HSC Chemistry Semester 1 Examination 2009

Marist College Kogarah

Chemistry Year 12, 2009

Semester One Examination

Name:______________________________

Teacher:JWO

Date:Tuesday, 17 March 2009

Total Time Allowed:2 hours (plus 5 minutes reading time)

Weighting:15%

Total Marks:____ / 70

Instructions

Reading time 5 minutes

Working time 2 hours

Attempt all questions.

Board approved calculators may be used.

Write using blue or black pen.

Draw diagrams using pencil.

This paper must not be removed from the Examination Room.

Exam Structure

Part A (15 Marks)/ 15 Attempt Questions 1 15 Allow about 25 minutes for this Part Mark your answers on the answersheet provided.

Part B (50 Marks)/ 55 Attempt Questions 16 25 Allow about 1 hour and 35 minutes for this Part Mark your answers in the space provided.

Total Marks: ____ / 70

Students are reminded that this is a Year 12 Examination only and cannot in any wayguarantee the content or format of the 2009 Chemistry Higher School Certificate Examination.

Part A 15 marksAttempt Questions 1-15Allow about 30 minutes for this part

Use the multiple-choice answer sheet.

Select the alternative A,B,C or D that best answers the question. Fill in the response oval completely.

Sample:2 + 4 =(A) 2(B) 6(C) 8(D) 9

A B C D

If you think you have made a mistake, put a cross through the incorrect answer and fill in the new answer.

A B C D

If you change your mind and have crossed out what you consider to be the correct answer, then indicate the correct answer by writing the word correct and drawing an arrow as follows.

A B C D

correct

Part ATotal marks (15)

Attempt Questions 1-15 Allow about 25 minutes for this part

Use the multiple choice answer sheet providedSelect the alternative A, B, C or D that best answers the question and indicate your choice with a cross (X) in the appropriate space on the grid below

1. Why does cellulose have the potential to be a raw material for building petrochemicals?

(A) It is a renewable carbon-chain polymer. (B) It has a flat, rigid structure and it is insoluble in many solvents making it useful for disposable items.(C) It is a condensation polymer composed of alternating upright and inverted /3-glucose monomers. (D) It can be decomposed by bacteria directly into ethylene, a building block of many addition polymers.

2. Which of the following substances cannot be produced in an addition reaction with ethylene?

(A) 1 ,2-dibromoethane (B) vinyl chloride (C) ethanol (D) ethane

3. Which of the following lists contains substances which are in order of increasing boiling points?

(A) ethanol, ethene, ethane (B) methanol, ethane, propanol(C) propanol, ethanol, methanol(D) methane, methanol, methanoic acid4. Which group of substances below result in a lower pH when dissolved in water?

(A)ammonia, sodium hydroxide, potassium carbonate(B)hydrogen chloride, ethanol, carbon monoxide(C)sodium oxide, magnesium oxide, calcium hydroxide(D)carbon dioxide, sulfur dioxide, hydrogen bromide

5. A student reacted sodium carbonate with excess hydrochloric acid. The balanced equation is shown below.

Na2CO3 + 2HCl 2NaCl + H2O + CO2

The student collects 1.52 L of gas from the reaction at 25oC and 100 kPa.

What was the mass of sodium carbonate that reacted?

(A)6.50 g(B)7.10 g(C)13.0 g(D)15.6 g

6. Which of the following correctly identifies the amphiprotic species with both its conjugate acid and its conjugate base?

Conjugate acidAmphiprotic speciesConjugate base

(A)HCO3-H2CO3CO32-

(B)NH4+NH3NH2-

(C)OH-H2OH3O+

(D)H2SO4SO42-HSO4-

7. A student reacts equal amounts of 5 mol L-1 sodium hydroxide solution, NaOH(aq) and of 5 mol L-1 hydrochloric acid solution, HCl(aq)at room temperature. Which is the column graph that correctly compares the temperature of the solutions before they were reacted and once the reaction is completed?

8. The accepted value for the molar heat of combustion of ethanol is 1364 kJ/mol. A 1.08 g sample of ethanol is burnt to heat a 300 mL sample of water. 75% of the heat released is absorbed by the water.

What would be the expected change of temperature of the water?

(A)0.9oC(B)6.4 oC(C)19.1 oC(D)25.5 oC9. The table below shows the pH and colour ranges of some common acid-base indicators.

Indicatorlow pH colourpH rangehigh pH colour

bromothymol blueYellow6.0-7.6blue

phenolphthaleinColourless8.3-10pink

A student carries out the following procedure:

1. Add a few drops of phenolphthalein to 50mL of 0.1M NH3 solution. 2. Add 50mL of 0.1M HNO3 (aq) to the NH3 solution.3. Add a few drops of a bromothymol blue to the mixture formed from steps 1 and 2.

Which of the following is the best prediction of the colour of the mixture at the end of each step of the procedure?Step 1Step 2Step 3

Acolourless pinkyellow

Bcolourlesspinkgreen

Cpinkcolourlessyellow

Dpinkcolourlessblue

10. The concentration of a NaOH solution is 2.0 x 10-2mol L-1.What is the pH of this solution?

(A)1.30(B)2.30(C)11.70(D)12.30

11. A solution of pH 3 has the necessary changes made to it so that it is now a pH of 5.What change has been made to the concentration of H+?(A)It has become more concentrated by a factor of 2.(B)It has become more concentrated by a factor of 100.(C)It has become less concentrated by a factor of 2.(D)It has become less concentrated by a factor of 100.12. Which of the following would be the best method to obtain a standard solution of hydrochloric acid?

(A)Weigh out 3.65 g of concentrated hydrochloric acid and dissolve this in 1 L of distilled water.(B)Measure exactly 3.65 mL of concentrated acid and make it up to 1 L with distilled water.(C)Titrate any hydrochloric acid solution against a base solution whose concentration is known accurately.(D)Dissolve a known volume of hydrogen chloride in a known volume of distilled water.

13. The table below lists some physical and chemical properties of four different carbon compounds.

CompoundBoiling point (oC)Reactivity in bromine waterSolubility in Water

W-89unreactiveinsoluble

X-104reactiveinsoluble

Y78unreactivesoluble

Z138unreactiveslightly soluble

Which alternative best identifies compound W, X, Y and Z?WXYZ

(A)C2H6C2H4C2H5OHC5H11OH

(B)C2H4C2H6C5H11OHC2H5OH

(C)C5H11OH C2H5OHC2H4C2H6

(D)C5H11OHC2H4C2H5OHC2H6

14. The curves below represent acid-base titrations. Note that the solid and dashed curves overlapped each other from 25 mL on. Which titrations are represented by the solid and dashed curves?Solid curve Dashed curve

(A)strong base + strong acidweak base + strong acid

(B)strong base + strong acid strong base + weak acid

(C)strong base + weak acidweak base + weak acid

(D)weak base + strong acidstrong base + weak acid

15. Salt solutions can be acidic, neutral or basic. Which of the following salt solution is acidic?

(A)sodium ethanoate(B)potassium nitrate(C)sodium hydrogen carbonate(D)ammonium chloride

Part BAttempt questions 16 25Allow about 1 hour and 35 minutes for this part

Answer the questions in the spaces provided.Show all relevant working in questions involving calculations.

Question 16 (4 marks)Marks

(a) Briefly describe two chemical processes encountered in this course that use a catalyst.

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(b) Identify the features of the catalysts that make them useful for the process.

2

Question 17(4 marks)

Marks

(a) Name a biopolymer that is currently being manufactured and considered as an alternative to traditional polymers such as polyethylene

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(b) Identify potential uses of this biopolymer and explain how its properties make it suitable for these applications.

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Question 18 (4 marks)

The acid shown below is used in the food industry. 4

Identify the common name and IUPAC name for this acid and explain why acids such as these are used as food additives.

Question 19 (9 marks)Marks

The flow chart below represents a series of reactions (1, 2 and 3), starting with substance X in reaction 1.

ethylene + Y

X ethanol + carbon dioxide1 Z + water2

3+ butanoic acid

(a) Write balanced chemical equations to represent reactions 1 and 2 above.

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(b) Using structural formulae, write a balanced equation to represent reaction 3 above.

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(c) Outline the conditions under which ethylene is converted to HDPE.

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Question 19 continues on page 13.Question 19 (continued)Marks

(d) Assess the significance of the reaction conditions in reaction (1) in the above diagram.

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Marks Question 20(8 marks)

A student wanted to compare the heat of combustion of 1-pentanol with that of ethanol. To do this, they burned 1.55 g of 1-pentanol to heat 250.0 mL of water from 10.0oC to 38.0oC.

(a) Draw the structural formula of 1-pentanol.

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(b) Define molar heat of combustion of a compound.1

Question 20 continues on page 14.

Question 20 (continued)

(c) Using the student's data, calculate the heat of combustion of 1-pentanol.

3

(d) Identify how you would expect the student's value to compare with the experimental value for ethanol.

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(e) Identify how you would expect the student's value to compare with the literature value (eg in the SI Data Book) for 1-pentanol. Explain your answer.

2

Question 21 (6 marks)Marks

Hydrochloric acid is a strong, monoprotic acid. It is formed when hydrogen chloride gas dissolves in water.

(a) Contrast the term strong with the term concentrated when referring to acids.2

(b) Distinguish between the terms strong and concentrated using diagrams.2

(c) Hydrogen chloride gas is bubbled through water, which results in 1.26 g of the gas dissolving.

Calculate the pH of this solution if the volume of the solution produced is 2.42 L2

Question 22(3 marks)

Use Le Chateliers Principle to relate the increase in burning fossil fuels to a possible increase in the acidity of the oceans.

4

Question 23 (5 marks)Marks

A solution of vinegar was titrated against 0.22 mol L-1 NaOH to determine its concentration. The 50.00 mL sample of vinegar was diluted to 500.00 mL and 20.00 mL aliquots of the diluted solution were titrated with phenolphthalein as the indicator. The results are shown below.

RunVolume of NaOH used (mL)

Rough23.5

123.1

223.00

322.90

(a) Justify the use of the phenolphthalein as the indicator.2

(b) Calculate the concentration of the vinegar.3

Question 24 (6 marks)Marks

Sodium hydrogencarbonate, NaHCO3, is a common laboratory chemical which readily dissolves in water. The sodium hydrogencarbonate may then react with water to form a basic solution.

(a) Identify the Lowry-Bronsted definition of an acid and a base.1

(b) Demonstrate that sodium hydrogencarbonate is acting as a base in this reaction according to the Lowry-Bronsted theory.1

(c) Justify the success of the Lowry-Bronsted theory of acids and bases over earlier ideas. Refer to the above reaction in your answer.4

Question 25 (5 marks)Marks

The following article, sourced from the internet, outlines possible future directions in ethanol production.

Cellulosic ethanol has great appeal as an alternative fuel.Cellulosic ethanol is the term given to ethanol that is derived from the cellulose content of biomass (newspaper pulp, switchgrass, etc.). It is identical to ethanol produced from sugars in corn or sugar cane.Switchgrass could be the key to future large-scale ethanol production due to its high cellulose content, its fast-growing nature and its limited need for water or fertiliser. It also thrives in places unsuitable for most crops.The major components of biomass are cellulose, starch and lignin. It is possible for cellulose and starch to be broken down into their glucose monomers and these simple sugars can then be converted into ethanol via fermentation.The remaining lignin waste could be used as a fuel. Recent developments in the industry involve burning the lignin as a heat source for processes involved in ethanol production.Ethanol then has the potential to release nearly 80% more energy than is consumed during its production. Such clever use of the bulk of the biomass material means CO2 emissions are virtually neutral in this process reducing greenhouse gas emissions by up to 85% compared to petrol.Unfortunately, cellulose requires a greater amount of processing involving costly enzymes which leads to high production costs.

Assess the potential of cellulosic ethanol as an alternative fuel

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