find the equilibrium concentration of hydrogen chloride End of Section 2 End of Part A 17

20 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 Using information from the table below and the resource book, identify substances A, B, C and D from the following list: aluminium calcium carbonate copper copper(ii) sulfate graphite iodine mercury octane sodium chloride Electrical conductivity in the solid state Electrical conductivity in the liquid state Solubility in water Phase at 25 C Colour at 25 C A nil conducts high solid blue B conducts conducts insoluble solid silver C nil nil insoluble liquid colourless D nil nil low solid white Substance A Name... Reason

21 Substance B Name... Reason Substance C Name... Reason Substance D Name... Reason

22 Question 2 Gases and the atmosphere After reading a textbook, a student formulated the hypothesis that different liquid fuels have different heats of combustion. The student designed a scientific investigation to test this hypothesis. a. Draw a labelled diagram of the apparatus used. b. In point form, describe the method employed c. What data would support the hypothesis? d. What data would not support the hypothesis? e. Identify a possible source of error in the experiment

23 Question 3 Energy and rates of chemical reactions Hydrogen gas and gaseous iodine react to form hydrogen iodide according to the following equation. H 2 g + I 2 g 2HI g The graph below shows the concentration of HI(g) formed over time. The reaction was carried out at 40 C in a 250 ml vessel. Concentration of HI (ml) Time (s) a. Use collision theory to explain the decreasing slope of the curve as the reaction progresses b. Sketch a new curve on the graph to indicate how the concentration of HI(g) formed as the reaction progresses would change if the concentration of I 2 (g) in the vessel was increased and the temperature was kept at 40 C. Label as Plot B. c. Sketch a new curve on the graph to indicate how the concentration of HI(g) formed as the reaction progresses would change if the temperature of the original system was decreased to 30 C. Label as Plot C. 21

24 Question 4 Reacting quantities and chemical analysis A chemist analyses several samples of lead sulfide collected from different locations for the masses of sulphur and lead present. The results are given below: Sample number Mass of lead (g) Mass of sulfur (g) ? a. Graph the first six results, plotting mass of Pb against mass of S. 22

25 b. Predict the mass of lead in sample c. Based on the experimental data, determine the molar ratio of lead to sulfur d. On the basis of the molar ratio determined above, is the Pb 2+ ion or the Pb 4+ ion involved in the reaction?... 23

26 Question 5 Chemical equilibrium In solution, pale yellow-coloured Fe 3+ (aq) and colourless SCN (aq) form an equilibrium with red FeSCN 2+ (aq). Fe 3 + aq + SCN aq FeSCN 2 + aq H is negative a. A student investigates this reaction using separate samples of an equilibrium mixture in which significant quantities of Fe 3+, SCN and FeSCN 2+ are present. In each case, changes are made as indicated in the table below. Complete the table by ticking in the appropriate boxes to indicate the effect of each change on i. the intensity of the red colour of the solution ii. the concentration of Fe 3+ (aq) once the new equilibrium has been established. Change to the equilibrium Sample 1: 1 drop of a concentrated solution of Ag + (aq) is added, which forms a AgSCN precipitate i. Colour at new equilibrium compared with initial equilibrium ii. [Fe 3+ ] at new equilibrium compared with initial equilibrium less red more red decreased increased Sample 2: 1 drop of a concentrated solution of Fe 3+ (aq) is added Sample 3: 1 drop of a concentrated solution of HPO 4 2 (aq) is added, which forms colourless FeHPO 4 + (aq) b. The graph below represents the initial concentration of the ions at equilibrium. Sketch the changes that would be expected to occur to these concentrations if the temperature of the equilibrium mixture was increased to a new, constant value. Concentration (M) FeSCN 2+ SCN Fe 3+ initial equilibrium Time (s) final equilibrium End of Part B End of Paper One 24

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28 Additional response page

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 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. 27

30 The State of Queensland (Queensland Curriculum and Assessment Authority) 2015 Copyright enquiries should be made 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