Chemology unit 3 exam PDF

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1

CHEMOLOGY EDUCATION SERVICES Name:______________________

CHEMISTRY - Year 12 UNIT 3 TRIAL EXAM – 2007 Time allowed:

1 hour

30 minutes

QUESTION AND ANSWER BOOKLET Structure of booklet Section A B

Number of questions

Number of questions to be answered

21 multiple choice Questions 7

21 multiple choice Questions 7

Directions to students Materials

Question and answer booklet of 23 pages. Answer sheet for multiple choice Questions An approved calculator may be used. Data Pages (24, 25) The Task

Pleasure ensure that you write your name on the multiple choice answer sheet and this answer booklet. Answer all Questions from Section A, which should be answered on the sheet provided. Answer all questions from Section B, which should be answered in this booklet in the spaces provided. There is a total of 85 marks available.All answers should be written in English.

ã CHEMOLOGY EDUCATION SERVICES P O BOX 477 MENTONE 3194 Telephone/Fax 9587 2839 or 0412 405 403 or For more resources visit: www.chemology.com.au

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0425 749 520

©Chemology Chemistry Unit 3 Trial Exam - 2007

2 SECTION A Specific instructions for Section A Section consists of 22 multiple choice Questions. Section A is worth approximately 28% of the marks available. You should spend about 30 minutes on this section. Choose the response that is correct or best answers the question, and mark your choice on the multiple choice answer sheet provided. No credit will be given for a Question if two or more letters are marked for that Question. Marks will not be deducted for incorrect answers and you should attempt every Question.

Question 1 The diagram below shows a chromatogram obtained from Thin Layer Chromatography. The sample was originally placed at X.

A B C

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Solvent front

X

Which one of the following is true? A B C D

Component A is most strongly adsorbed. Component B has an Rf value of 0.70 Component C is the least strongly adsorbed. Position X must be originally below the solvent.

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©Chemology Chemistry Unit 3 Trial Exam - 2007

3 A particular lighter fluid contains three hydrocarbons. Their boiling temperatures are listed in the table below: Name of Hydrocarbon Boiling Temperatures(°C) heptane

98.4

hexane pentane

68.7 36.1

A sample of the lighter fluid was analysed using gas-liquid chromatography (GLC). The order in which these hydrocarbons were detected at the end of the column is most likely to be A. B. C. D.

heptane, hexane, pentane. hexane, pentane, heptane. pentane, heptane, hexane. pentane, hexane, heptane.

Question 3 A definition for a Brønsted-Lowry acid should contain which of the following phrases? A. B. C. D.

The donation of H฀+ The donation of OH-. The acceptance of H฀+ The acceptance of OH-

Question 4 Which of the following substances is best analysed by gas chromatography? A. B. C. D.

Calcium in milk. Proteins present in wine. Carbon monoxide in the atmosphere. Sugar content of soft drinks.

Question 5

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4 A solution of KMnO4 is standardized using oxalic acid H2C2O4, ฀฀฀฀according to the following equation:

The titration of 0.134g of oxalic acid required 24.70mL of KMnO4 solution. What is the molarity of the KMnO4 solution? A. 5.96 B. 1.49 C. 2.41 D. 6.03

x ฀10-4 M x ฀10-3 M x ฀10-2 M x ฀10-2 M

Question 6 Which statement explains why catalysts are often used in chemical reactions? A. B. C. D.

Catalysts increase the rate of reactions. Catalysts increase the yield of products of reactions. Catalysts increase the purity of products of reactions. Catalysts increase the activation energies of reactions.

Question 7 Oxalic acid dihydrate is a pure, stable, crystalline substance. Which of the following describes one of its uses in acid-base titrations? A. buffer B. primary standard C. chemical indicator D. stoichiometric indicator

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©Chemology Chemistry Unit 3 Trial Exam - 2007

5 At a given temperature a sample of pure water has a pH = 8.10. Which of the following is true?

Question 9 Consider the reaction:

What is the rate of Al consumption in mol / min if 0.98g Cu is produced in 2.5 minutes? A. 4.1 x ฀10-3 mol / min B. 6.2 x ฀10-3 mol / min C. 9.3 x ฀10-3 mol / min D. 3.9 x ฀10-3 mol / min

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©Chemology Chemistry Unit 3 Trial Exam - 2007

6

Question 10 Which of the following are the values for the activation energy ฀Ea change in enthalpy ฀ΔH ฀฀for the reverse reaction?

Question 11 Some brown coloured nitrogen dioxide was allowed to reach equilibrium according to the reaction below N2O4(g) 2NO2(g) If the reaction mixture was contained in a vessel of variable volume and the volume was doubled, then which of the following is correct when equilibrium has be attained. A. The value of the equilibrium constant would double. B. The intensity of the brown colour would be less. C. The reaction would move backward. D. The concentration of NO2 would be greater than before the volume was halved.

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©Chemology Chemistry Unit 3 Trial Exam - 2007

7 Question 12 Consider the following diagram for the equilibrium system: N2O4(g) 2NO2(g) ΔH = +280 kJ mol-1

Which of the following stresses was applied at time t1? A. [NO2 ฀] ฀was increased. B. [N2O4฀] was decreased. C. Temperature was increased. D. Temperature was decreased.

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©Chemology Chemistry Unit 3 Trial Exam - 2007

8 Question 13 Styrene is manufactured as follows: C6H5CH2CH3 (g)

à

C6H5CHCH2 (g) + H2 (g)

ΔH = -123 kJ mol-1

Which of the following describes the temperature and pressure needed for the maximum yield of styrene?

Question 14 What is the mass of NaOH required to prepare 100.0mL of NaOH฀ (aq) ฀฀that has a pH =13.62 ? A. 0.38g B. 0.42g C. 1.67g D. 2.40 x 10-14 g

Question 15 When 10ml of 0.1M HCl solution is mixed with 10ml of 0.1M Ba(OH)2 solution, the final pH is closest to: A. B. C. D.

1.3 12.7 7.0 12.4

Question 16 For more resources visit: www.chemology.com.au

©Chemology Chemistry Unit 3 Trial Exam - 2007

9 –1

–1

Acid X is 0.1 mol L hydrochloric acid. Acid Y is 1.0 mol L ethanoic acid. How does acid X compare with acid Y? A. B. C. D.

X is weaker and more dilute than Y. X is stronger and more dilute than Y. X is weaker and more concentrated than Y. X is stronger and more concentrated than Y.

Question 17 Which statement best describes the equivalence point in a titration between a strong acid and a strong base? A. The point at which the first sign of a colour change occurs B. The point at which equal moles of acid and base have been added together +

–

C. The point at which equal moles of H ions and OH ions have been added together. D. The point at which the rate of the forward reaction equals the rate of the reverse reaction. Question 18 The numerical value of Ka for HCN is 6.2 x 10-10 M. The pH of a 0.010M solution of HCN is A. B. C. D.

2.0 5.6 7.0 9.2

Question 19 Which is the main industrial source of ethene? A. B. C. D.

Ethanol Glucose Petroleum Polyethylene

Question 20

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©Chemology Chemistry Unit 3 Trial Exam - 2007

10 A carboxylic acid forms a methyl ester of molecular formula, C4H8O2 . The acid is A. B. C. D.

methanoic acid ethanoic acid propanoic acid butanoic acid.

Question 21 How many isomers are there for C3H6Cl2? A. B. C. D.

3 4 5 6

END OF SECTION A

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11 SECTION B Specific Instructions for Section B Section B consists of 7 short answer questions (question 1 to 7). You must answer all of these questions. The section is worth 64 marks or approximately 75% of the total. You should spend approximately 60 minutes on this section. The marks allocated and suggested time, are at the end of each question. Questions should be answered in the spaces provided in this booklet. You should * give simplified answers with the appropriate number of significant figures. Unsimplified answers will not receive full marks. * Show all working in your answers to numerical problems. No marks can be given unless accompanied by working. * make sure all chemical equations are balanced and that formulas for individual substances include an indication of state. Eg H2(g) , NaCl (s).

Question 1 (5 marks) (a) Calculate the pH of a 0.2M solution of a hydrochloric acid, HCl, solution. (1 mark) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ (b) Calculate the pH after 20 mL of 0.01M sodium hydroxide, NaOH is added to 50 mL of 0.2M hydrochloric acid. Include a balanced chemical equation in your answer. (4 marks) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

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©Chemology Chemistry Unit 3 Trial Exam - 2007

12 Question 2 (6 marks) Atomic absorption spectroscopy was used to analyse a set of standard solutions of copper. The results are presented in the table.

(a) Draw an appropriate graph of the data.

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[2 marks]

©Chemology Chemistry Unit 3 Trial Exam - 2007

13 (b) Two samples of a garden fungicide were analysed for their copper content using the following method: 20ml of the fungicide was added to 100ml of water and the absorbance measured as shown in the table.

i)

Explain the significance of using a copper lamp as the light source in this analysis. [2 marks]

________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

ii)

Determine the concentration of copper in the fungicide in sample 1. (2 marks) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

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14 Question 3 (13 marks) Aspirin is a common pain-relieving drug. The following procedure was used to determine the percentage, by mass, of aspirin in aspirin tablets: Step 1 Four aspirin tablets, each of mass 300 mg, were crushed and added to 30.0 mL of 1.00M NaOH solution. Excess NaOH remained after the reaction was complete. Step 2 The excess NaOH was titrated with 0.50M H2SO4 solution from a burette. (a) Suggest a reason why the aspirin tablets were crushed in Step 1.

(1 mark)

________________________________________________________________________ ________________________________________________________________________ (b) The burette used in this titration was prepared carefully, to ensure that the results were accurate. State two steps that would have been followed in the preparation of the burette, and state why each step was necessary to ensure accuracy. (4 marks) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

(c) Bromothymol blue was used as an indicator for the titration. Bromothymol blue is yellow in acidic solution and blue in basic solution. State the colour that would indicate the end-point of the titration. (1 mark) ________________________________________________________________________

Question 3 continued

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15 Credit will be given for the correct use of significant figures in answers to part (d). (d) (i) Calculate the number of moles of NaOH solution added to the aspirin tablets in Step 1. (1 mark) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ The equation for the titration reaction in Step 2 is shown below: 2NaOH (aq) + H2SO4 (aq)

à

Na2SO4 (aq) + 2H2O (l)

In one titration 23.7 mL of H2SO4 was required to react completely with the excessNaOH. ii) Calculate the number of moles of H2SO4 needed to neutralise the excess NaOH. (1 mark) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

iii) Hence, calculate the number of moles of NaOH that reacted with the aspirin tablets in Step 1. (2 marks) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

Question 3 continued

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©Chemology Chemistry Unit 3 Trial Exam - 2007

16 iv) Aspirin reacts with NaOH in a 1:1 mole ratio. Use this information to calculate the total mass of aspirin in the tablets and hence the percentage, by mass, of aspirin in each tablet. The molar mass of aspirin is 180g mol–1. (3 marks) ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________

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17 Question 4 (13 marks) (a) Methanol is used to make a compound with the structural formula shown in the diagram below:

a) Write the systematic name of this compound.

(1 mark)

_______________________________________________________________ b) Draw the structure and name the other compound that is reacted with methanol to make the above compound. (2 marks)

c) Methanol is produced by the reaction of carbon monoxide with hydrogen, as shown in the equation below:

Equilibrium is established in a closed system under high pressure in the presence of a catalyst. (i)

State two reasons for using high pressure in this system.

(2 marks)

________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ Question 4 continued

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©Chemology Chemistry Unit 3 Trial Exam - 2007

18 (ii)

State why a closed system is necessary to establish equilibrium. (1 mark)

________________________________________________________________ ________________________________________________________________

At a particular temperature, the value of K for this equilibrium is 0.02. (iii) Write the equilibrium expression for this reaction.

(1 mark)

At a different temperature, CO and H2 were placed in a 1.0 L reaction container and allowed to reach equilibrium. The data collected are shown in the table below:

iv) Determine the value of the equilibrium constant at this temperature. (3 marks) ________________________________________________________________ ________________________________________________________________ ________________________________________________________________ ________________________________________________________________

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©Chemology Chemistry Unit 3 Trial Exam - 2007

19 v) The system was at equilibrium between 0 – 5 minutes. At 5 minutes the volume of the mixture was halved and equilibrium re-established at 10 minutes. Show on the graph below the change in the concentrations of CO and CH3OH between 0 – 15 minutes.

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20 Question 5 (4 marks) Consider the reaction: 2 Zn (s) + O2 (g)

à 2 ZnO (s)

State two different methods that would increase the rate of this reaction. Explain each in terms of collision theory. Method 1:

(2 marks)

________________________________________________________________ Explanation: ________________________________________________________________ ________________________________________________________________ ________________________________________________________________

Method 2:

(2 marks)

_______________________________________________________________ Explanation: ________________________________________________________________ ________________________________________________________________ ________________________________________________________________

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21 Question 6 (16 marks) The molecular formulae below all represent hydrocarbons: . CH4 C5H12 C3H4 C6H12 C3H6 C5H10 C25H52

C6 H6

a) Which of these hydrocarbons belong to the same homologous series as ethane? Expl...