2013 Senior External Examination Chemistry Paper One ...€¦ · 2013 Senior External Examination...

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)

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.

Supervisor use only

QSA use only

Supervisor’s initials

Marker number

––

Candidate use

Print your candidate number here

Attach barcode here

Number of books used

1 3

Planning space

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?

Question 2

Ammonium acetate has the formula CH3CO2NH4. From this it can be concluded that

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 and

B and

C and

D and

A there are twelve atoms per formula unit.

B there are six different elements in the compound.

C carbon makes up 2/12 of the mass of the compound.

D the compound is very reactive because of the presence of the seven H atoms.

A ions in a three dimensional lattice.

B atoms held together by covalent bonds.

C molecules in a three dimensional lattice.

D molecules held together by hydrogen bonds.

Z8436 Z

8430

Z5426 Z

5626

Z105 Z

2010

Z11 Z

12

2013 Chemistry — Paper One — Question and response book 1

Question 4

1.0 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

Question 5

Fluorine reacts spontaneously with bromide ions according to the following equation:

Which of the following is the strongest oxidising agent?

Question 6

Which of the following molecules is a structural isomer of propanoic acid?

A 1.0 g.

B 8.0 g.

C 9.0 g.

D 11.0 g.

A F2(g)

B Br–(aq)

C F–(aq)

D Br2(g)

A

B

C

D

F2 g 2Br aq 2F aq Br2 g ++ – –

H C C C C OH

OH H H

H H H

HO C C C OH

OH H

H H

O C C C O

H H H

H

HO C C C OH

H

H H H

2 2013 Chemistry — Paper One — Question and response book

Question 7

A section of the periodic table has had the chemical symbols replaced by letters.

The element which belongs to the d block of the periodic table is

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?

Question 9

An accurate description of a 6M solution of CH3COOH (acetic acid) of Ka = 1.8 x 10–5 would be a

A K.

B L.

C M.

D N.

A 20 °C

B 120 °C

C 283 °C

D 293 °C

A dilute weakly acidic solution.

B dilute strongly acidic solution.

C concentrated weakly acidic solution.

D concentrated strongly acidic solution.

N

K

L

M


Question 10

During the progress of a chemical reaction,

End of Section 1

A most collisions involve only two particles.

B a successful collision is one in which the reactants are formed again.

C the activated complex has a lower energy than either reactants or products.

D the rate can be determined by an inspection of the relevant chemical equation.


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?

.....................................................................................................

(½ mark)

ii. What is the mass number?

.....................................................................................................

(½ mark)

b. List the type of attractive force that is overcome when each of the following substances melt.

(2 marks)

c. Give the formula for the sulfate ion.

.................................................................

(½ mark)

d. Name the substance represented by the formula Mg(OH)2.

.................................................................

(1 mark)

Substance Force

Copper

Copper sulfate

Ice

Diamond


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?

(3 marks)

f. Draw Lewis diagrams for the following molecules and give the shape of each molecule..

(2 marks)

Pure water/Solution of sodium chloride in water

Test:

Results:

Iron sulfide/Mixture of iron and sulfur

Test:

Results:

Molecule Lewis diagram Shape of molecule

CH4

NCl3


Question 12 — Reacting quantities and chemical analysis

a. Define the following terms:

i. Avogadro’s number

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(1 mark)

ii. relative atomic mass

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(1 mark)

b. Balance the following equation..

(2 marks)

c. Calculate:

i. the mass, in grams, of one molecule of H2S.

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.....................................................................................................

(1 mark)

ii. the number of hydrogen atoms in five molecules of CH3COOH.

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(1 mark)

iii. the concentration (molarity) of the nitrate ions in an aqueous solution which contains45.0 g of dissolved aluminium nitrate in a volume of 800.0 mL.

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(2½ marks)

HCl(aq) + Fe2O3(s) FeCl3(s) + H2O(l)


d. Octane 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?

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(2½ marks)

C8H18 g


Question 13 — Oxidation and reduction

a. Explain the meaning of the following terms:

i. electrolytic cell

.....................................................................................................

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(1 mark)

ii. oxidising agent (oxidant)

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.....................................................................................................

(1 mark)

b. Does the following equation represent an oxidation–reduction reaction? Explain your reasoning.

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(1 mark)

c. Will a reaction occur spontaneously when a piece of solid copper is placed in a 1.0M Pb2+(aq) solution? Explain your reasoning.

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(2 marks)

2Al s Fe2O s 3+ Al2O s 3 2Fe s +


d. An electrochemical cell is constructed using:

• two beakers

• 1.0M solutions of Fe2+ and Pb2+

• clean pieces of Fe and Pb

• a piece of porous paper which had been soaked in a KNO3 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)


Question 14 — Organic chemistry

a. Complete the following table..

(2 marks)

b. Draw the structure of methyl butanoate.

(1 mark)

c. Name the organic substance with the following structure.

(1 mark)

d. What would be the product/s of the following chemical changes?

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)

General formulaStructure which contains

three carbon atoms

alkenes

ketones

i.

(1 mark)

ii.

(1 mark)

C

CH3

CH2

CH3

CH3

CH2

H C3

CH2

CH2 CH2

CH2

............................................................

CH4 g Br2 1 +uv radiation

............................................

C2H5OH 1 MnO4–

aq H+

aq + +............................................



Question 15 — Chemical periodicity

a. State the trends in the periodic table for the following:

i. first ionisation energy of the group 2 elements

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(½ mark)

ii. atomic radius of the period 3 elements

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(½ mark)

b. Write the electron configuration for an aluminium atom.

.....................................................................................

(1 mark)

c. The first six ionisation energies of the nitrogen atom, in kJ mol–1, are listed in the following table.

Explain why:

i. E6 is much greater than E5

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......................................................................................................

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(1 mark)

ii. the first ionisation energy (E1) for C (1086 kJ mol–1) is less than E1 for N (1400 kJ mol–1).

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......................................................................................................

......................................................................................................

.....................................................................................................

(1 mark)

E1 1400

E2 2850

E3 4560

E4 7450

E5 9460

E6 53 100

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

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ii. bromine is less reactive than fluorine.

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(2 marks)


Question 16 — Gases and the atmosphere

a. Describe a factor which affects the concentration of ozone in the upper atmosphere.

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(1 mark)

b. List one major gas in the earth’s atmosphere and describe how it affects human welfare.

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(1 mark)

c. What is the normal boiling point of a substance whose vapour pressure varies as shown in the graph below?

..........................................................................................................

(1 mark)

050 60 70 80 90 100

Temp ( C)°

Vapour pressure(kPa)

25

50

75

100

125

150

175

200


d. Consider the two bulbs below.

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?

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(3 marks)

He Ne

1.5 atm1 L

pressure =volume =

1.0 atm2 L

pressure =volume =

Bulb A

negligiblevolume inthe valve

Bulb B


Question 17 — Energy and rates of chemical reactions

a. Define the following terms:

i. catalyst

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(1 mark)

ii. activated complex

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(1 mark)

b. State the basic postulates of the collision theory of reactions.

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(2 marks)

c. Given the following data,

calculate for the reaction below.

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(2 marks)

S s 112---O2 g SO3 g + H 395.2 kJ–=

2SO2 g O2 g 2SO3 g + H 198.2 kJ–=

H

S s O g 2 SO g 2+


d. The following energy diagram shows the energy change in kJ mol–1associated with the use of glucose (C6H12O6) in body processes.

i. Is the reaction exothermic or endothermic? Explain why.

.....................................................................................................

.....................................................................................................

(1 mark)

ii. Calculate the energy change per gram of glucose.

.....................................................................................................

.....................................................................................................

.....................................................................................................

(1 mark)

Energy(kJ mol )–1

reactants

180 kJ mol–1

Reaction coordinate

products

300 kJ mol–1


Question 18 — Chemical equilibrium

a. Define pH.

..........................................................................................................

..........................................................................................................

(1 mark)

b. Complete the following table.

(1½ marks)

c. A dynamic equilibrium is:

i. recognised by

......................................................................................................

......................................................................................................

ii. explained by

......................................................................................................

......................................................................................................

(1 mark)

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.

(red) (blue)

i. Write the equilibrium law expression.

(1 mark)

ii. Explain why the mixture becomes more blue when it is warmed.

......................................................................................................

......................................................................................................

......................................................................................................

(1 mark)

Term Description Example

Weak electrolyte

Co H O2 62 +

aq 4Cl00–

aq + CoCl42 –

aq 6H2O 1 +


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.

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(4 marks)

f. 10.0 mL of 0.25M Mg(NO3)2 solution is mixed with 25.0 mL of 0.20M NaF solution.

Will a precipitate form?

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(4 marks)

End of Section 2

End of Part A

Kspfor MgF2 8 108–=


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.

Determine the group of the periodic table to which each element belongs. You must justify your choices.

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Elements Properties

A • reacts vigorously with water to liberate a gas which ignites and burns

B • is very unreactive

• is a monatomic gas sometimes used in light bulbs

C • 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 DC2

• 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 EO2 (O = oxygen)


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 J2+, L2+, M2+ and N2+ 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 J2+ and L2+ only

• metal N was coated with another substance when placed in solutions of J2+, L2+ and M2+.

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.

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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 (C2H4O2) 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.

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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.

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.

..........................................................................................................

..........................................................................................................

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 changeproduces a black solid

no change

Melting point °C 842 –101 1085 1200

Combine with acid

generates a large amount of heat

slight colour change

generates heat, colour change

no reaction

Periodic table group

2 17 unknown unknown

Electrical conductivity

good non-conductor good good

Tensile strength high nil moderate high


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 (C6H14) of actual heat value (4160 kJ mol–1) was first used in the burner. Pentane (C5H12) was then substituted for the hexane and all other conditions kept constant.

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.

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...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

...............................................................................................................

Burning hexane

Initial water temperature (°C)

Final water temperature (°C)

Mass of hexane burned (g)

20.0 70.0 0.50

Burning pentane

Initial water temperature (°C)

Final water temperature (°C)

Mass of pentane burned (g)

19.0 68.0 0.43

thermometer

beaker

flame

cloth wick

fuel

glass bulb

clamp

100 ml of H2O


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End of Part B

End of Paper One


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2013 Senior External Examination Chemistry Paper One ...€¦ · 2013 Senior External Examination...

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