STAV 2009 Chemistry Exam 1

STAV

SlAV Publishing 2009

I Student name

PUBLISHING

CHEMISTRYUnit 3

Trial ExaminationQUESTION AND ANSWER BOOKTotal writing time: 1 hour 30 minutes

Structure of bookSection

A

8

Number ofquestions

20

9

Total

Number ofmarks

20

66

86

• Students are permitted to bring into the examination room: pens, pencils, high lighters, erasers,sharpeners, rulers, one scientific calculator.

• Students are NOT permitted to bring into the examination room: blank sheets of paper and/or white outliquid/tape, mobile phones and/or any other unauthorised electronic devices.

• A copy of the official VCAA Data Book (printed or photocopied) can be brought into the trial examination.

Materials supplied• Question and answer book of 17 pages, with a detachable answer sheet for multiple-choice questions inside

the front cover.

Instructions• Detach the answer sheet for multiple-choice questions during reading time.• Write your name in the space provided above on this page and on the answer sheet for multiple-choice

questions.• All written responses should be in English.

At the end of the examination• Place the answer sheet for multiple-choice questions inside the front cover of this book.• You may keep your copy of the VCAA Data Book.

Published by SlAV Publishing. SlAV House. 5 Munro Street. Coburg VIC 3058 Australia.Phone: 61 + 3 9385 3999 • Fax: 61 + 3 9386 6722 • Email: [email protected] Website: http://www.sciencevictoria.com.au/stavpublishing© SlAV Publishing April 2009ABN 61 527 110 823

All rights reserved. Except under the conditions described in the Copyright Act 1968 of Australia and subsequent amendments. no part of this publicationmay be reprinted. reproduced or utilised in any form or by any electronic. mechanical, or other means, now known or hereafter invented. includingphotocopying and recording. or in any other information storage or retrieval system, without permission in writing from the publisher.

STA V Publishing2009

CHEMISTRYUnit 3 Trial Examination

MULTIPLE CHOICE ANSWER SHEET

I STUDENTNAME:

INSTRUCTIONS: USE PENCIL ONLY• Write your name in the space provided above.• Use a PENCIL for ALL entries.• If you make a mistake, ERASE it - DO NOT cross it out.• Marks will NOT be deducted for incorrect answers.• NO MARK will be given if more than ONE answer is completed for any question.• Mark your answer by SHADING the letter of your choice.

ONE ANSWER PER LINE ONE ANSWER PER LINE

1 0 0 [I] [E] 11 0 0 [I] [E]

2 0 0 [I] [E] 12 0 0 [I] [E]

3 0 0 ~ [E] 13 0 0 [I] ~

4 0 ~ [I] [E] 14 0 0 [I] ~

5 0 0 [I] ~ 15 0 ~ ~ ~

6 0 ~ [I] [E] 16 0 ~ [I] ~

7 0 ~ [I] ~ 17 0 ~ [I] ~

8 0 ~ [I] ~ 18 0 ~ [I] ~

9 0 ~ [I] ~ 19 0 ~ [I] ~

10 0 ~ [I] ~ 20 0 ~ [I] ~

© STAV Publishing 2009


SECTION A - Multiple-choice questions

Instructions for Section A

Chemistry Unit 3 Trial Examination

Answer all questions in pencil on the answer sheet provided for multiple-choice questions.

Choose the response that is correct or that best answers the question.A correct answer scores 1, an incorrect answer scores O.Marks will not be deducted for incorrect answers.

No mark will be given if more than one answer is completed for any question.

Question 1

The IUPAC name for the compound whose structure is given below is

A. 4-chlorohex-4-ene

B. 3-chlorohex-2-ene

C. 4-chlorohex-S-ene

D. 2-chlorohex-2-ene

Question 2

The molecular formula of the amino acid, tyrosine is

Question 3

DNA has an overall negative charge because of a negative charge on the

A. deoxyribose groups

B. nitrogen bases

C. sugar groups

D. phosphate groups


Question 4

2 Chemistry Unit 3 Trial Examination

The difference in molar mass between the bases guanine and cytosine is

A. 12 g

B. 26 g

C. 28 g

D. 40 g

Question 5

A biofuel formed from methanol and stearic acid would have the molecular formula

A. CH3(CH2)16COOCHzCH3

B. HCOOCHz(CH2)16CH3

C. CH3(CHz)I6COOCH3

D. CH3COOCHlCHz)16CH3

Question 6

An antacid is known to contain 400 mg of magnesium hydroxide, Mg(OH)z (M = 58.3 g mor l), per

10.0 mL. The number of mole of hydroxide ions in 1.0 L of the antacid would be closest to

A. 1.4 X 10-3

B. 1.4 X 10-2

C. 1.4 X 10-1

D. 1.4

Question 7

The mass of MgClz that would contain 0.25 mole of chloride ions is closest to

A. 11.9 g

B. 14.9 g

C. 23.8 g

D. 95.2 g

© STAV Publishing 2009 3 Chemistry Unit 3 Trial Examination

The next three questions refer to the following information.

3.27 g of zinc metal is completely reacted in 250 mL of concentrated hydrochloric acid to give gaseoushydrogen according to the equation

Zn(s) + 2HC1(aq) ~ ZnCh(aq) + BzCg)

Question 8

The volume in htres of hydrogen gas produced at 25°C and 1.00 atm pressure is closest to

A. 0.103

B. 1.22

C. 206

D. 124

Question 9

The concentration of zinc ions in the solution after all ofthe zinc has reacted is closest to

A. 0.050 M

B. 0.100 M

C. 0.200 M

D. 0.013 M

Question 10

The reaction between zinc and hydrochloric acid is best described as

A. an acid-base reaction

B. a precipitation reaction

C. a redox reaction

D. a gravimetric reaction


The next two questions relate to the following information

Question 11

The number of different IH environments in this molecule would be

A. 2

B. 3

C. 4

D. 5

Question 12

The molecule is formed from

A. ethanoic acid and ethanol

B. ethanoic acid and I-propanol

C. propanoic acid and ethanol

D. propanoic acid and I-propanol

Question 13

Which of the following statements about Atomic Absorption Spectroscopy (AAS) is correct?

A. It is an effective qualitative technique but it cannot be used for quantitative analysis.

B. It measures the wavelengths of light emitted when electrons fall back to their ground state.

C. White light is shone through a vaporised sample to determine which wavelengths are absorbed.

D. The wavelength of light used matches one of the wavelengths emitted when the sample is analysedby a flame test.


Question 14


Different indicators change colour over different pH ranges and it is important to choose the correctindicator to obtain an accurate result in a titration.

If a particular weak base is added to a strong acid, the following curve is obtained showing the variationof pH with the volume of weak base added.

14

12

10

8

pH

6

4

2

o

-~

)~

~

o 10 20 30

volume of weak base added in mL

Which of the indicators below would not be the best choice to use in the titration?

A. methyl red

B. bromothymol blue

C. phenol red

D. phenolphthalein

Question 15

Which aqueous solution turns phenolphthalein pink / red?

A. HCI

B. NaCI

C. NaOH

D. CH30H


Question 16


When the oxide, Ch07 is added to water, a reaction takes place which is not a redox process. Theproduct(s) ofthe reaction could be

A. HC104

B. HOCl

C. Ch and O2

D. HCl and O2

Question 17

The Avogadro Constant is the same as the number of

A. molecules in 16 g of oxygen gas

B. electrons in 1 g of hydrogen gas

C. atoms in 24 g of carbon

D. .ions in 1 L of 1.0 M sodium chloride solution

Question 18

Which line in the table correctly describes reactions I and IT?

CH3CH= CH2

Reaction I lCH3CH2CH20H

Reaction IT l

Reaction I Reaction IT

A. hydration oxidation

B. hydration reduction

C. hydrolysis oxidation

D. hydrolysis reduction


Question 19


The label of a brand of sauce states that it has 1051 mg of sodium per 100 g. Assuming all of the sodiumions in the sauce are from added sodium chloride, the mass (in grams) of sodium chloride in a 1.0 g serveof the sauce would be closest to

A. 0.011

B. 0.027

C. 0.11

D. 0.27

Question 20

In a titration of a strong base with a strong acid, the following procedure was used

1. A burette was rinsed with water and then filled with the standardised acid.

2. A pipette was rinsed with some base solution.

3. A conical flask was rinsed with some base solution.

4. A pipette was used to transfer a measured volume of base solution into the conical flask.

5. Indicator was added to the base sample and it was titrated to the endpoint with the acid.

Which of the following statements is correct?

A. The calculated base concentration will be correct.

B. The calculated base concentration will be too low.

C. The calculated base concentration will be too high.

D. No definite conclusion can be reached about the base concentration.

END OF SECTION A


SECTION B - Short answer questions


Instructions for Section BAnswer all questions in the spaces provided.

To obtain full marks for your responses you should

• give simplified answers with an appropriate number of significant figures for all numerical questions;unsimplified answers will not be given full marks.

• show all working in your answers to numerical questions. No credit will be given for an incorrectanswer unless it is accompanied by details of the working.

• make sure chemical equations are balanced and that the formulas for individual substances include anindication of state; for example, Hig); NaCI(s)

Question 1

The following unbalanced equation partially describes the process that occurs when potassium bromatesolution, KBr03(aq), is mixed with a solution of oxalic acid, (COOH)2 (aq).

a. i. What is the oxidation number of bromine in Br03-?

ii. Give the formula of the species being oxidised. Explain your response.

I + 1 = 2 marks

b. i. Write the balanced oxidation half-equation.

ii. Write the balanced reduction half-equation

iii. Write the balanced overall equation for the reaction

I + 1 + 1 = 3 marks

Total 5 marks


Question 2


The mining industry makes extensive use of atomic absorption spectroscopy to analyse mineral samples. Inan analysis of ore samples from a particular mine, the nickel content was to be determined.

Initially, some standardised nickel solutions were prepared and their absorbance measured. The followingtable shows the absorbance vs concentration of some standard samples containing nickel ions.

Absorbance Nickel content (mgL-1)

0 0

0.25 5.00 x 102

0.50 1.00xl03

0.75 1.50 x 103

1.0 2.00 X 103

a. Which of absorbance or nickel content is the dependent variable? Briefly explain your answer.

1 mark

b. On the axes provided, plot a fully labelled graph of absorbance against concentration.

3 marks


c. An ore sample was prepared for analysis by• digestion of 1.35 g of ore in acid and made up to 10.0 mL.• this solution was then diluted with distilled water to 100 mL.

The diluted sample gave an absorbance reading of 0.62.

i. Determine the concentration of nickel ions, in mglL, in the diluted sample.

ii. Determine the mass of nickel, in mg, in the ore sample

iii. Calculate the percentage by mass of nickel in the sample.

1 + 2 + 1 = 4 marks

d. Explain why the ore sample had to be diluted.

1 mark

Total 9 marks


Question 3

The structure of a dipeptide is shown below.


CH HI 3 0 I

H"" / C

1",II / C

1'" ~O

N C-N C

H/ H I CHz \H I OH

OH

a. Circle the peptide link.

b. Draw the stl1lcture of and name the amino acids from which it has been synthesised.

1 mark

4 marks

c. i. Draw the structure (showing all bonds) of one of these amino acids at neutral pH

1 mark

ii. Draw the structure of the other amino acid (showing all bonds) at low pH.

1 mark

Total 7 marks


Question 4

An alkene has the following structure


a. Give the systematic name of the alkene.

b. The alkene is reacted with HBr(g). Name the type of reaction occurring.

c. Draw the structure of and name any possible product(s).

1 mark

1 mark

4 marks

Total 6 marks


Question 5


A triglyceride, with a molar mass of 884 g mor l, is formed by reacting glycerol with an excess of linoleic

acid.

a. How many peaks would be expected in the l3C NMR spectrum of glycerol? Explain your answer.

2 marks

b. Draw a representation of the triglyceride showing all bonds except for the fatty acid residues.

2 marks

c. How many C/C double bonds are present in each molecule oflinoleic acid? Explain your answer.

1 mark

d. 1.00 g of the triglyceride is reacted with excess Brz, calculate the mass of Brz needed for thisreaction.

3 marks

e. If the lipid had been made from oleic acid, ClsH340Z, without further calculation state how youexpect the mass of Brz to differ from your answer in d and explain your reasoning.

I mark

Total 9 marks


Question 6


A student is provided with samples of 1- propanol and ethanol and is asked to synthesise a pure sample ofthe liquid ethyl propanoate.

a. Create a reaction pathway to show how the student might produce this compound using semistructural formulae of organic reactants and products. Include names of any inorganic reagents thatwould be required.

5 marks

b. Give the name of the process which would enable the mixture of liquids at the end of the reaction tobe treated so that pure ethyl propanoate can be obtained.

1 mark

c. Explain how IR spectroscopy could be used to distinguish between pure ethyl propanoate andethanol.

2 marks

Total 8 marks


Question 7


A student prepared a sample of aspirin, C9Hg0 4 by reacting salicylic acid, C7H60 3, with acetic anhydride,C4H60 3, according to the equation

The student used 3.00 g of salicylic acid with 4.00 g of acetic anhydride to obtain 2.0 g of aspirin.

a. Calculate the theoretical mass of aspirin that should have been obtained.

5 marks

b. Determine the percentage yield of aspirin in this experiment to the appropriate number of significantfigures.

2 marks

Total 7 marks


Question 8


A compound is an ester with the empirical formula C2H40 and a molar mass of 88.

a. Determine the molecular formula of the compound.

1 mark

b. Draw four structures (show all bonds) for esters which satisfy these requirements.

4 marksThe mass spectrum of the compound is shown below.

100 %

-

-

I I I I

2957

27

I I I I I I I

59

I I I I

88

I I I

10 20 30 40 50

mass I charge ratio

60 70 80 90

c. Circle any structure you drew in b which could give this mass spectrum.

d. Identify the fragments that give rise to the peaks at 29,57 and 59.

2 marks

3 marks

Total 10 marks


Question 9

Flowers produce nectar which contains a mixture of sugars such as glucose and sucrose.

a. 1. To which family of compounds do glucose and sucrose belong?

ii. Name a digestible polymer which also belongs to this family.

1 + 1 = 2 marks

b. Glucose can be broken down to produce alcohol.

1. Name this type of chemical reaction.

ii. Write a balanced equation for the reaction.

1 + 2 = 3 marks

Total 5 marks

END OF EXAMlNATION

STAY

STAV Publishing 2009

PUBLISHING

CHEMISTRYUnit 3

Trial ExaminationSOLUTIONS BOOK

Published by STAV Publishing. STAV House, 5 Munro Street, Coburg VIC 3058 Australia.Phone: 61 + 3 9385 3999 • Fax: 61 + 3 9386 6722 • Email: [email protected] Website: http://www.sciencevictoria.com.au/stavpublishing© STAV PUblishing April 2009ABN 61 527 110 823

All rights reserved. Except under the conditions described in the Copyright Act 1968 of Australia and subsequent amendments, no part of this publicationmay be reprinted, reproduced or utilised in any form or by any electronic, mechanical, or other means, now known or hereafter invented, includingphotocopying and recording, or in any other information storage or retrieval system, without permission in writing from the publisher.

© STAV Publishing 2009 1 Chemistry Unit 3 Solutions

Use this page as an overlay for marking the multiple choice answer sheets. Simplyphotocopy the page onto an overhead projector sheet. The correct answers are open boxesbelow. Students should have shaded their answers. Therefore, any open box with shadinginside it is correct and scores 1 mark.

ONE ANSWER PER LINE ONE ANSWER PER LINE

1 • D 11 D •2 D • 12 D •3 D 13 D4 D 14 D5 D • 15 D •6 D 16 D7 D 17 • D8 • D 18 D9 D • 19 • D10 D • 20 D •


SECTION A (Total 20 marks)

2 Chemistry Unit 3 Solutions

OR

1. B 2. C 3. D 4. D 5. C6. D 7. A 8. B 9. C 10. C11. C 12. C 13. D 14. D 15. C16. A 17. B 18. A 19. B 20. C

Comments for Section A answers

Question 1

CH3CH2CH2CCI = CHCH3

Counting from the right gives the double bond at the 2nd C atom and the CIon the 3rd C atom. Correctanswer is B.

Question 2From the data book the structure of tyrosine is shown below.

'(----.\C,'H2 \~ ),"-~~l

H2-N'-rn-COOH

The benzene ring only has four H atoms but 6 C atoms. This gives 11 H atoms altogether. Correct answeris C.

Question 3o

II0-/ I"'"

6- 0

Each phosphate group bonds to two deoxyribose (sugar) units to make the backbone on DNA. This leavesone charged 0 atom. Hence DNA carries a negative charge. Correct answer is D.

Question 4From the structures provided in the data book, guanine has the molecular formula CsHsNsO and cytosinehas the molecular formula C4HsN30. This is a difference of CN2which is 40 g. Correct answer is D.

Question 5Methanol is CH30H and stearic acid from the data book is CH3(CH2)16COOH:The biofuel is the ester CH3(CH2)16COOCH3. Correct answer is C.

Question 6n Mg(OH)2 in 10 mL = m/M = 400 xlO-3/ 58.3 = 6.9 x 10'3 moln (OH-) in 10 mL = 2 x n Mg(OH)2 = 13.8 X 10'3 moln (OH-) in 1.0 L = 13.8 X 10-3x 1000/10 = 1.38 mol = 1.4 mol Correct answer is D.


Question 7n(Cr) = 0.250 mol

3

n(MgClz) = 0.125 mol M(MgClz) = 95.3 g mor l

Chemistry Unit 3 Solutions

m(MgClz) = n x M = 0.125 x 95.3 = 11.9 g Correct answer is A.

Question 8n(Zn) = m/M = 3.27 / 65.4 = 0.0500 mol

Conditions given are at SLC. Vm = 24.5 L mor l

V(H2) = n'x Vm = 0.0500 x 24.5 = 1.23 L. Correct answer is B.

Question 9n(Zn2+) = n(Zn) [ Zn2+J = n / V = 0.050 / 0.250 = 0.200 M Correct answer is C.

Question 10Zn has been oxidised to Zn2+. H+ ions have been reduced to H2 .

The reaction is a redox reaction. Correct answer is C.

Question 11Draw out the structure of the ester. All ofthe individual groupings of the hydrogen nuclei are in differentenvironments. There are four different lH environments. Correct answer is C.

Question 12The molecule CH3CH2COOCH2CH3 is an ester formed from CH3CH2COOH (propanoic acid) andHOCH2CH3 (ethanol). Correct answer is C.

Question 13AAS uses a particular wavelength which is absorbed to determine quantitative information. Wavelengthsabsorbed are the same as wavelengths emitted. Correct answer is D.

Question 14The indicator should change colour with the sharpest possible rise in pH. From the curve this looks likebetween 6 to 8.From the data bookmethyl red changes colour between 4.2 and 6.3bromothymol blue changes colour between 6.0 and 7.6phenol red changes colour between 6.8 and 8.4phenolphthalein changes colour between 8.3 and 10The only indicator that changes outside the entire range is phenolphthalein. Correct answer is D.

Question 15The only base in the group is NaOH. Correct answer is C.


Question 16Ch07 has Cl in oxidation state +7. HCl04 has Cl in oxidation state +7. Correct answer is A.

Question 1716 g of Oz = Y2 a mole of molecules1 g of Hz = Y2 mol of Hz but 1 mol ofH atoms. Each H atom has one electron. ie 6.0 x 1023 ions24 g C is 2 mol of Clmol ofNaCl has 2 mol of ions. Correct answer is B.

Question 18I is an addition reaction but can also be referred to as hydration as a water molecule is added across thedouble bond and II is an oxidation reaction. Correct answer is A.

Question 19n(Na)=m/M = 1051 x10·3 /23.0= 0.0457 mol in 100g

m(NaCl) = n x M = 0.0457 x 58.5 = 2.67 in 100 g

in 1.0 g, m(NaCl) = 0.0267 g. Correct answer B.

n(Na) = n(NaCl) = 0.0457 mol

Question 20The conical flask should not have been washed with base solution but with de-ionised water. More acidwill be needed. The number of mole of base will be higher and therefore its concentration will appearhigher. Correct answer is C.


SECTION B - Short answer questions

Question 1 (5 marks)


a. i. +5 1 mark ii. (COOH)2 Cis oxidised from +3 to +4 state 1 mark

b. i. (COOH)2 (aq) ---7 2 CO2(g) + 2H\aq) +2e' 1 mark

iii. 3(COOH)2 (aq) + Br03- (aq) ---7 6 CO2 (g) + Br - (aq) + 3 H20(l) 1 mark

Question"2 (9 marks)

a. The absorbance depends on concentration. The dependent variable is plotted on the y axis. 1 mark

b. Correct plot of graph 2 marks; labelling of axes 1 mark

c. i. 1.24 x 103mg / L 1 mark

11. therefore 124 mg in 100 mL 1 mark therefore 124 mg in original 1.35 g 1 mark

iii. % Ni = (124 x 10'3) x 100 /1.35 = 9.19 % 1 mark

d. All the light could have been absorbed giving a false reading. 1 mark


a.H

Ic~ ~oI c~

CH2 \

I O-H

OH

1 mark

b.CH-OH 1 markI -

~-CH-COOH

alanine 1 mark senne 1 mark


c. i. H

H~ I/HC

H~ I ~O orH-N-C-C /

/+ I \HH 0-

ii.H

H~ I/HC or

H", I ~OH-N-C-C/

/+ I \O-HHH


H

H~ I/O-HC

H", I ~OH- N-C -c /

/+ I \H H 0-

H

H~ I/O-HC

H", I ~OH-N-C-C/

H/+ I \O-HH

1mark

1 mark

a. 2-methylpent-2-ene or 2-methyl-2-pentene 1 mark

b. Addition reaction.

c.

1 mark

2-methyl-3-bromopentane 1 mark


2-bromo-2-methylpentane 1 mark

a. Glycerol shows only 2 peaks in the l3C spectrum. 1 mark. Two of the carbons have identicalenvironment 1 mark.

b.o

H", IIC-O-C-C H

H---- 17 31

oII

H- C-0-C-C17

H31

o

II/C-0-C-C

17H

31

H IH

correct overall structure 1 markall the relevant bonds shown 1 mark


c. From the data book, linoleic acid has the formula C17H31 COOH. Compared with stearic acid,C17H3SCOOH, which only has C/C single bonds, linoleic acid must have two C/C double bonds.

1 markd. n(triglyceride) = m/M = 1.00/ 884

n(Br2) / n(lipid) = 6 / 1 1 mark

0.00113 1 mark

n(Br2) = 6 x 1.00 x 160/ 884 = 1.08 g 1 mark

e. It would be approximately half of the previous answer as there are only three C/C double bonds.1 mark


a. Oxidise propan-l-ol to propanoic acid using a suitable oxidising agent1 mark for choosing to oxidise propan-l-ol and 1 mark for H+ / Cr2072- or equivalent

-7 CH3CH2COOH 1 mark for both correct semi-structural formulae

concentrated H2S04

1 mark for the correct ester and 1 mark for the concentrated sulfuric acid

No need to balance equation. No need to write the structure of the alcohol in reverse.

Note: A student who chooses to oxidise the incorrect alcohol but has everything else correct shouldscore 4 marks

b. Using fractional distillation 1 mark

c. The ester would have a C=O stretch around 1700 cm 1 mark but no broad OH stretch around 3300cm.

The ethanol would not have a C=O stretch around 1700 cm but has a broad OH stretch around3300 cm. 1 mark


1 mark for all the molar masses which need to be used for answering the question

1 mark for calculating moles ofboth salicylic acid and acetic anhydride correctly.

1 mark for recognising that C7H60 3 is the limiting reagent

b. % yield = 100 x 2.0 /3.91 = 51.2 % = 51 % 1 mark (2 sf) 1mark




a. The ester must have a molecular formula of C4Hg0 2 1 mark

b. It could have the following semi structures

1 mark

1 mark

iii. HCOOCH2CH2CH3 1 mark

iv. HCOOCH(CH3)2 1 mark

c. The peak at 59 suggests a fragment of 29 has been lost - possibly - CH2CH3 1 markcould be circled in either i, ii, iii (accept any 2). If the student has looked at the whole spectrum theymight conclude it can only be i. 1 mark

d. 59 could be (CH3COOt57 could be (CH3CH2COt29 could be (CH2CH3t

1 mark1 mark1 mark

There may be other possibilities. Accept any reasonable answer. Deduct a mark only once foromission of a positive charge.


a. i. carbohydrates or polysaccharides 1 mark

ii. starch or glycogen 1 mark

b. i. oxidation or redox I mark

END OF SUGGESTED SOLUTIONS

STAV 2009 Chemistry Exam 1

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