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2018 Senior External Examination

ChemistryPaper One — Question and response book

Friday 26 October 20189 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 — Multiple-choice response sheet

Equipment allowed• QCAA-approved equipment

• non-programmable calculator

DirectionsDo not write 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

AssessmentPaper One assesses the following assessment criteria:

• Knowledge of the subject matter

• Scientific processes

Assessment standards are at the end of this book.

After the examination sessionThe supervisor will collect this book when you leave.

Planning space

1

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 70 marks.Suggested time allocation: 1 hour 50 minutes.

Section 1 — Multiple choiceSection 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 1How many protons, neutrons and electrons does a 1939K+ ion have?

A 19 protons, 39 neutrons, 39 electrons

B 19 protons, 20 neutrons, 18 electrons

C 19 protons, 20 neutrons, 20 electrons

D 19 protons, 39 neutrons, 18 electrons

Question 2Which of the following samples of gas (under the same conditions of temperature and pressure) would have the greatest volume?A 1 g of chlorine, Cl2

B 1 g of ethane, C2H6

C 1 g of sulfur dioxide, SO2

D 1 g of carbon monoxide, CO

Question 3Molecules of the compounds carbon disulfide, carbon tetrachloride, phosphorus pentafluoride and hydrogen chloride can be represented by the following diagrams respectively:

Which of the above compounds have polar molecules?A Hydrogen chloride and phosphorus pentafluorideB All of the above except carbon disulfideC All of the molecules are polar.D Hydrogen chloride only

Part A — Knowledge of subject matter

2

Question 4The dissolving of sodium thiosulfate crystals in water may be represented by the equation

2 12 2 3 2 3Na S O (s) 2Na (aq) S O (aq) H 7.15 kJ mol+ − −→ + ∆ = +

When 0.20 mole of sodium thiosulfate dissolves in 100 mL of water in a well-insulated container, the approximate temperature change of the solution isA a fall of 7 °C.B a rise of 7 °C.C a fall of 3.5 °C.D a rise of 3.5.°C.

Question 5Which of the following molecules is a structural isomer of butanoic acid?

Question 6The following electrochemical cell was set up.

wireiron

iron(II) sulfatesolution

coppersalt bridge

copper(II) sulfatesolution

Which of the following statements about this cell is true?A The electrons will move through the salt bridge from the copper electrode to the iron electrode.

B Ions will move through the wire from the iron electrode to the copper electrode.

C The iron electrode is the cathode and the copper electrode is the anode.

D The copper electrode will gain mass.

A

C

B

D

2 12 2 3 2 3Na S O (s) 2Na (aq) S O (aq) H 7.15 kJ mol+ − −→ + ∆ = +

3

Question 7Question 7 refers to the diagram of the periodic table of the elements shown below. The letters in the diagram are not the normal symbols of the elements involved.

An element which has a half-full s subshell in its ground state electron configuration isA T

B Q

C J

D X

Question 8A sample of gas is held in a closed container at a temperature of 5 °C. What final temperature would be required in order for the average kinetic energy of the particles to be doubled?

A 10 °C

B 120 °C

C 283 °C

D 293 °C

Question 9A sample of orange juice has pH of 3.0 and a sample of tomato juice has a pH of 4.0. Compared to the [H+] of orange juice, the [H+] of tomato juice is:

A 1.0 times lower.

B 1.0 times higher.

C 10.0 times lower.

D 10.0 times higher.

Section 1 continues over next page ▬►

4

Question 10Consider the following gaseous reaction: 2 2 3A 3B A B+

Quantities of all three chemicals are placed in a 5.0 L vessel at 1 000 K and the system is allowed to come to equilibrium. The graph below indicates the changes in concentration with time.

The equilibrium constant for the reaction at 1 000 K is:

A 0.5

0.1 3(0.5)× C

0 5

0 1 0 23

.

. ( . )×

B 0.1 3(0.2)

0.5×

D

0 1 0 2

0 5

3. ( . )

.

×

End of Section 1

5

Section 2 — Short responseSection 2 has eight questions worth 60 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 structurea. Complete the table below by writing the name or formula of each substance.

Name Formula

aluminium hydroxide

Cl2O8

(1 mark)

b. Write the electron configuration for an atom of phosphorous in its ground state.

(1 mark)

c. Tick true (T) or false (F) for each of the following statements

i.

ii.

(1 mark)

d. Refer to the diagram of the periodic table of the elements shown below. The letters in the diagram are not the normal symbols of the elements involved.

Select ‘a letter’ for each of the following statements:

i.

ii.

(2 marks)

Question 11 continues over next page ▬►

T F

All isotopes of the same element have the same number of neutrons.

The number of electrons around the nucleus of a neutral atom is the same as the atomic number.

an element likely to exist as a lattice structure held together by the metallic bonds

an element likely to form a compound with hydrogen which exhibits hydrogen bonding

6

e. Sodium and chlorine are two elements in the third period of the periodic table.

i. Use your knowledge of bonding to explain why sodium is a solid but chlorine is a gas at room temperature conditions.

(2 marks)

ii. Use your knowledge of ionisation energy and electronegativity to explain why the bonds formed in the reaction between sodium and chlorine are ionic rather than covalent.

(2 marks)

Question 12 — Reacting quantities and chemical analysisa. Avogadroʼs number is 6.02 ×1023. Explain what this represents.

(1 mark)

b. Calculate the mass of strontium chloride (SrCl2) required to make 100.0 mL of 2

21.0 10 M SrCl−×solution.

(2 marks)

7

c. Write a balanced equation to represent the reaction between ethane gas (C2H6) and oxygen gas (O2) to form carbon dioxide (CO2) and water (H2O).

(2 marks)

d. When a few drops of iron(III) chloride (FeCl3) solution are added to a few drops of sodium hydroxide (NaOH) solution a precipitate is formed. When a solution of sodium nitrate (NaNO3) is added to the iron(III) chloride solution, no precipitate is formed.

On the basis of this information, write the net ionic equation for the formation of the precipitate.

(1 mark)

e. The reaction between magnesium (Mg) and dilute hydrochloric acid (HCl) is represented by the following unbalanced equation:

2 2Mg(s) HCl(aq) MgCl (aq) H (g)+ ® +

Calculate the mass of H2(g) produced when 10 g of Mg(s) is added to 250 mL of 0.1 M HCl.

(3 marks)

8

Question 13 — Oxidation and reductiona. Identify the oxidising agent (oxidant) in the chemical reaction represented by the following equation:

23 2 2Cu(s) 2NO (aq) 4H (aq) Cu (aq) 2NO (g) 2H O(l)− + ++ + → + +

Justify your selection.

(2 marks)

b. Use the table of standard reduction potentials in your resource book to decide if a spontaneous reaction would occur if a piece of solid copper (Cu) was placed in an aqueous solution of lead(II) nitrate (Pb(NO3)2). Explain your decision.

(2 marks)

c. What mass of copper would be formed on a cathode of an electrolytic cell used to obtain pure copper if a 1.5 ampere current is run through the cell for eight hours?

(2 marks)

9

Question 14 — Organic chemistrya. Complete the table below by drawing the functional group applicable to each organic class.

Class Functional group

Alkenes

Ketones

(1 mark)

b. Name the type of biological molecule that has the following structure:

(1 mark)

c. State the IUPAC name for the following substance:

(2 marks)

Question 14 continues over next page ▬►

10

d. In order to identify a compound, an organic chemist performed a series of qualitative and quantitative experiments to obtain the following data:i. molecular formula of C3H8O2

ii. properties:• soluble in water

• decolourised acidified potassium permanganate

• neutral to litmus

• does not decolourise bromine water

Use the chemistʼs data to identify the compound by giving its structural formula. All chemical reasoning should be given.

(3 marks)

11

Question 15 — Chemical periodicitya. The following diagrams represent graphs of first ionisation energies of different series of elements

against their atomic numbers.

Which diagram applies to a series of elements that starts with a noble gas and is consecutive in atomic number?

(1 mark)

b. Sodium (Na) and caesium (Cs) are both elements in Group 1 of the periodic table. Explain which element is the more reactive in terms of electron configuration.

(2 marks)

c. Hydrogen presents problems in its placement in the periodic table in that it has some properties similar to the elements in Group 1 and some properties similar to the elements in Group 17.

Beside each of the properties of hydrogen listed in the table below, record either if the stated property is typical of the elements in Group 1 or if the stated property is typical of the elements in Group 17.

Property of hydrogen Similar to group

Gas at room temperature

Forms diatomic molecules

Has one electron in its outer shell

Has one electron less than a noble gas in its outer shell

(2 marks)

12

Question 16 — Gases and the atmospherea. Describe the physical property of diffusion which is common to all gases.

(1 mark)

b. Recall Dalton’s Law of Partial Pressures.

(1 mark)

c. In the space provided sketch a curve to represent the relationship between gas pressure and volume of a fixed mass of gas at constant temperature.

(1 mark)

d. Calculate the pressure in atmospheres when 0.8 moles of a gas is placed in a 15.0 L container at a temperature of 25 °C.

(2 marks)

Volume

Pres

sure

13

Question 17 — Energy and rates of chemical reactionsa. Define bond energy and relate it to the enthalphy change in a chemical reaction.

(2 marks)

b. Sketch a potential energy–reaction coordinate diagram that could represent the mechanism for the following reaction: The overall reaction [A 2B D]+ → is exothermic.

The steps in the reaction are:A B C+ → (slow, endothermic)

C B D+ → (fast)

Label the diagram by including:

• activation energies

• activated complexes

• reaction intermediate

• ∆H

(3 marks)Reaction coordinate

Pote

ntia

l ene

rgy

Question 17 continues over next page ▬►

14

c. Cane sugar or sucrose (C12H22O11) is a significant part of our daily food intake because it is an additive in many foods. Sucrose can serve as a source of energy for the body.

Heat of formation H2O(1) : 1f 286 kJ mol−∆ = −H

Heat of formation CO2(g) : 1f 394 kJ molH −∆ = −

Heat of formation C12H22O11(s) : 1f 2226 kJ molH −∆ = −

Given the data above, calculate the energy theoretically available to the body when one mole of sucrose is oxidised to carbon dioxide and water.

(2 marks)

Question 18 — Chemical equilibriuma. Describe the meaning of the following terms:

i. strong electrolyte

(1 mark)

ii. concentrated solution

(1 mark)

iii. Lowry–Brønsted base.

(1 mark)

15

Question 18 continues over next page ▬►

b. The dichromate–chromate equilibrium can be described by the following equation:

2 22 7 2 4Cr O (aq) H O(l) 2CrO (aq) 2H (aq)- - ++ +

orange yellow

Apply Le Chatelier’s principle to explain the effect of adding aqueous sodium hydroxide (NaOH) to the solution.

(1 mark)

c. Calculate the Ka of the weak monoprotic acid HA if a 0.6 M solution has a pH of 6.

(2 marks)

d. Calculate the solubility product of calcium hydroxide (Ca(OH)2) if a saturated solution is found to have a pH of 12.

(3 marks)

16

e. Phosgene is prepared according to the reaction CO g Cl g COCl g( ) ( ) ( )+2 2

.

At a certain temperature, equilibrium is established in a 500 mL flask with a mixture which, on analysis, contained 1.5 mol of phosgene, 0.15 mol of carbon monoxide and 1.0 mol of chlorine.

In another 500 mL flask, at the same temperature and pressure, 0.20 mol of chlorine and 0.10 mol of carbon monoxide remained at equilibrium. How many moles of phosgene were produced in the second flask?

(3 marks)

End of Section 2End of Part A

17

Part B assess 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.

Suggested time allocation: 40 minutes.

Question 1 — Energy and rates of chemical reactionsIn an experiment to find the heat of combustion of ethanol (C2H5OH), a student determined the amount of heat produced when ethanol was burned to warm a known volume of water. The figure below shows the apparatus used.

a. The quantity of heat required to raise the temperature of 1 g of water by 1 °C is 4.2 J. The mass of 1 mL of water is 1 g. Use this information and the data above to calculate the amount of heat required to raise the temperature of the water in the calorimeter from 16 °C to 26 °C.

b. Using the information generated in Question 1a, calculate the heat of combustion per mole of ethanol. Molar mass of ethanol = 46 g/mol.

Part B — Scientific processes

Question 1 continues over next page ▬►

18

c. The accurate value for the heat of combustion of ethanol is 1 368 kJ/mol. Identify two ways in which the student could have improved this experiment in order to obtain a more accurate value for the molar heat of combustion of ethanol.

Question 2 — Gases and the atmosphereThe rate (R) at which gas escapes through a small hole in a container is found to be dependent on the molar mass (M) of the gas. A typical set of results (at constant temperature) is shown in the following table.

Gas Escape rate (mL/s)

H2 0.71 14.1

He 0.50 10.0

CH4 0.25 5.0

N2 0.19 3.8

O2 0.18 3.5

CO2 0.15 3.0

a. Graph escape rate vs 1

Musing the graph paper below.

19

b. Describe the relationship between escape rate (R) and molar mass (M).

c. Use your graph to predict the escape rate for neon (Ne) gas. The molar mass of neon = 20 g/mol.

Question 3 — Chemical equilibriumCarbon monoxide can react with fluorine to produce carbon oxyfluoride as shown in the equation: CO g F g COF g( ) ( ) ( )+

2 2

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.

a. Identify what gases were present in the reaction vessel at the start of the experiment and state their concentration.

b. When equilibrium for a reaction is established, no more changes in the concentrations of reactants or products occur. Mark on the graph the time when the reaction first reached equilibrium.

Question 3 continues over next page ▬►

20

c. At t = 15 minutes, a change was made to the system by the scientist. Deduce from the graph what change was made.

d. At t = 30 minutes, the temperature of the reaction vessel was decreased. With reference to the graph and using information extracted from the graph, explain if the reaction is exothermic or endothermic.

Question 4 — Materials: Properties, bonding and structureUsing information from the table below and the resource book, identify substances A, B, C, D and E from the following list and provide reasons:

• Aluminium (Al)

• Calcium carbonate (CaCO3)

• Copper (Cu)

• Copper(II) sulfate (CuSO4)

• Sodium hydroxide (NaOH)

• Mercury (Hg)

• Benzoic acid (C6H5COOH)

• Propane (C3H8)

• Sodium chloride (NaCl)

• Silicon dioxide (SiO2)

• Carbon dioxide (CO2)

MP (°C)

BP (°C)

Electro-conductivity

in solid state

Electro-conductivity in aqueous

solution

Soluble in H2O

at 20 °C

Reaction with blue

litmus

Reaction with dilute strong acid

Colour at 25 °C

A 318 1388 No Yes Yes Blue Reacts to release heat White

B 1084 2562 Yes Insoluble No No change

No reaction Brown

C 1713 2950 No Insoluble No No change

No reaction White

D –188 –42 No Insoluble No No change

No reaction

Colour-less

E 122 250 No Yes Slight Pink No reaction

Colour-less

21

Substance Name of material Reason

A

B

C

D

E

22

Question 5 — Reacting quantities and chemical analysisDesign a scientific investigation related to the generation, collection and testing of one of the following gases:

• oxygen (O2)

• hydrogen (H2)

• carbon dioxide (CO2)

a. Formulate a hypothesis for the investigation.

b. List the apparatus required.

c. In point form, describe the method employed.

23

d. Identify one safety issue.

e. What collected data would support the hypothesis you formulated in part a?

End of Part BEnd of Paper One

24

Additional response page

25

Additional response page

26

Spare graph paper

27

Spare graph paper

28 31

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© The State of Queensland (Queensland Curriculum and Assessment Authority) 2018

Copyright enquiries should be made to:

ManagerPublishing UnitEmail: publishing@qcaa@qld.edu.au

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