QATS Chemistry Trial 2019 Q&A PDF

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Past paper practise from year 12 trials for pre-semester work...

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Student Name:……………………………

2019 Higher School Certificate Trial Examination

Chemistry General Instructions      

Reading time – 5 minutes Working time – 3 hours Write using black pen Draw diagrams using pencil NESA-approved calculators may be used Three data sheets and a Periodic Table are provided at the back of this paper

Total marks: 100 Section I – 20 marks  Attempt Questions 1-20  Allow about 35 minutes for this section Section II – 80 marks  Attempt Questions 21-32  Allow about 2 hours and 25 minutes for this section

Disclaimer Every effort has been made to prepare this Examination in accordance with the NESA documents. No guarantee or warranty is made or implied that the Examination paper mirrors in every respect the actual HSC Examination question paper in this course. This paper does not constitute ‘advice’ nor can it be construed as an authoritative interpretation of NESA intentions. No liability for any reliance, use or purpose related to this paper is taken. Advice on HSC examination issues is only to be obtained from NESA. The publisher does not accept any responsibility for accuracy of papers which have been modified. CHEMTR19_EXAM

1

Section I – 20 marks Attempt Questions 1-20 Allow about 35 minutes for this section Use the multiple-choice answer sheet provided for Questions 1-20 Select the alternative A, B, C or D that best answers the question. Fill in the response oval completely. Sample 2 + 4 = (A) 2 (B) 6 (C) 8 (D) 9 A B C D If you think you have made a mistake, put a cross through the incorrect answer and fill in the new answer. A B C D If you have changed your mind and have crossed out what you consider to be the correct answer, then indicate this by writing the word correct and drawing an arrow as follows: correct

A

1

2

B

C

D

An anion which forms precipitates with solutions of barium ions, calcium ions, silver ions and lead (II) ions is A.

Cl-

B.

NO3-

C.

CH3COO-

D.

SO42-

Which of the following compounds can be derived both from fossil fuels and from biomass materials? A.

Ethanol

B.

Octane

C.

Glucose

D.

Cellulose

CHEMTR19_EXAM

2

3

Three solutions of acids, HX, HY and HZ, are represented by the following diagrams. For clarity, water molecules have not been shown.

The acids, in order of increasing acid strength, are

4

A.

HX, HY, HZ

B.

HZ, HX, HY

C.

HX, HZ, HY

D.

HY, HZ, HX

Consider the following organic compounds: I – CH3CH2COOH II – CH3COCH3 III – CH3CH2CHO

Which of the following statements is correct?

A.

Compounds I, II and III belong to the same homologous series.

B.

Compound I has the lowest boiling point.

C.

Compounds II and III have the same molecular formula.

D.

Compounds I and III would combine to form an ester and water in the presence of concentrated sulfuric acid.

CHEMTR19_EXAM

3

5

6

Which of the following shows the product(s) of reaction of but-1-ene with water, in the presence of an acid catalyst? A.

Butan-1-ol only.

B.

Butan-2-ol only.

C.

A mixture of butan-1-ol and butan-2-ol.

D.

A mixture of butan-1-ol and butan-4-ol.

The pH of a 0.0001 mol L-1 solution of a monoprotic acid was measured by a student and found to be 4. What proportion of the acid molecules has been converted to ions? A.

0%

B.

4%

C.

96%

D.

100%

7

The compound shown above is A.

2-chloro-3,3-difluoropropane

B.

3-chloro-1-fluoropropane

C.

3,3-difluoro-1-chloropropane

D.

3-chloro-1,1-difluoropropane

CHEMTR19_EXAM

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8

9

Which of the following organic compounds is most basic? A.

Ethane

B.

Ethanol

C.

Ethanamide

D.

Ethanamine

At 100°C, the equilibrium constant for the reaction below is 0.48. N2O4 (g)

2NO2 (g)

Keq = 0.48

In an experiment it was found that the concentration of N2O4 (g) was 0.20 mol/L. Calculate the concentration of NO2 (g) in this equilibrium mixture, in mol/L.

10

A.

0.096

B.

0.31

C.

0.24

D.

0.48

Which is the INCORRECT statement about the reaction when liquid ethanol burns in air? A.

The enthalpy and entropy changes for the reaction are both negative.

B.

The reaction is described as combustion.

C.

The reaction does not reach equilibrium and the system is classified as open.

D.

The enthalpy change is negative and gases form.

CHEMTR19_EXAM

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11

During a spectrophotometric analysis, a chemical of concentration 0.85 M was found to have an absorbance of 0.63. The path length of the cell was 1.5 cm. What is the molar absorptivity constant of this chemical (in M-1cm-1)?

12

A.

0.36

B.

0.49

C.

2.0

D.

2.8

During a precipitation titration using the Mohr method, a 20.0 mL sample of a solution containing chloride ions was titrated with 31.5 mL of 0.150 mol/L AgNO3 to reach the end-point. Calculate the mass of chloride ions present in the original sample.

A.

0.00473 g

B.

0.0315 g

C.

0.168 g

D.

0.236 g

CHEMTR19_EXAM

6

13

The diagram below represents the titration curve for the reaction between an acid and a base.

The equation that best represents the reaction described by the titration curve is

14

A.

HCl (aq) + NH3 (aq)  NH4Cl (aq)

B.

HCl (aq) + NaOH (aq)  NaCl (aq) + H2O (l)

C.

CH3COOH (aq) + NH3 (aq)  CH3COONH4 (aq)

D.

CH3COOH (aq) + NaOH (aq)  CH3COONa (aq) + H2O (l)

Which graph best represents the electrical conductivity changes that occur when an aqueous solution of acetic acid is titrated with an aqueous solution of sodium hydroxide, NaOH?

CHEMTR19_EXAM

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15

16

What is the pOH of the solution formed when 20.00 mL of 0.250 mol/L HCl is mixed with 80.00 mL of 0.350 mol/L NaOH solution at 25°C? A.

0.638

B.

1.638

C.

12.362

D.

13.362

The diagram below shows a mass spectrum for an alkane.

Which alternative correctly summarises the information from this spectrum? Parent ion

Base peak

Formula of alkane

A.

30

14

CH4

B.

28

30

C2H6

C.

30

28

C2H6

D.

28

14

CH4

CHEMTR19_EXAM

8

17

The diagram below shows an infrared spectrum of an organic compound.

The compound analysed was

18

A.

butane

B.

butan-1-ol

C.

butan-2-ol

D.

butanoic acid

The equilibrium constant for the reaction below has an equilibrium constant K1. H2 (g) + I2 (g)

2HI (g)

K1 = 159 at 500K

At the same conditions of temperature and pressure, what is the equilibrium constant for the reaction: HI (g)

½ H2 (g) + ½I2 (g)

A.

0.00629

B.

0.0793

C.

12.6

D.

79.5

CHEMTR19_EXAM

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19

When a sample of NO2 (g) is placed in a container, the following equilibrium is rapidly established: 2NO2 (g)

N2O4 (g)

If this equilibrium mixture is a darker colour at high temperatures and at low pressures, which of these statements about the reaction is correct?

20

A.

The reaction is exothermic and NO2 is darker in colour than N2O4.

B.

The reaction is exothermic and N2O4 is darker in colour than NO2.

C.

The reaction is endothermic and NO2 is darker in colour than N2O4.

D.

The reaction is endothermic and N2O4 is darker in colour than NO2.

The Ksp of Ca(OH)2 at 25°C is 5.02 x 10-6. What is the molar solubility of calcium hydroxide at this temperature? A.

1.71 x 10-2

B.

1.08 x 10-2

C.

2.24 x 10-3

D.

5.06 x 10-4

CHEMTR19_EXAM

10

Chemistry Section II – 80 marks Attempt Questions 21-32 Allow about 2 hours and 25 minutes for this section. Answer the questions in the spaces provided. These spaces provide guidance for the expected length of response. Show all relevant working in questions involving calculations. Extra writing space is provided on pages 34 to 37. If you use this space, clearly indicate which question you are answering.

CHEMTR19_EXAM

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Question 21 (7 marks) A student carried out an experiment to compare the energy changes when solid ionic compounds dissolve in water. (a)

The student observed that the temperature fell when potassium chloride dissolved but rose when sodium hydroxide dissolved. Explain these observations, by discussing the processes involved in the dissolution of ionic substances in water. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

Question 21 continues on the next page

CHEMTR19_EXAM

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3

Question 21 (continued) (b)

“The dissolution both of potassium chloride and of sodium hydroxide occur spontaneously.”

2

Justify the spontaneity of these physical processes in terms of the changes in enthalpy, entropy and Gibbs free energy. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

(c)

Some small crystals of copper sulfate solid were observed in a beaker which contained a saturated solution of copper sulfate. The beaker was covered (so that water could not evaporate) and the beaker and cover were weighed. Over a period of time, the shape of the crystals changed but the weight of the beaker and its contents did not change. Explain these observations. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

CHEMTR19_EXAM

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2

Question 22 (7 marks) Nitrogen monoxide, chlorine and NOCl form an equilibrium gaseous mixture: Cl2 (g) + 2NO (g)

2NOCl (g)

The graph below shows the changes in concentration of the three species over time.

Cl2 (g) + 2NO (g)

2NOCl

(a)

On the graph above, identify A, B and C as Cl2, NO and NOCl.

1

(b)

Explain the change that was made to the reaction conditions at time t = 8.5 min.

1

………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

Question 22 continues on the next page

CHEMTR19_EXAM

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Question 22 (continued) (c)

Use data from the graph to calculate the equilibrium constant for the reaction (as written in the given equation) at time t = 6 min.

2

Assume that the initial concentration of reactant C at t = 0 min is 8.5 x 10-2 mol L-1. ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

(d)

Will the equilibrium constant at t = 12 min be the same as at t = 6 min? Explain your response.

2

………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

(e)

Will the presence of a catalyst impact on the equilibrium in any way? Explain your response.

1

………………………………………………………………………………………… ………………………………………………………………………………………… …………………………………………………………………………………………

CHEMTR19_EXAM

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Question 23 (7 marks) (a) Using IUPAC nomenclature, name the compounds shown below.

Compound 1

Compound 2

3

Compound 3

Compound 1 …………………………………………………………………………… Compound 2 …………………………………………………………………………… Compound 3 ……………………………………………………………………………

(b) Compare the intermolecular forces in the above 3 molecules and predict the order of boiling points (lowest to highest) of these molecules. Explain your prediction.

4

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

CHEMTR19_EXAM

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Question 24 (4 marks) A student was asked to distinguish between colourless organic liquids known to be  butan-1-ol  butan-2-ol  2-methylpropan-2-ol (a)

Explain how the 3 isomers differ in their structures and how these differences allow them to be distinguished.

2

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(b)

Outline the observations which would be made to allow the 3 liquids to be identified. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

CHEMTR19_EXAM

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2

Question 25 (6 marks) (a)

Explain how Aboriginal and Torres Strait Islander Peoples have used the principles of solubility equilibria, when removing toxicity from foods such as cycad fruit.

2

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

(b)

Calculate and compare the solubilities of PbCl2 in water and in a 0.10 mol/L solution of sodium chloride, at 25°C. Ksp PbCl2 = 1.70 x 10-5 ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Question 25 continues on the next page

CHEMTR19_EXAM

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3

Question 25 (continued) (c)

Explain why your 2 answers in part (b) above differ.

1

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

CHEMTR19_EXAM

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Question 26 (3 marks) The diagram shows an experiment related to acid-base reactions. Glass tube Rubber stopper

Cotton wool soaked in HCl soln. (a)

X

Cotton wool soaked in NH3 soln.

Write an equation for the reaction between the gases ammonia and hydrogen chloride and hence identify the solid product X.

1

……………………………………………………………………………………… ………………………………………………………………………………………

(b)

Explain why the reaction of ammonia (gas) and hydrogen chloride (gas) can be classed as an acid-base reaction by the Br฀nsted-Lowry theory, but not by the Arrhenius theory. ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

CHEMTR19_EXAM

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2

Question 27 (9 marks) The table shows the acid dissociation constants at 25ºC.

(a)

Identify the strongest acid in the table and determine the pKa value for this acid.

2

……………………………………………………………………………………… ………………………………………………………………………………………

(b)

Calculate the pH of a 0.10 M solution of nitrous acid.

3

……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ……………………………………………………………………………………… ………………………………………………………………………………………

Question 27 continues on the next page

CHEMTR19_EXAM

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Question 27 (continued) (c) A buffer solution is prepared by combining 100 mL of 0.10 M HNO2 and 100 mL of 0.10 M NaNO2. Calculate the pH of this buffer solution and explain why this solution is classified as a buffer.

………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ………………………………………………………………………………………… ……………...