PLACE LABEL HERE · Chemistry – Part 1 Page 8 For Marker Use Only Question 8 This question assesses Criterion 4. (a) A strip of zinc metal and a strip of tin metal can be experimentally

Pages: 12 Questions: 8 ©Copyright for part(s) of this examination may be held by individuals and/or organisations other than the Tasmanian Qualifications Authority.

PLACE LABEL HERE

Tasmanian Certificate of Education

CHEMISTRY

Senior Secondary

Subject Code: CHM5C

External Assessment

2008

Part 1

Time: approximately 45 minutes

On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the syllabus statement: Criterion 4 Develop and evaluate experiments. Criterion 7 Demonstrate an understanding of the fundamental principles and

theories of electrochemistry. Criterion Mark

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Chemistry – Part 1

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CANDIDATE INSTRUCTIONS Candidates MUST ensure that they have addressed ALL of the externally assessed criteria on this examination paper. Answer ALL questions (making sure you answer all parts within each question so that the criteria can be assessed). Answers must be written in the spaces provided on the examination paper. The 2008 Chemistry Information Sheet can be used throughout the examination. No other printed material is allowed into the examination. TQA approved graphics calculators can be used throughout the examination. Each booklet is of equal value (40 marks). This examination is 3 hours in length; it is recommended that you spend no more than 45 minutes on any one of the FOUR parts to this examination. In calculations no credit can be given for incorrect answers unless they are accompanied by details of the working. Some credit will be given for unsimplified answers. Appropriate units must be included.

NOTE: 1 litre (L) = 1000 millilitres (mL) = 1 dm3 = 1000 cm3. The last question in each part is used in the assessment of Criterion 4. All written responses must be in English.


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Question 1 This question assesses Criterion 7. (a) List the oxidation states of bromine in the following compounds: (2 marks)

!

Br2O .................................................

!

BrO2 .......................................................... HBr ...................................................

!

Br2 ............................................................. (b) Is the following equation an example of oxidation-reduction? Give reasons. (2 marks)

!

SF4(g) + H2O(g) " SOF2(g) + 2HF(g) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... Question 2 This question assesses Criterion 7. In acidic solution the perchlorate ion,

!

ClO4", will oxidise the sulfite ion,

!

SO32" , to sulfate,

!

SO42" , and is reduced to chlorine gas,

!

Cl2 . Write the two half equations, and hence the overall equation for this reaction. (4 marks) ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................


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Question 3 This question assesses Criterion 7. Gold is readily found in its natural state (i.e. metallic gold), whereas zinc is only found combined with other elements in ores such as zinc sulfide. Explain this difference in terms of E0 values of the two metals and common oxidisers found in nature. (4 marks) ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ Question 4 This question assesses Criterion 7. Dorothy has several mercury amalgam fillings and experiences a tingling sensation in her mouth when she bites on aluminium foil. Explain this in terms of electrochemistry, assuming that the mercury amalgam is acting as an inert electrode. Include all relevant half equations. (4 marks) ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................


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Question 5 This question assesses Criterion 7. Shane and Heather, two students in a Chemistry class, were given a standard chromium half cell and asked to form a cell with a theoretical maximum net E˚ of 1.51 volts (under standard conditions). (a) Name a suitable half-cell they could have chosen. (1 mark) ....................................................................................................................................... (b) Give the shorthand representation for the cell formed. (1 mark) ....................................................................................................................................... (c) On the diagram below label the electrodes, the solutions, the anode and anode reaction,

the cathode and cathode reaction, the salt bridge and show the direction of electron flow in the external circuit and ion flow through the salt bridge for the cell they made.

(5 marks)

Reaction: Reaction: (d) The cell was accidentally left on over the weekend. How would you expect the cell to

be performing on Monday compared to Friday? Explain your reasoning for the expected performance. (3 marks)

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


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Question 6 This question assesses Criterion 7. A platinum catalyst has become ‘poisoned’ with a deposit of tin. In an attempt to regenerate the platinum the tin is converted to

!

Sn4+ by electrolysis.

What mass of tin would be removed after 5.00 hours, if the effective current was 0.200 mA? (4 marks) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... Question 7 This question assesses Criterion 7 A statue made from iron and coated with a thin layer of gold was scratched. Will the exposed iron rust? Explain. (2 marks) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................

Gold layer

Iron


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Question 8 This question assesses Criterion 4. (a) A strip of zinc metal and a strip of tin metal can be experimentally distinguished using a

!

Fe/Fe2+ half cell and appropriate apparatus and meters.

On the diagrams of the apparatus below, label the positive and negative electrodes, the metal and metal ion in each half cell, the half reaction expected and the maximum reading on the voltmeter. (3 marks)

Reaction: Reaction:

Reaction: Reaction:

Question 8 continues opposite.

V

V


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Question 8 (continued) (b) Acidified nitrate ion,

!

NO3"(aq) , and bromide ion,

!

Br"(aq) , are predicted not to react at

1.00 mol

!

L"1 and 25˚C using the standard reduction potentials.

Some reports suggest that deviation from standard conditions leads to a reaction. Design an experiment to test whether these reports are true. Include the experimental

procedure, the variables you would need to keep constant and the expected results. (5 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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PLACE LABEL HERE


CHEMISTRY

Senior Secondary

Subject Code: CHM5C

External Assessment

2008

Part 2


On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the syllabus statement: Criterion 4 Develop and evaluate experiments. Criterion 8 Demonstrate knowledge and understanding of the principles and

theories of thermochemistry, kinetics and equilibrium. Criterion Mark

8 /32

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Question 9 This question assesses Criterion 8. (a) Oxalic acid, written

!

H2C2O4(aq) or

!

(COOH)2(aq) is a weak acid in aqueous solution. The first stage of the ionization is:

!

H2C2O4(aq) + H2O(l)

!

HC2O4"

(aq) + H3O+

(aq) Write an expression for

!

Ka. (1 mark) (b) Oxalic acid and ethanol react as follows: (Note: all substances are soluble in ethanol.)

!

(COOH)2 + 2C2H5OH

!

(COOC2H5)2 + 2H2O

Write the expression for the equilibrium constant. (1 mark) (c) Explain how water is acting differently in each equation and the effect of this in the

equilibrium constant expressions in (a) and (b). (2 marks) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................


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Question 10 This question assesses Criterion 8. Consider the following equilibrium reaction between hydrogen and benzene producing cyclohexane:

!

3H2(g) + (a) Use Le Chatelier’s Principle or the Equilibrium Law to explain two separate methods

that would maximize the yield of cyclohexane. (4 marks) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... (b) Platinum is used as a catalyst for this reaction. Explain the effect of the catalyst on the

equilibrium reactions and the equilibrium position, indicating clearly the benefit of adding the catalyst. (2 marks)

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

(g) (g)

CH2

CH2 CH2

CH2 CH2

CH2


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Question 11 This question assesses Criterion 8. Solid calcium oxalate exists as the monohydrate,

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CaC2O4"H2O, and has very low solubility in water.

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CaC2O4"H2O(s)

!

Ca2+(aq) + C2O4

2"(aq)

!

Ksp = 2.11"10#9

Calculate the maximum concentration of oxalate ion that will dissolve in a solution of 0.100 mol

!

L"1 calcium nitrate.

(2 marks) ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................ ................................................................................................................................................


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Question 12 This question assesses Criterion 8. Joan and Rebecca were investigating the rate of the reaction between copper carbonate and hydrochloric acid at a temperature of 4˚C. They worked in a constant temperature room set at 4˚C and added 0.500 mole of solid crushed blue-green copper carbonate,

!

CuCO3, to 1.50 L of a 0.100 mol

!

L-1 solution of

hydrochloric acid, HCl in an open flask.

!

2HCl(aq) + CuCO3(s) " H2O(l) !+ CO2(g) + Cu2+

(aq) + 2CI-(aq)

(a) Explain why it was necessary to use an open flask. (1 mark) ....................................................................................................................................... ....................................................................................................................................... (b) Explain how and why changing the concentration of the hydrochloric acid and the

particle size of the crushed solid could affect the rate of the reaction. (3 marks) ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... (c) The next day they repeated the experiment in the school laboratory using the same

crushed copper carbonate and the same acid. They found that the rate had increased. Explain this discrepancy in terms of collision theory. (3 marks)

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



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Question 12 (continued) (d) On the graph grid below draw a sketch showing the rate of disappearance of the two

reactants and the rate of formation of the

!

Cu2+(aq) ions, marking in the scale for the

amount (mole). Label each line. (5 marks)

Space for calculations if required: ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... ....................................................................................................................................... .......................................................................................................................................

amount (mole)

Time


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Question 13 This question assesses Criterion 8. (a) What does the bond energy of a chemical bond represent? (1 mark)

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

....................................................................................................................................... (b) Some bond energies for bonds in gaseous molecules are listed below:

Bond type Bond energy (kJ mol

!

-1)

C-H 416 C=C 598 C-C 346 H-H 436

Use the bond energies in the table to calculate

!

"H for the conversion of ethane to ethene. What does the result indicate about the reaction? (2 marks)

!

CH3 - CH3(g) " CH2 = CH2(g) + H2(g)

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

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

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

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

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

....................................................................................................................................... (c) Draw a graph to show the changes of energy as this reaction proceeded on the axes

below. Show

!

"H and

!

Ea. (2 marks)

E

Reaction Coordinate


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Question 14 This question assesses Criterion 8. Calculate

!

"H for the oxidation of ammonia,

!

NH3, to nitrogen dioxide,

!

NO2 .

!

4NH3(g) +7O2(g) " 4NO2(g) + 6H2O(g) Use the following data: (3 marks)

!

N2(g) + 3H2(g)

!

"

!

2NH3(g)

!

"H = #92 kJ mol-1

!

N2(g) + 2O2(g)

!

"

!

2NO2(g)

!

"H = #68 kJ mol-1

!

2H2(g) +O2(g)

!

"

!

2H2O(g)

!

"H = #484 kJ mol-1

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


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Question 15 This question assesses Criterion 4. In some European countries common salt, solid sodium chloride, is used on roads to melt a mixture of snow and ice and water. (a) Jacqueline and Lyndon were investigating the chemistry involved in this process as a

student research project. They thought that adding some sodium chloride caused the melting because the temperature of the mixture was raised when solid sodium chloride was converted to a solution.

To check this they set up an experiment where they added 10.0 g of sodium chloride to 1.00 L of tap water at 18˚C and checked the temperature of the mixture as the sodium chloride dissolved. They could not detect any significant temperature change.

(i) Explain why this experiment did not really address the question of the sodium

chloride melting the ice on the road. (2 marks) .............................................................................................................................. .............................................................................................................................. .............................................................................................................................. .............................................................................................................................. (ii) Suggest modifications to the experiment to make it more applicable. (1 mark) .............................................................................................................................. .............................................................................................................................. (b) Claire and Paul however thought that adding some sodium chloride caused the melting

because the freezing point of the salt solution is lower than the freezing point of the pure water. Claire and Paul knew that at the freezing point/melting point an equilibrium exists between the solid and liquid states.

(i) Write an equation to represent the equilibrium. (1 mark)

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

(ii) Explain why the ice would melt if this were true. (2 marks) .............................................................................................................................. .............................................................................................................................. .............................................................................................................................. ..............................................................................................................................



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Question 15 (continued)

(iii) Outline a method they could have used to check their idea. (2 marks) ............................................................................................................................ ............................................................................................................................ ............................................................................................................................ ............................................................................................................................


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PLACE LABEL HERE


CHEMISTRY

Senior Secondary

Subject Code: CHM5C

External Assessment

2008

Part 3


On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the syllabus statement: Criterion 4 Develop and evaluate experiments. Criterion 9 Demonstrate knowledge and understanding of the properties and

reactions of organic and inorganic matter. Criterion Mark

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Question 16 This question assesses Criterion 9. (a) Explain why the element potassium has the ground state electron configuration of

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1s22s22p63s23p64s1, rather than

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1s22s22p63s23p63d1. (1 mark) ..................................................................................................................................... ..................................................................................................................................... (b) Explain how atoms of potassium can be changed to have the excited electron

configuration of

!

1s22s22p63s23p63d1. (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... Question 17 This question assesses Criterion 9. (a) Describe and explain the trend in atomic radii of the atoms Na, Mg, Al and Si. (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) Describe the trend in the atomic radii of the atoms F, Cl, and Br. Explain how this

affects their ease of conversion to the ions

!

F" ,

!

Cl" , and

!

Br". (3 marks)

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


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Question 18 This question assesses Criterion 9. (a) Explain the concept that Mendeleev used in drawing up his original version of the

Periodic Table and how he was able to predict the properties of elements that were unknown at that time. (3 marks)

..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) A gaseous element, X, has the properties of a non-metal, and forms compounds with

chlorine, sodium and hydrogen. The empirical formulae of these compounds are all in the ratio 1:3.

Identify the element, clearly indicating your reasons. (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 19 This question assesses Criterion 9. The halogens combine with hydrogen to form gases, HCl, HBr, and HI. These gases dissolve in water to form acidic solutions. (a) Explain, with the aid of an equation, why they are defined as acids when dissolved in

water. (1 mark) ..................................................................................................................................... ..................................................................................................................................... (b) Discuss the relative strength of these acids based on the strength of the bond between

hydrogen and the halogen. (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (c) The element fluorine also forms a gas with hydrogen, HF. However it is only a weak

acid in aqueous solution. Give a possible explanation for this. (1 mark) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 20 This question assesses Criterion 9. Complete the following table: (4 marks)

Name Structural formula

Functional group present:

Functional group present: Secondary alcohol Heaviest mass seen in mass spectrum = 60 amu

2,5, -dichloro-2-methylheptane

Empirical Formula:

CH3 – CH2 – O – C = O CH2 - CH3

Functional group present:

!

"CH2 "CH3

!

CH2 "CH3


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Question 21 This question assesses Criterion 9. Elemental analysis of two organic liquids indicated they were composed of carbon, hydrogen and oxygen. Mass spectral analysis showed that they both have the same molecular mass of 58. Infrared spectroscopic evidence shows that both contain one

!

C =O bond and no other oxygen atoms. (a) What is the molecular formula of the two compounds? (1 mark) ..................................................................................................................................... ..................................................................................................................................... (b) What are the structural formulae and names of the two compounds? (2 marks) Compound 1: ..................................................................................................................................... Compound 2: ..................................................................................................................................... (c) Explain how you would distinguish between the two experimentally, using acidified

potassium permanganate solution. Include relevant equations. (3 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 22 This question assesses Criterion 9. The synthetic polymer polyacrylonitrile, or orlon, is used in the clothing industry. The monomer has the structural formula:

!

CH2 = C (a) Draw the repeating unit for the addition polymer, polyacrylonitrile. (1 mark)

(b) If the average molar mass of polyacrylonitrile is 61480 g

!

mol"1, calculate the

average number of repeating units in the polymer. (1 mark) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... Question 23 This question assesses Criterion 9. The reaction of steam with alkenes is sometimes used to make alcohols. Propene was reacted with steam under suitable conditions. Write equation(s) to illustrate what product(s) could be formed, showing all structural formulae. (3 marks) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................

CN

H


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Question 24 This question assesses Criterion 4. (a) Paul and Julie were given three unlabelled bottles containing liquid organic

compounds. They were told that one was a carboxylic acid, one was a tertiary alcohol and the other a chloroalkane. They were asked to experimentally identify each using chemical tests.

What tests could they have done and what results would enable them to positively

identify each? (6 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................



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Question 24 (continued) (b) Dominic and Rebecca were investigating the acidic properties of acids of sulfur and

selenium. Explain how they could experimentally determine whether selenic acid,

!

H2SeO4 , was a stronger or weaker acid than sulfuric acid,

!

H2SO4 . (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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PLACE LABEL HERE


CHEMISTRY

Senior Secondary

Subject Code: CHM5C

External Assessment

2008

Part 4


On the basis of your performance in this examination, the examiners will provide a result on the following criteria taken from the syllabus statement: Criterion 4 Develop and evaluate experiments. Criterion 10 Apply logical processes to solve quantitative chemical problems.

Criterion Mark

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Question 25 This question assesses Criterion 10. (a) Calculate the percentage by mass of oxygen in sodium stearate,

!

C18H35O2Na . (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) The singly charged cation in a compound of an old antifouling paint contained tin,

carbon and hydrogen. Analysis showed that the cation contained 40.9% tin, 49.7% carbon and 9.4% hydrogen by mass.

Calculate the empirical formula of the cation. (3 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 26 This question assesses Criterion 10. Ores of zirconium usually contain hafnium as well. The metal that is extracted by electrolysis is also a mixture of both metals and they are extremely difficult to separate. If the mixture contains 89.00% zirconium and 11.00% hafnium, calculate the mass of 1.000 mole of this mixture. (2 marks) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. Question 27 This question assesses Criterion 10. Calculate the pH of a mixture of 150 mL of a 0.0150 mol

!

L"1 sulfuric acid solution,

!

H2SO4(aq) and 50.0 mL of a 0.0300 mol

!

L"1 potassium hydroxide solution,

!

KOH(aq) . (Assume full dissociation of the sulfuric acid.) (3 marks) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................


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Question 28 This question assesses Criterion 10. Hydrogen peroxide,

!

H2O2, oxidizes acidified iodide ion,

!

I" , according to the following

equation.

!

H2O2(aq) + 2H+

(aq) + 2I"

(aq) # 2H2O(l) + I2(aq) In an experiment the initial rate of disappearance of the

!

H2O2 was 30

!

µmol

!

L"1s"1. What

was the rate of disappearance of the

!

I"? (1 mark)

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


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Question 29 This question assesses Criterion 10. (a) Don and Denys stopped for the night during a meteorological field trip near the top of a

mountain. They released a small weather balloon of volume 710 L. The conditions at the time were –2˚C and 80.5 kPa.

Calculate what the volume of the balloon would have been at 17˚C and 101.3 kPa. (3 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) A volatile organic solvent,

!

C3H6O , becomes explosive at gaseous concentrations greater than 1195 mg

!

L"1 in air at 39.5˚C. What is the partial pressure of the vapour at

this limit? (4 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 30 This question assesses Criterion 10. Life support systems in the Russian manned ‘Soyuz’ space flights involved air purification units that absorbed carbon dioxide with sodium superoxide,

!

NaO2 , while regenerating oxygen.

!

4NaO2(s) + 2CO2(g) " 2Na2CO3(s) + 3O2(g) 100 g of sodium superoxide is reacted with 42.5 g of carbon dioxide: (a) What is the maximum mass of oxygen that can be obtained? (4 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) What mass of the reagent in excess is left over after the reaction is complete? (2 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... .....................................................................................................................................


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Question 31 This question assesses Criterion 10. The amount of oxygen in a container was determined by using it to oxidise acidified

!

Fe2+(aq) ion in the presence of a cobalt catalyst.

!

4Fe2+

(aq) + O2(g) + 4H+

(aq) " 4Fe3+

(aq) + 2H2O(l) 324 mL of a 0.200 mol

!

L"1 solution of the acidified

!

Fe2+(aq) was required to completely

react with the oxygen in the tank. (a) Calculate the mass of oxygen in the tank. (3 marks) ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... ..................................................................................................................................... (b) What is the minimum volume of 2.00 mol

!

L"1 sulfuric acid solution needed for the

reaction? (1 mark) ..................................................................................................................................... ..................................................................................................................................... (c) What volume of 12.0 mol

!

L"1 sulfuric acid would be needed to make up the solution

required in (b)? (1 mark) ..................................................................................................................................... .....................................................................................................................................


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Question 32 This question assesses Criterion 10. A gold mining company found 3 ore deposits suitable for mining. The amount (mass) of gold per tonne of ore, the percentage of gold that could be extracted from each ore with a cyanide leach method and the costs of processing each ore were determined. The cost of safe disposal of the cyanide waste was also calculated.

Ore Moles of gold per tonne of

ore (g)

% gold able to be extracted

Cost of processing per gram of gold extracted ($)

Cost of safe cyanide waste disposal per tonne of ore

($) A 0.11 90 10 130 B 0.13 80 8 192 C 0.17 70 11 98

Calculate the cost per gram of extracted gold for the ores A, B, C. Include all the associated costs. (3 marks) .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. .............................................................................................................................................. ..............................................................................................................................................


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Question 33 This question assesses Criterion 4. An acidified solution of iron(II) sulfate,

!

FeSO4(aq), that was meant to be of concentration 0.0500 mol

!

L"1, was prepared for an experiment. However the students in the class thought

that the solution was contaminated. Their teacher asked them to check this experimentally. (a) What was the most likely contaminant? Explain. (1 mark) ..................................................................................................................................... ..................................................................................................................................... (b) How would this contamination affect the actual concentration of the iron(II) sulfate

solution? (1 mark) ..................................................................................................................................... ..................................................................................................................................... (c) Michael and Peter decided to titrate the solution against a standardised potassium

permanganate solution,

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KMnO4(aq) in order to find its actual concentration.

(i) How could they identify the end point? (1 mark)

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

(ii) Explain how the titration would enable them to determine the real concentration

of the iron(II) sulfate solution. (2 marks)

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Question 33 (continued) (d) Jenny and Janet decided they would check the concentration of the iron(II) sulfate

solution by reacting it with zinc. Would this be a good choice? Explain, including the effect this would have on the result. (3 marks)

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PLACE LABEL HERE · Chemistry – Part 1 Page 8 For Marker Use Only Question 8 This question assesses Criterion 4. (a) A strip of zinc metal and a strip of tin metal can be experimentally