mock examination (2016/2017) chemistry paper 1...

1MT/2016-2017/S4-CHEM 1

Mock Examination

(2016/2017)

CHEMISTRY PAPER 1

SECTION B: Question-Answer Book B

Date :

Time :

This paper must be answered in English

INSTRUCTIONS FOR SECTION B

(1) Write your name, class and class number in the spaces provided on page 1.

(2) Refer to the general instructions on the cover of the Question Book for Section A.

(3) Answer ALL questions. Write your answers in the spaces provided in this Question-Answer Book. Do not write in the margins. Answers written in the margins will not be marked.

(4) An asterisk (*) has been put next to the questions where effective communication is assessed.

(5) Supplementary answer sheets will be supplied on request. Write your name, class and class number and fill in the question number on each sheet, and fasten them with a string INSIDE this Question-Answer book.

Name:

Class:

Class No:

MC (36 marks)

LQ (84 marks)

Total (120 marks)

B 2016 – 2017 MOCK CHEM

PAPER 1B

Answers written in the margins will not be marked.

/2016-2017/Mock-CHEM 2

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Answer ALL questions. Write your answers in the spaces provided.

1. Alloy is a mixture of metals with other elements. The following diagrams show the structures of ionic crystal

composed of metal ion A and bromide ion, pure metal A and alloy containing metal A respectively.

structure of ionic crystal

structure pure metal A

structure of alloy of metal A

(a) Explain whether the above three substances will bend into a desired shape if they are hammered.

Structure of Alloy:

It cannot. As the uniform packing the metal atom is being distorted. The metal atoms of different sizes

cannot slip over each other (1M)

Structure of Metal A

It can. The metal atom pack regularly, once hammered, the atoms can slip over each other without

breaking strong metallic bond (1M)

Structure of the ionic crystal:

It cannot. As the ions once hammered, same charge of ions repel each other, the ionic bond between the

oppositely charged repel each other, thus the ionic bond is broken. (1M)

(3 marks)

(b) Given that metal A is an alkali metal contains five electrons occupied shell. Explain why the size of bromide ion

is larger than metal ion A.

The number of occupied electron shell is the same as metal A ion and bromide ion,

The ratio between the electron to proton is larger in bromide ion than metal ion A. 1

The metal ion A exert a large nuclear charge to electron in outermost shell than bromide,

the greater the attraction, the smaller size of the ion 1

Also accept number of electron > number of proton for bromide ion, the electron – electron repulsion is

larger than the proton – electron attraction, resulted in larger size of bromide ion.

(2 marks)


/2016-2017/Mock-CHEM 3

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2.

Dinitrogen oxide (N2O) and carbon dioxide are green house gases. Answer the following questions regarding to these

two gases.

(a) There is a dative covalent bond in the molecule of dinitrogen oxide. Draw the electron diagram of a dinitrogen

oxide molecule, showing electrons in the outermost shell only.

(1M)

(1 mark)

(b)

(c)

(d)

Describe how a dative covalent bond is formed in a molecule of dinitrogen oxide.

The lone pair of nitrogen atom donates a pair of electrons to the vacant site of oxygen atom. (1M)

(1 mark)

The diagram below is the electron diagram of a nitrogen dioxide (NO2) molecule, showing electrons in the

outermost shell only.

Explain why NO2(g) is more reactive than N2O(g) at room conditions.

The molecule cannot attain octet structure / stable noble gas structure. (1M)

(1 mark)

Dry ice is the solid state of carbon dioxide. Draw the structure of dry ice in the following diagram.

(1M)

(1 mark)


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2. (e) Show dry ice is composed of carbon dioxide and acidic in nature with the help of a labeled diagram of an

experimental set-up.

Set-up: 1M

Test result: 1M

(2 marks)

3. State whether each of the following statements is true or false. Explain your answer in each case.

(a) In the electrolysis of a copper(II) sulphate solution using copper cathode and graphite anode for a certain period

of time, colour intensity of the copper(II) sulphate solution does not change.

False

The Cu2+ in the electrolyte is a stronger oxidizing agent than H+ in electrochemical series.

(1M)

The Cu2+ will be preferentially discharged and is reduced to Cu, and Cu in cathode electrode will

not undergo oxidation to form Cu2+ thus the concentration of Cu2+ is decreased.

(1M)

(2 marks)

(b) Polyethene and ethene can be distinguished by using acidified potassium permanganate solution.

True

Polyethene is a saturated hydrocarbon, while ethene is an unsaturated hydrocarbon posses C=C

1

C=C will undergoes addition reaction with potassium permanganate solution, while polyethene

cannot. Such that the potassium permanganate solution turns from purple to colourless.

1

(2 marks)


/2016-2017/Mock-CHEM 5

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4. A domestic drain cleaner solution contains sodium hydroxide as the active ingredient. A student carried out an

experiment to determine the molarity of sodium hydroxide solution in the domestic drain cleaner. The procedures of the

experiment are shown below.

Step 1: 25.0 cm3 of the domestic drain cleaner solution was made up to 250.0 cm3 in a volumetric

flask. 10.0 cm3 portions of the diluted solution were pipetted into a conical flask.

Step 2: The solution in the conical flask was then titrated against 0.10 M hydrochloric acid using a

suitable indicator

Step 3: The solution required 30.0 cm3 of hydrochloric acid for complete neutralization.

(a) Besides addition of suitable indicators to detect the end-point of the reaction, briefly describe how the end point is

reached for the neutralization between sodium hydroxide and hydrochloric acid.

Use a data logger to monitor the change in temperature of the titration (1M)

The maximum temperature rise indicates the end point of reaction has been reached. (1M)

(2 marks)

(b) Calculate the concentration of sodium hydroxide solution, in g dm－3, in domestic drain cleaner.

(Given that the relative atomic masses of H = 1.0, O = 16.0 and Na = 23.1)

The mole of HCl(aq) used = 0.1 x 30/1000 = 0.003 mol

The mole of alkaline in the conical flask = 0.003 mol 1

The number of mole of alkaline in 250.0 cm3 volumetric flask = 0.075 mol

The molarity of the alkaline in 25.0 cm3 domestic cleaner solution = 3.0 mol dm-3 1

The concentration of NaOH = 120 g dm-3 1

(3 marks)

(c) Given the following materials and apparatus, briefly describe how a 0.10 M hydrochloric acid can be prepared.

(You are NOT required to use all apparatus.)

200 cm3 of 0.4 M hydrochloric acid, 100.0 cm3 volumetric flask, 250.0 cm3 volumetric flask,

25.0 cm3 pipette, 50.0 cm3 burette, distilled water

Transfer 25.0 cm3 of 0.4 M HCl(aq) to a 100.0 cm3 volumetric flask with a 25.0 cm3 pipette. 1

Add distilled water to the volumetric flask until reaching graduation mark. 1

(2 marks)


/2016-2017/Mock-CHEM 6

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*5. Using the molecular formula C5H12O as an example to define the term “structural isomerism”. Hence explain for ONE

difference in physical property and chemical property arisen from the structural isomers of same function group.

Suitable diagram(s) should be included in your answer.

(6 marks)

Students have to use 1o, 2o and 3o alcohol as an example to illustrate the definition of structural isomer. 1

Physical property: Difference in melting point

Owing to the packing efficiency, the branch alcohol pack less compactly resulted in lower melting point

Then the straight chain alcohol butan-1-ol. 1+1

Chemical property: Oxidation with acidified potassium dichromate solution with heating

Only butan-1-ol and butan-2-ol can undergoes oxidation that turn acidified potassium dichromate solution from

orange to green, while methylbutan-2-ol cannot. 1 + 1


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6. Enthalpy change of combustion of butan-1-ol can be determined by direct or indirect methods. The following labelled

diagram show how the enthalpy change of combustion of butan-1-ol can be found by simple calorimetric method in a

school laboratory.

(a) Show the data treatment of the above experimental set-up to illustrate how the enthalpy change of combustion

can be determined.

Measure the maximum temperature rise by extra-polate the graph of temperature against time

Measure the volume of water used as the mass of water used.

Weigh by difference of alcohol being burnt, the divided it with molar mass of alcohol

1M

1M

1M

(3 marks)

(b) The standard enthalpy change of formation (Hf o ) of the following compounds is given. Calculate the standard

enthalpy change of combustion of butan-1-ol.

Hf o / kJ mol1

Standard enthalpy change of formation of butan-1-ol 327.4

Standard enthalpy change of formation of carbon dioxide 393.5

Standard enthalpy change of formation of water 285.8

(393.5 x 4 + 285.8 x 5) + 372.4

= 2630.6 kJ mol1

1

(2 marks)

(c)

(d)

Given the standard enthalpy change of combustion of 2-methylpropan-2-ol is 2643.8 kJ mol1, explain which of

the compounds, butan-1-ol or 2-methylpropan-2-ol, is more energetically stable based on the answer in (b).

Both are structural isomeric to each other, gives the same number of mole and same potential energy CO2(g) and

H2O(l) 1M

Combustion of butan-1-ol is less exothermic than 2-methylpropan-2-ol, so butan-1-ol is of lower potential energy

than 2-methylpropan-2-ol, its more energetically stable. 1M

(2 marks)

Besides heat lost to the surroundings, explain why the determination of the standard enthalpy change of

combustion octan-1-ol using the set-up in (a) will lead to large discrepancies with the theoretical data.

Incomplete combustion (1M)

(1 mark)

thermometer

clamps

metal container

spirit burner

alcohol

water


/2016-2017/Mock-CHEM 8

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7. An ester with a pleasant banana smell is prepared by heating 30.0 cm3 of 3-methylbutan-1-ol with 30.0 cm3 of ethanoic

acid under reflux in the presence of concentrated sulphuric acid.

(a) Write a chemical equation for the reaction involved in the esterification.

(CH3)2CH(CH2)2OH + CH3COOH CH3COO(CH2)2CH(CH3)2 + H2O 1M

(1 mark)

(b) Show ethanoic acid is used in excess in the experiment by calculation.

(Given: density of 3-methylbutan-1-ol = 0.81 g cm－3 , density of ethanoic acid = 1.05 g cm

－3

relative atomic masses: H = 1.0, C = 12.0 and O = 16.0)

Number of mole of 3-methylbutan-1-ol = 20 x 0.81 / 88 = 0.184, 1M

Number of mole of ethanoic acid = 20 x 1.05 / 60 = 0.35 1M

In the reaction, it is one mole of 3-methylbutan-1-ol reacted with 1 mole of ethanoic acid

Ethanoic acid is in excess.

(2 marks)

(c)

Draw a labelled diagram to show the experimental set-up for the synthesis of the ester in a school laboratory.

Reflux Set-up

Chemical used

Deduct marks:

Wrong for

(1) Position of water in and out

(2) Without using anti-bumping granule

(3) Without indication of chemical used.

(2 marks)


/2016-2017/Mock-CHEM 9

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7. (d) The experimental procedures for extracting the ester from the reaction mixture are outlined below.

Step 1: Add ether and distilled water to the reaction mixture and shake the mixture until two

distinctive layers are observed in the separating funnel as shown below.

Step 2: Add excess Na2CO3(aq) in a separating funnel and shake the reaction mixture.

Step 3: Collect the ether layer and discard the aqueous layer.

Step 4: Dry the ether layer by adding excess anhydrous Na2SO4(s).

Step 5: Remove the excess Na2SO4(s) by filtration.

Step 6: Distill the reaction mixture to collect ester product.

(i)

(ii)

(iii)

Name the ionic compound present in aqueous layer after Step 2.

Sodium carbonate, sodium ethanoate (1M or 0)

During the shaking process in Step 2, the tap of the separating funnel should be opened occasionally before

discarding the aqueous layer. Explain the importance of this action.

To release gas (CO2) out, otherwise internal gas pressure to build up in the apparatus (1M)

Based on the extraction procedures, explain why it is important of the ethanoic acid adding in excess rather

than that of 3-methylbutan-1-ol.

Because ethanoic acid can be removed by the addition of base through acid-base reaction while

3-methylbutan-1-ol does not. Otherwise the product isolated will be impure. 1M

(3 marks)

separating funnel

ether layer contains ether, ester and ethanoic acid

aqueous layer contains water and ethanoic acid

tap

stopper


/2016-2017/Mock-CHEM 10

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8. Styrene-acrylates is a synthetic polymer for cosmetic uses. The polymer is derived from styrene and acryliacid as

monomers.

Styrene acryliacid

The linkage of the monomers for forming the polymer is shown below.

(a) Write a chemical equation for the formation of the polymer.

(1 mark)

(b) When the mixture of styrene and acryliacid polymerizes, explain whether the polymer only formed as the above

regular pattern.

The packing of the monomer is a random process. (1M)

(1 mark)

(c)

Give the systematic name of acryliacid.

Methylpropenoic acid (1M)

(1 mark


/2016-2017/Mock-CHEM 11

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9. The table below summarizes the information on three different metals A, B, and C and their compounds. The year of

discovery of the metals in pure state is also given.

Reaction and observation(s). Year of metal

obtained

When A(s) reacted with B(NO3)2(aq), a silvery metal was deposited and the

solution turned from colourless to pale green. Ancient Year

When B(NO3)2(aq) is mixed with NaCl(aq), white precipiptates formed. Ancient Year

When C(s) reacted with hot B(NO3)2(aq), colourless gas bubbles were

observed.

C burnt with a characteristics flame colour.

Year 1807

(a) Arrange metals A, B and C in a descending order of metal reactivity based on the above reaction. Explain your

answer.

Metals A is more reactive than B, as A can displace B from B(NO3)2(aq). 1M

Metal C is more reactive than A, because metal C reacts with water but A does not. 1M

Reactivity series : C > A > B 1M

(3 marks)

(b) When metal B(s) reacts with H2SO4(aq), colourless bubbles evolved at the beginning of the experiment. After a

while, no more bubbles were observed and white solids were formed.

(i)

(ii)

Suggest what B might be.

Pb 1M

Write the chemical equation for the reaction between metal B(s) and H2SO4(aq).

Pb + H2SO4 → PbSO4 + H2 1M

(2 marks)

(c)

A student proposed an alternative approach to determine the metal reactivity by connecting the metal-metal ion

cell. Use suitable chemicals and apparatus to explain how the metal reactivity between A, B and C can be

determined.

1M

The more reactive the metal A of which is the stronger reducing agent to lose electron, is a negative anode

electrode of the cell. 1 M

A positive reading will be resulted. 1 M

(3 marks)

END OF PART I


/2016-2017/Mock-CHEM 12

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10.

Part II

An impure sample of zinc shown in the table below was allowed to react with excess 200 cm3 of 1.0 M dilute

hydrochloric acid at same room temperature and pressure. The volume of gas evolved with time was shown in the

graph below.

mass of the sample

sample (zinc coated with zinc oxide) 0.9 g

(a) Based on the graph above, explain why no gas bubbles were collected at the first few seconds.

The zinc oxide enclosed the zinc, prevents zinc from reacting with acid. 1M

(1 mark)

(b) Calculate the percentage by mass of the zinc oxide in sample.

(Relative atomic mass: H = 1.0 and Zn = 65.4)

120 / 24000 = 0.005 mole 1

Mole of zinc = 0.005 , ∴ mass of zinc = 0.005 x 65.4 = 0.327 g 1

The mass of zinc oxide = 0.9 – 0.327 = 0.573 g

The percentage by mass of zinc oxide = (0.573 / 0.9) x 100 %

= 63.7 % 1

(3 marks)

time / s

vo

lum

e o

f g

as c

oll

ecte

d /

cm

3


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10.

(c) Calculate the pH of the resulting solution when sample A was added to the acid.

(Relative atomic masses: H = 1.0, O = 16.0 and Zn = 65.4)

(d)

Mole of HCl used by zinc = 0.005 x 2 = 0.01 mole

Mole of HCl used by zinc oxide = (0.573 ÷ 81.4) x 2 = 0.014 mole 1

∴ the mole of HCl remained in the solution = (0.2 x 1) – (0.01 + 0.014) = 0.176 mole 1

∴ the concentration of H+ in the solution = 0.176 ÷ 0.2 = 0.88

∴ pH = - log 0.88 = 0.0555 1

(3 marks)

Sketch on the same graph for the progress of gas collected if the experiment is performed at elevated

temperature with the use of 200 cm3 of 0.5 M H2SO4(aq), while other conditions remain unchanged.

(1 mark)


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11.

Suggest a synthetic route, with no more than three steps, to convert compound A into a new organic compound in

which no chiral carbon is formed. For each step in the conversion, give the reagent(s), reaction conditions (as

appropriate) and the structure of the organic product.

(3 marks)

12. (a) Use one experiment to account for the following statements with reference to the TWO characteristics of

transition metals.

“Zinc and copper are both located in area for transition metals in the Periodic Table. However, zinc is usually not

regarded as a transition metals but copper is regarded as a transition metal.”

Using Zn and copper reacts with conc H2SO4(l), different colour of the solutions were observed. 1M

The colour of Zn2+(aq) is colourless, however the colour of Cu2+ is blue. 1M

The oxidation state of Zn is only +2, however the oxidation state of Cu can be +1 or +2 1M

(b)

(3 marks)

Both aluminium oxide and silicon dioxide do not dissolve in water. Explain why the oxides can be distinguished

from one another upon addition of hydrochloric acid but not for sodium hydroxide solution.

Aluminium oxide is amphoteric, it can be soluble in acid or alkaline, as it exhibits both acidic and

alkaline property.

However, silicon dioxide is acidic in nature it reacts with sodium hydroxide as a result silicon dioxide is

soluble in sodium hydroxide only. Moreover, silicon dioxide is not soluble in water due to the breaking

of strong covalent bond between atom is required.

1M

1M

(2 marks)

compound A


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13. Consider the following equilibrium:

2XY2(g) + Y2(g) ⇌ 2XY3(g) H < 0

A mixture of 0.08 mol of XY2(g) and 0.06 mol of Y2(g) was placed in a vessel of volume 2.0 dm3 at temperature T.

When the system had reached equilibrium at 10th minute, it was found that 0.06 mol of XY3(g) was present. No change

was made to the system until 20th minute.

(a) Calculate the equilibrium constant (Kc) for the forward reaction at temperature T.

2XY2(g) + Y2(g) ⇌ 2XY3(g)

Initial mole 0.08 0.06 0

Eqm mole 0.02 0.03 0.06

Eqm conc 0.01 0.015 0.03

Kc = [0.03]2 / ([0.01]2[0.015]) 1M

Kc = 600 mol-1 dm3 1M

(2 marks)

(b) What is the equilibrium constant for the following reaction at temperature T?

XY3(g) ⇌ 2

1Y2(g) + XY2(g)

Kc = 0.0408 mol1/2 dm-3/2 (1M)

(1 mark)


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13.

(c)

Sketch a curve to show the changes of concentration of XY2(g) and Y2(g) from 20th to 30th minute in the

following graph respectively.

(2 marks)

(d) Explain what condition(s) has been changed at the 20th minute.

Increase in temperature (1M)

As it is exothermic reaction, the increase in temperature favors the backward reaction by shifting equilibrium to

left (1M)

(2 marks)

XY3

Y2

XY2


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14.

Compound W with the molecular formula C6H10O3 exists in two isomeric forms of which have the same melting point.

The table below summarize the result of compound W under following chemical tests.

Tests for W Results

Treating with Br2(l) W decolorize brown Br2(l).

Treating with H2SO4(aq) upon heating Two organic compounds contain same number of

carbon atoms are formed.

Treating with acidified K2Cr2O7(aq) with

heat

W turns K2Cr2O7(aq) from orange to green. The

product reacts with Mg(s) to give colourless bubbles.

(a)

(b)

Deduce the structure of compound W. (Three dimensional structure is NOT required)

W have the functional group of C-C double bond which undergoes addition reaction to decolorize KMnO4(aq)

1M

W is an ester, undergoes acid hydrolysis , the carbon number of the W is decreased. 1M

W should have the hydroxyl functional group, however, this should be the primary or secondary alcohol to

undergo oxidation by acidified K2Cr2O7(aq) 1M

The structure :

1M

(4 marks)

Suggest ONE daily application of compound W.

Food flavoring 1M

(1 mark)

END OF PART II

END OF PAPER I


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mock examination (2016/2017) chemistry paper 1...

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