national senior certificate examination november 2014 · 3.1 a coconut of mass 5,4 kg falls from a...

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NATIONAL SENIOR CERTIFICATE EXAMINATION

NOVEMBER 2014

PHYSICAL SCIENCES: PAPER I

Time: 3 hours 200 marks

PLEASE READ THE FOLLOWING INSTRUCTIONS CAREFULLY 1. This paper consists of: a question paper of 16 pages; a yellow Answer Booklet of 4 pages (i – iv); and a green Data and Formulae Sheet of 2 pages (i – ii).

Please make sure that your question paper is complete.

2. Remove the Data Sheet and Answer Booklet from the middle of this question paper. Write your examination number on the yellow Answer Booklet.

3. Read the questions carefully.

4. Use the data and formulae whenever necessary.

5. Question 1 consists of 10 multiple-choice questions. There is only one correct answer to each

question. The questions are answered on the Answer Sheet inside the front cover of your

Answer Book. The letter that corresponds with your choice of the correct answer must be

marked with a cross as shown in the example below:

A B C D Here the answer C has been marked.

6. Start each question on a new page.

7. It is in your own interest to write legibly and to set your work out neatly.

8. Show your working in all calculations.

9. Where appropriate take your answers to 2 decimal places.

10. Units need not be included in the working of calculations, but appropriate units should be

shown in the answer.

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I of 16

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QUESTION 1 MULTIPLE CHOICE

Answer these questions on the Multiple Choice Answer Sheet in your Answer Book. Make

a cross (X) on the letter of the response which you consider to be the most correct.

1.1 Which one of the following pairs consists of one vector quantity and one scalar

quantity?

A acceleration and velocity

B power and time

C momentum and work

D velocity and impulse

1.2 An athlete runs around the athletics track at a constant speed in an anticlockwise

direction. The athletics track is shown in the diagram below.

Which one of the following statements is true as the athlete runs past point X to Z

via Y? The instantaneous velocity of the athlete is …

A constant between X and Y only.

B constant between Y and Z only.

C constant at all points between X and Z.

D never constant anywhere between X and Z.

1.3 A net force pushes an object horizontally in a straight line from rest. The distance

moved by the object in time ' 't is ' 'x metres. What distance will the same object

move from rest under the action of the same net force in time '2 '?t

A 2x

B 4x

C 2x

D ½ 2x

1.4 The property of a body that causes it to resist a change in its state of rest or uniform

motion is defined as …

A impulse.

B acceleration.

C resistance.

D inertia.



1.5 Which one of the following is NOT a unit of power?

A W

B 1J.s

C 1N.m.s

D 1kg.m.s

1.6 The acceleration due to gravity on the Earth is g. What is the acceleration due to

gravity on a planet which has double the mass of the Earth and half the radius of the

Earth?

A 8 g

B 4 g

C 2 g

D ½ g

1.7 Which one of the following graphs best represents the relationship between the

potential difference (V) across an ohmic conductor and the current (I) in the

conductor at constant temperature?

A B

C D

1.8 Which option correctly gives the energy conversion in the direct current motor as

well as the component(s) connected to the ends of the coil?

Energy conversion Component A Electrical to mechanical Split ring commutator

B Mechanical to electrical Slip rings

C Electrical to mechanical Slip rings

D Mechanical to electrical Split ring commutator



1.9 A coil is rotated in a magnetic field. The graph shows how the magnetic flux ( )

changes with time for one complete rotation of the coil.

Which one of the following graphs shows the corresponding changes in the induced

emf (ε) with time for one complete rotation of the coil?

A B

C D

1.10 The diagram represents 3 energy levels, X, Y and Z, in a certain atom. The energy

difference between levels Y and Z is twice the energy difference between levels X

and Y. If the wavelength of a photon emitted as a result of transition P, from level X

to Y, is , then what is the wavelength of the photon emitted during transition Q,

from level X to Z?

A 2

B 3

C / 2

D / 3

[20]



QUESTION 2 KINEMATICS 2.1 A small block of mass 0,4 kg is released from rest at position A on a track as shown

in the diagram. Position A is 0,8 m vertically above the ground. It takes the

block 3 s to slide from position A to position E where it comes to rest. The length of

the track from A to E is 8,1 m. Position D is 0,3 m vertically above the ground.

There is no friction between positions A and D on the track but there is significant

friction between positions D and E. Air resistance can be ignored. Positions A, B, C,

D and E all lie in the same vertical plane.

Diagram not drawn to scale

2.1.1 Define the terms distance and displacement and hence explain why the

magnitude of the displacement of the block from A to E differs from the

distance travelled by the block from A to E. (4)

2.1.2 Calculate the average speed of the block between A and E. (2)

2.1.3 State the principle of conservation of mechanical energy. (2)

2.1.4 Use the principle of conservation of mechanical energy to calculate the

speed of the block as it reaches point D on the track. (4)

2.1.5 State the work-energy theorem. (2)

2.1.6 Calculate the magnitude of the frictional force acting on the block between

position D and E. The distance between D and E is 3 m. (4)

2.1.7 On the Answer Booklet draw a position-time sketch graph to represent the

horizontal position of the block as measured from A until it stops at position

E. It is not necessary to show any numerical values. It is the shape of your

graph which is important. The times when the block is at position A, B, C, D

and E have been labelled as A B C D Et , t , t , t and t respectively. (4)



2.2 Lucy's doll is suspended by means of two light inextensible strings from the ceiling

in the corner of her room as shown. String A makes an angle of 40 with the ceiling

and string B makes an angle of 90 with the wall. The tension in string A is

12,2 N.

2.2.1 Calculate the magnitude of the vertical component of the tension in string A. (2)

2.2.2 Calculate the mass of Lucy's doll. (4)

2.2.3 Calculate the magnitude of the tension in string B. (2)

[30]



QUESTION 3 FALLING BODIES 3.1 A coconut of mass 5,4 kg falls from a tree and breaks the glass roof of a greenhouse

directly below it. The unbroken coconut continues to fall freely until it hits the

ground. The velocity-time graph below represents the motion of the coconut from

when it left the tree until it hit the ground. Air resistance is negligible.

3.1.1 Calculate the distance fallen by the coconut from when it left the tree until it

hit the glass roof at time t 0,8 s. (3)

3.1.2 Calculate the speed of the coconut at time t 1,7 s as it hits the ground. (4)

3.1.3 Calculate the net force acting on the coconut while it was in contact with the

glass roof. (5)

3.1.4 How does the magnitude of the force exerted by the coconut on the glass

roof compare with the magnitude of the force exerted by the glass roof on

the coconut? Name the law which you used to determine your answer. (2)

3.1.5 Draw an acceleration-time sketch graph to represent the motion of the

coconut over the time period t 0 s to t 1,7 s. It is not necessary to show

any numerical values. (3)

3.1.6 Consider the following information regarding two coconuts X and Y which

fall from different heights:

The mass of coconut X is greater than the mass of coconut Y. As they reach the roof of the greenhouse the momentum of coconut X is

equal to the momentum of coconut Y.

(a) At the roof, is the kinetic energy of coconut X greater than, less than

or equal to the kinetic energy of coconut Y? (1)

(b) Fully explain your answer to Question 3.1.6 (a) making reference to

relevant formulae. (4)



3.2 An object which is dropped on a unknown planet 'P' falls a distance of 11,2 m in its

4th second of motion. There is no air resistance on planet 'P'. Calculate the

magnitude of the acceleration due to gravity on planet 'P'.

(5)

[27]



QUESTION 4 SLIDING BOX EXPERIMENT Tom, Thuli and Tessa conduct an investigation using a box on an inclined plane. Their aim

is to determine how the mass of an object placed on an inclined plane affects the maximum

angle (θ) to which the plane can be tilted before the object just starts to slide down the

plane.

They place an empty box on a flat horizontal track and gradually tilt the track until the box

just starts to slide. They record the angle of the incline (θ) at which this happens.

They then add a 1 kg mass piece to the empty box and repeat the experiment.

They continue to increase the mass of the box by 1 kg at a time and record the angle θ each

time the box starts to slide.

4.1 Name the dependent variable in this experiment. (2)

4.2 Why was it necessary to use the same track and the same box for each experiment? (2)

4.3 Draw a labelled free body diagram to represent the forces acting on the box at rest

on the inclined plane. Show relevant angles and name the forces. (4)

Before conducting their investigation the learners make the following hypotheses:

Tom: "The greater the mass of the box the smaller the angle (θ) of the incline at which the

box will start to slide."

Thuli: "The greater the mass of the box the greater the angle (θ) of the incline at which the

box will start to slide."

Tessa: "The mass of the box will not affect the angle (θ) of the incline at which the box will

just start to slide."

4.4 Use your knowledge and understanding of the forces acting on the box to predict

which learner's hypothesis is correct. Justify your choice by referring to relevant

physics principles and formulae. (5)



4.5 In a different experiment it is found that when the angle of the slope is 36 a box of

mass 12 kg accelerates uniformly from rest down the rough slope of length 18 m at 24,2 m.s .

4.5.1 Calculate the magnitude of the velocity of the box as it reaches the bottom

of the slope. (4)

4.5.2 State Newton's second law. (3)

4.5.3 Calculate the magnitude of the net force acting on the box as it moves down

the slope. (3)

4.5.4 Calculate the magnitude of the frictional force acting on the box. (5)

[28]



QUESTION 5 MOMENTUM Two different balls A and B of masses 250 g and 300 g respectively have a head-on

collision. Ball A is moving to the right at 14 m.s before the collision and ball B is moving

to the left at 16 m.s before the collision. During the collision ball A experiences an

impulse of 11,5 kg.m.s to the left.

5.1 Define momentum. (2)

5.2 Calculate the magnitude and direction of the velocity of ball A immediately after

the collision. (5)

5.3 Calculate the magnitude and direction of the velocity of ball B immediately after the

collision. (5)

[12] QUESTION 6 ELECTRIC FIELD Two positive point charges, A and B, are separated by a distance of 8 mm. The charge on A

is 1 nC and the charge on B is 9 nC.

6.1 Draw an electric field line diagram to represent the field set up by charges A and B. (3)

6.2 State Coulomb's law. (2)

6.3 Calculate the force exerted by charge A on charge B. (5)

6.4 Calculate the number of electrons that charge A lost when it obtained its charge of

1 nC. (2)

6.5 At a distance ' 'x from charge A the magnitude of the resultant electric field due to

charges A and B is zero. Point ' 'x lies on the straight line joining charges A and B.

6.5.1 Define resultant vector. (2)

6.5.2 Define the magnitude of the electric field at a point. (2)

6.5.3 Determine the distance ' 'x from charge A. Show all working/reasoning in

support of your answer. (4)

[20]



QUESTION 7 ELECTRIC CIRCUIT 7.1 An electric circuit is set up as shown in the diagram below. The resistances of the

switch, ammeters and connecting wires are negligible. The voltmeters have very

high resistance.

The battery has an emf (ε) of 12 V and has significant internal resistance (r).

The switch 1S is CLOSED. The ammeter 2A reads 0,2 A and the voltmeter 2V reads 5,5 V. 7.1.1 Define emf. (2)

7.1.2 Calculate the reading on ammeter 1A . (4)

7.1.3 Calculate the resistance of resistor X. (3)

7.1.4 Calculate the total external resistance of the circuit. (3)

7.1.5 Calculate the internal resistance (r) of the battery. (4)

7.1.6 Resistor X is replaced by a new resistor of greater resistance than that of X.

(a) Will the reading on the voltmeter 1V connected across the terminals

of the battery increase, decrease or remain the same? (1)

(b) Explain your answer to Question 7.1.6 (a), making reference to

relevant formulae. (4)



7.2 An electric kettle is rated 240 V; 1 800 W.

7.2.1 What does 'rated 240 V; 1 800 W' mean in regard to how this kettle works? (2)

7.2.2 Calculate the current drawn by the kettle when connected to a 240 V source. (3)

7.2.3 Calculate the cost of using the kettle for 15 minutes if electricity costs R1,40

per kWh. (3)

[29]



QUESTION 8 ELECTRODYNAMICS

A bar magnet is dropped through a coil attached to a digital voltmeter as shown in the

diagram. As the magnet falls through the coil it induces an emf in the coil. The voltmeter is

connected to a computer which plots a graph of the induced emf against time.



8.1 State Lenz's law. (2)

8.2 State the polarity (north or south) of the bottom of the coil as the magnet exits the

coil. (2)

8.3 Draw a labelled free-body diagram to represent the forces acting on the magnet as it

exits the coil. Air resistance can be ignored. (3)

8.4 Define magnetic flux linkage. (2)

8.5 Explain why an emf is induced in the coil. (2)

8.6 State Faraday's Law of electromagnetic induction. (2)

8.7 Why is the magnitude of the maximum induced emf greater as the magnet exits the

coil than when it enters the coil? (2)

8.8 The graph of induced emf vs. time for a magnet falling through the coil has been

reproduced for you three times on your Answer Booklet. On each of the axes

provided on your Answer Booklet, draw a graph to represent the induced emf

against time when each of the three following changes are made to the initial experiment respectively.

8.8.1 The same magnet is dropped from the same height through the same coil

with the NORTH pole entering the coil first. (2)

8.8.2 A STRONGER MAGNET of the same mass and length is dropped through

the same coil from the same height with the south pole entering the coil first. (2)

8.8.3 The same magnet is dropped from the same height through a coil of the

same length but having LESS TURNS. The south pole enters the coil first. (2)

[21]



QUESTION 9 PHOTONS AND ELECTRONS The graph below shows how the maximum kinetic energy of an electron emitted from the

metal cathode of a photoelectric cell varies with the wavelength of the incident radiation.

9.1 Use the graph to determine the maximum kinetic energy of the electron emitted

when the wavelength of the incident radiation is 71,0 10 m. (1)

9.2 Describe the relationship shown in the graph. (2)

9.3 Use your knowledge of the photoelectric effect to EXPLAIN the relationship shown

in the graph. Support your answer with reference to relevant formulae. (3)

9.4 Use the graph to calculate the threshold frequency of the light needed to emit

electrons from the metal cathode of the photovoltaic cell. (4)

9.5 Calculate the work function of the metal used for the cathode of the photovoltaic

cell. (3)

[13] Total: 200 marks


NATIONAL SENIOR CERTIFICATE EXAMINATION NOVEMBER 2014

PHYSICAL SCIENCES: PAPER I

EXAMINATION NUMBER

ANSWER BOOKLET QUESTION 2.1.7 Position-time sketch graph of the horizontal position of the block.

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I – ANSWER BOOKLET Page ii of iv


QUESTION 8.8.1 The same magnet is dropped from the same height through the same coil with the NORTH pole entering the coil first.

Graph of induced emf vs time for a magnet

falling through a coil

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I – ANSWER BOOKLET Page iii of iv


QUESTION 8.8.2 A STRONGER MAGNET of the same mass and length is dropped through the same coil from the same height with the south pole entering the coil first.



NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I – ANSWER BOOKLET Page iv of iv


QUESTION 8.8.3 The same magnet is dropped from the same height through a coil of the same length but having LESS TURNS. The south pole enters the coil first.



NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I – DATA SHEET Page i of ii


EXAMINATION DATA SHEET FOR THE PHYSICAL SCIENCES (PHYSICS)

TABLE 1 PHYSICAL CONSTANTS

NAME SYMBOL VALUE

Acceleration due to gravity g 9,8 m.s-2

Speed of light in a vacuum c 3,0 108 m.s-1

Universal gravitational constant G 6,7 10-11

N.m2.kg-2

Coulomb's constant k 9,0 109 N.m2.C-2

Magnitude of charge on electron e 1,6 10-19

C

Mass of an electron me 9,1 10-31

kg

Planck's constant h 6,6 10-34

J.s

1 electron volt eV 1,6 10-19

J

TABLE 2 PHYSICS FORMULAE

MOTION

v uat or tavv if s vu

2

t or t

vvx

if

2

asuv 222 or xavv if 222 s ut 1

2at2 or 2

21 )( tatvx i

FORCE AND MOMENTUM

maFnet t

pFnet

or vmtFnet

Δp = mv – mu or

f ip mv mv

mvp gw F mg Fmax

f FN

WORK, ENERGY AND POWER

FsW or xFW

or cosW F x t

WP P Fv

mghEp 2

21 mvEk Wnet EK efficiency powerout

powerin

GRAVITATIONAL AND ELECTRIC FIELDS

F Gm1m2

r 2 gG

M

r 2

F kq1q2

r 2 E F

q E kQ

r 2

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER I – DATA SHEET Page ii of ii


ELECTRIC CIRCUITS

I Q

t V W

q

I

VR emf I (Rext r )

......21 RRRS 1 2

1 1 1

p

......R R R

P W

t or W Pt

W VIt or W I 2Rt or W V 2

Rt

P VI or P I 2R or P V 2

R

ELECTRODYNAMICS BAcos

t

Nemf

VpI p VsI s Ns

Np

Vs

Vp

PHOTONS AND ELECTRONS

c f E hf or E hc

(max)KEWE 0 W0 hf0 21

2K(max) maxE mv


NATIONAL SENIOR CERTIFICATE EXAMINATION

NOVEMBER 2014

PHYSICAL SCIENCES: PAPER II

Time: 3 hours 200 marks

PLEASE READ THE FOLLOWING INSTRUCTIONS CAREFULLY

1. This question paper consists of 14 pages, a Data Sheet of 3 pages (i – iii) with data and

formulae and an Answer Sheet. Please remove the Data Sheet and Answer Sheet from the

middle of your paper.

2. Please check that your question paper is complete.

3. ALL the questions in this paper must be answered.

4. Question 1 consists of 10 multiple-choice questions. There is only one correct answer to

each question. These questions are answered on the inside front cover of your Answer Book.

The letter that corresponds with your choice of the correct answer must be marked with a

cross as shown in the example below:

A B C D Here the answer C has been marked.

5. START EACH QUESTION ON A NEW PAGE. 6. Read the questions carefully.

7. Use the data and formulae whenever necessary.

8. Express ALL answers correct to TWO decimal places.

9. An approved calculator (non-programmable, non-graphical) may be used.

10. Show all the necessary steps in calculations.

11. It is in your own interest to write legibly and to set your work out neatly.

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER II Page 2 of 14


QUESTION 1 Answer these questions on the inside front cover of your Answer Book. Make a cross (X) over the

letter of the response which you consider to be the most correct.

1.1 Sodium chloride (NaCℓ) is a solid which is soluble in water. Which one of the following

describes the intermolecular forces that exist between sodium chloride and water in

solution?

A Ion-dipole

B Dipole-dipole

C Ion-induced dipole

D Induced dipole-dipole

1.2 Consider the structure of hexane.

A molecule of hexane is considered to be non-polar. Which one of the following statements

best describes the reason why hexane is non-polar?

A Hexane contains only single bonds between atoms

B The electronegativity difference between C and H atoms is so small as to be

considered non-polar

C Hexane is a linear molecule hence is symmetrical

D The charge distribution of electrons within the hexane molecule is symmetrical

1.3 Hydrogen bonding is a type of intermolecular force that can exist between the molecules of

certain compounds. Which one of the statements below best describes the conditions under

which hydrogen bonding is most likely to occur?

It occurs between …

A small molecules which contain hydrogen atoms

B molecules in which hydrogen is bonded to small atoms with high electronegativity

C large molecules which contain both hydrogen and oxygen atoms

D molecules in which hydrogen is bonded to small atoms with low electronegativity



To answer Questions 1.4 and 1.5, refer to the description below and the graphs A to D that are

provided.

In an experiment to determine the effect of concentration on reaction rate, a constant volume of

HCℓ(aq) of concentration 2 mol·dm–3

is added to a constant volume of Na2S2O3(aq) of varying

concentrations.

1.4 Which one of the graphs A, B, C or D represents the plot of concentration of sodium

thiosulphate (vertical axis) against time taken (horizontal axis) for the reaction?

1.5 Which one of the graphs A, B, C or D represents the plot of reciprocal of time 1

t

(vertical

axis) against concentration of sodium thiosulphate (horizontal axis) for this reaction?

1.6 Consider the following statements with respect to a chemical reaction in a state of dynamic

chemical equilibrium:

I The concentrations of the reactants and products are identical provided the reaction

occurs in a closed system.

II The rates of the forward and reverse reactions are identical provided the reaction

occurs in a closed system.

III The amounts of reactant and product remain unchanged provided the reaction occurs

in a closed system.

Which of the statement(s) above is/are true?

A I only

B II only

C I and III

D II and III



1.7 Consider the following equilibrium established in a closed container at constant temperature.

2NO(g) + 2H2(g) N2(g) + 2H2O(g) ΔH < 0

Which one of the following sets of conditions listed below will produce the lowest yield of

N2(g)?

Pressure Temperature

A Increase by decreasing volume Decrease

B Increase by decreasing volume Increase

C Decrease by increasing volume Increase

D Decrease by increasing volume Decrease

1.8

The compounds X and Y may respectively be:

A CH3CH2CH3 and CH3CH2OOCCH2CH3

B CH3CHCH2 and CH3CH2CH2CH2OOCH

C CH3CHCH2 and CH3CH2CH2OOCCH3

D CH3CH2CH2 and CH3CH2CH2OOCCH3

1.9 Which one of the acids listed below is an example of a polyprotic acid?

A HNO3

B HCℓ C H2SO4

D CH3COOH



1.10 Consider beakers A and B as illustrated below.

20 cm3

of the NaOH(aq) solution in beaker A is added to the NaCℓ(aq) solution in

beaker B. Which one of the following represents the correct calculation for the new concentration of Na

+(aq) ions in beaker B?

A 0 015 0 005

0 17

, ,

,

B 0 015 0 05

0 17

, ,

,

C 0 015 0 05

0 15

, ,

,

D 0 015 0 005

0 15

, ,

,

[20]



QUESTION 2 Calcium chloride is prepared according to the following balanced chemical equation:

Ca(s) + 2HCℓ(aq) CaCℓ2(aq) + H2(g)

Hydrochloric acid is produced for this preparation by the ionisation of hydrogen chloride

gas in water.

2.1 Define the term 'ionisation'. (2)

2.2 Write down a balanced chemical equation for the ionisation of hydrogen chloride

gas in water. (2)

2.3 Name the type of bonding that is present in a molecule of hydrogen chloride. (1)

2.4 Define the term 'electronegativity'. (2)

2.5 Make use of the Pauling scale of electronegativities, as provided in the Periodic

Table, to explain the type of bonding found in hydrogen chloride and crystalline

calcium chloride. (4)

2.6 HCℓ molecules are described as 'dipoles'. Explain what is meant by this term. (2)

2.7 Calcium chloride is soluble in water. The structure of its crystal lattice is broken

down by the water molecules to form aqueous ions in solution.

2.7.1 Name the type of crystal lattice of which calcium chloride is an example. (1)

2.7.2 Using diagrams to illustrate your answer, explain how the crystal lattice of

calcium chloride is broken down during the dissolving process. (4)

[18]



QUESTION 3

In order to investigate the rate of the reaction between a carbonate and an acid, calcium

carbonate and excess of 2 mol·dm-3

hydrochloric acid react in a reaction vessel. The

balanced chemical equation for this reaction is

CaCO3(s) + 2HCℓ(aq) CaCℓ2(aq) + CO2(g) + H2O(ℓ)

Consider the potential energy profile for this reaction as illustrated below:

3.1 The graph has been labelled I – V to represent the various energies that are

illustrated by this energy profile. Identify each of these energies on the profile. (5)

3.2 Using the molecular collision theory, explain why the chemical reaction must gain

potential energy between position A and position B according to the energy profile. (2)

3.3 Provide a name for the position on the graph labelled B and what significant

process takes place at this point. (2)

3.4 Name the type of reaction this graph represents. Explain how you came to this

conclusion. (3)

3.5 The same reaction takes place in the presence of a catalyst. On the potential energy

profile provided, show how the graph would change in the presence of a catalyst. (2)

3.6 How would the presence of a catalyst affect the value of the energy labelled V?

Explain you answer. (3)

[17]



QUESTION 4

Organic chemistry can be described as the study of the structure, properties and reactions

of carbon based compounds. The carbon atom is unique in that it has certain features that

enable it to be the building block of all organic compounds.

4.1 State THREE features of the carbon atom responsible for giving carbon this

uniqueness. (3)

4.2 Draw a Lewis Diagram to represent a molecule of methane. (2)

4.3 Consider the organic compounds represented by the letters A to F listed below:

A CH3CH2CH2Cℓ B CH3COOCH3 C CH3CH2CH3 D CH3CH2CH2OH E CH3CHCH2 F HCOOH

4.3.1 Give the IUPAC name for compound A. (2)

4.3.2 Which formula represents an unsaturated hydrocarbon? Write down only the

correct letter. (1)

4.3.3 Give the names of the homologous series to which

(a) compound A

(b) compound B

belong. (2)

4.3.4 Give the names of the functional groups represented in compounds D and F. (2)

4.3.5 Name the chemical test that is carried out to distinguish between compounds

C and E and list the observations that are made. (3)

4.3.6 Explain, with reference to the relevant intermolecular forces, why

compound D is a liquid at room temperature whereas compound C is a gas. (4)

4.3.7 Write down a balanced chemical equation for the complete combustion of

compound D in oxygen using molecular formulae. (3)



4.4 Consider the following sequence of organic reactions and then answer the questions

that follow. Reactions are labelled A to E.

4.4.1 Which one of the reactions A to E is …?

(Only write down the question number (a) to (d) and the letter you choose

next to it).

(a) a hydrolysis reaction

(b) a hydrohalogenation reaction

(c) a hydrogenation reaction

(d) a dehydration reaction (4)

4.4.2 Provide the chemical formula of a reagent that needs to be added for the

following to occur:

(a) Reaction B

(b) Reaction A (2)

4.4.3 Consider the product formed in reaction E. It is able to exist in two distinct

isomeric forms, one as a positional isomer and the other as a functional

isomer.

(a) Define the term 'isomers'. (2)

(b) State the difference between positional and functional isomerism. (4)

(c) (i) Draw the structural formula of a positional and a functional

isomer of the product formed in reaction E. (2)

(ii) Write down the IUPAC name of each isomer in

Question 4.4.3 (c)(i). (4)

[40]



QUESTION 5

Nitrogen monoxide, released from the combustion engines of motor vehicles, reacts with

oxygen in the atmosphere to produce nitrogen dioxide. This reaction can be simulated in a

closed reaction container of volume 500 cm3 at a temperature of 100

oC. The reaction

reaches equilibrium according to the following chemical equation:

2NO(g) + O2(g) 2NO2(g)

Initially 4 mol of NO and 2,5 mol of O2 were placed in the reaction container with an

unknown amount of NO2. When equilibrium was established, it was found that the

concentration of NO present in the reaction container was 6,5 mol·dm-3

. The equilibrium

constant, Kc, for the reaction at 100 ºC is 0,25.

5.1 State Le Chatelier's Principle. (3)

5.2 A chemical equilibrium occurs in a 'closed system'. State what is meant by the term

'closed system'. (2)

5.3 Calculate the number of moles of NO present at equilibrium. (3)

5.4 Calculate the number of moles of NO that were used up in reaching equilibrium. (2)

5.5 Calculate the concentration of O2 at equilibrium. (4)

5.6 Write down the expression for the equilibrium constant (Kc) for this reaction. (1)

5.7 Using the expression in Question 5.6 to assist in your calculation, determine the

number of moles of NO2 present in the system at equilibrium. (4)

5.8 Calculate the number of moles of NO2 initially present in the reaction container. (4)

5.9 When the temperature of the reaction mixture was increased from 100 oC to 175

oC,

the value of Kc decreased to 0,15. Is the forward reaction exothermic or

endothermic? Explain your answer by using Le Chatelier's principle. (5)

[28]



QUESTION 6 6.1 Indicators (generally represented as HIn) are organic compounds which display

characteristic colours when placed in either an acidic or basic solution. They are

generally weak acids which will ionise in water to reach the following dynamic

equilibrium.

HIn(aq) + H2O(ℓ) H3O+(aq) + In

–(aq)

(yellow) (blue)

Bromothymol blue is an indicator which is yellow in an acidic medium and blue in

an alkali.

6.1.1 Define an acid and a base in terms of the Brønsted-Lowry model. (2)

6.1.2 Indicators are said to be weak acids. State what is meant by the term 'weak

acid'. (2)

6.1.3 By referring to Le Chatelier's principle, explain why bromothymol blue

displays a blue colour when placed in a solution of sodium hydroxide. (4)

6.2 Potassium hydroxide is a strong base that dissociates when placed in water. A

standard solution of potassium hydroxide of concentration 0,45 mol·dm-3

is

prepared in a 250 cm3 volumetric flask at a temperature of 298 K.

6.2.1 State what is meant by the term 'standard solution'. (2)

6.2.2 Write down a chemical equation to show the dissociation of potassium

hydroxide in water. (2)

6.2.3 Calculate the mass of potassium hydroxide used in the preparation of the

standard solution. (5)

6.2.4 The ionisation constant for water (Kw) is 1 × 10-14

at 298 K. Calculate the

concentration of hydronium ions in the potassium hydroxide solution at

298 K. (4)

The standard potassium hydroxide solution prepared in Question 6.2 is used to

determine the unknown concentration of a solution of the weak acid, oxalic acid

(COOH)2. 25 cm3 of oxalic acid is placed in a conical flask with a few drops of

indicator. Exactly 15 cm3 of potassium hydroxide is required to reach the

equivalence point in the titration according to the following balanced chemical

equation:

(COOH)2(aq) + 2KOH(aq) (COOK)2(aq) + 2H2O(ℓ)

6.2.5 State what is meant by the term 'equivalence point' in a titration. (2)

6.2.6 Calculate the number of moles of potassium hydroxide used in the titration. (2)

6.2.7 Calculate the number of moles of oxalic acid that were neutralised by the

potassium hydroxide. (2)



6.2.8 Calculate the unknown concentration of the oxalic acid. (3)

The table below lists the indicators that are most commonly used in a school

laboratory.

Indicator pH range or sensitivity range

Bromothymol blue 6,0 to 7,6

Methyl orange 3,1 to 4,4

Phenolphthalein 8,3 to 10

6.2.9 Explain what is meant by the term 'hydrolysis'. (2)

6.2.10 Which indicator would best be suited for the titration of the potassium

hydroxide solution against the oxalic acid solution? Use your knowledge of

hydrolysis to explain your answer. (4)

[36]



QUESTION 7 Consider the silver-cobalt galvanic cell that is shown in the diagram below which is

operated under standard conditions. The two half cells are connected by a salt bridge which

contains an aqueous saturated solution of potassium nitrate.

7.1 State what is meant by the following terms:

7.1.1 electrolyte (2)

7.1.2 half cell (2)

7.2 State the energy conversion that takes place in a galvanic cell. (2)

7.3 Name a suitable electrolyte that could be used in the silver half cell. (1)

7.4 State what is meant by the term 'standard conditions' with particular reference to the

silver half cell. (2)

7.5 Identify the half cell that is the anode in this galvanic cell. (1)

7.6 Will the electrode in the cathode half cell increase or decrease in mass as the

galvanic cell delivers current? Explain your answer. (3)

7.7 The cell delivers 0,75 A of current for 10 minutes. Calculate the increase or

decrease in mass that the cathode will experience during this time period (assume

concentrations of electrolytes remain constant). (5)

7.8 Write down the net cell reaction for the silver-cobalt galvanic cell. (3)

7.9 With reference to the changing ionic conditions in each half cell, explain how the

salt bridge functions to maintain half cell neutrality within each half cell. (4)

7.10 Aqueous potassium nitrate is a very popular electrolyte used in the salt bridge of a

galvanic cell. Explain the significance of using an electrolyte such as potassium

nitrate. (2)

7.11 With reference to the standard cell conditions, write the full cell notation for this

galvanic cell. (3)

[30]



QUESTION 8 Copper is a metal that can be purified from its ore through an electrolytic technique. The

impure copper ore, known as blister copper, is the anode of the cell while a pure copper

plate is used as the cathode. These electrodes are placed in an electrolyte of aqueous

copper sulphate as shown in the diagram below

Blister copper contains several metal impurities, most commonly silver (Ag), gold (Au),

iron (Fe) and zinc (Zn).

8.1 Name the electrolytic technique described in this question. (1)

8.2 Write down the half reaction that occurs at the cathode. (1)

8.3 Use the table of Standard Electrode Potentials to explain each of the following:

8.3.1 Why copper metal and not water is oxidised at the anode. (2)

8.3.2 With reference to the potential difference applied in the purification, explain

why iron and zinc will be oxidised at the anode, but gold and silver are not. (3)

8.3.3 Why Fe2+

(aq) and Zn2+

(aq) are not reduced at the cathode. (2)

8.4 Write down the net cell reaction for the purification of impure copper metal. (2)

[11]

Total: 200 marks


NATIONAL SENIOR CERTIFICATE EXAMINATION NOVEMBER 2014

PHYSICAL SCIENCES: PAPER II

EXAMINATION NUMBER

ANSWER SHEET QUESTION 3.5

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER II – DATA SHEET Page i of iii


EXAMINATION DATA SHEET FOR THE PHYSICAL SCIENCES

(CHEMISTRY)

TABLE 1 PHYSICAL CONSTANTS

NAME SYMBOL VALUE

Magnitude of charge on electron e 1,6 10–19

C

Mass of an electron me 9,1 10–31

kg

Standard pressure θp 1,01 510 Pa

Molar gas volume at STP mV 22,4 dm3·mol

–1

Standard temperature θT 273 K

Avogadro's constant NA 6,02 1023 mol

–1

Faraday’s constant F 96 500 C·mol–1

TABLE 2 CHEMISTRY FORMULAE

M

mn

A

Nn

N

m

Vn

V

V

nc OR

mc

MV

Kw [H

3O] [OH] = 1 10

–14 at 298 K

Q = It

Ecell

Ecathode

Eanode

Ecell

Eoxidisingagent

Ereducingagent

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER II – DATA SHEET Page ii of iii


TABLE 3 PERIODIC TABLE

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

1

1 2,1

H

1

Atomic number (Z) 1 2,1

H Electronegativity

2

He

4

2

3 1,0

Li

7

4 1,5

Be

9

1

5 2,0

B

10,8

6 2,5

C

12

7 3,0

N

14

8 3,5

O

16

9 4,0

F

19

10

Ne

20 Relative atomic mass

3

11 0,9

Na

23

12 1,2

Mg

24,3

13 1,5

Aℓ

27

14 1,8

Si

28

15 2,1

P

31

16 2,5

S

32

17 3,0

Cℓ

35,5

18

Ar

40

4

19 0,8

K

39

20 1,0

Ca

40

21 1,3

Sc

45

22 1,5

Ti

48

23 1,6

V

51

24 1,6

Cr

52

25 1,5

Mn

55

26 1,8

Fe

56

27 1,8

Co

59

28 1,8

Ni

59

29 1,9

Cu

63,5

30 1,6

Zn

65,4

31 1,6

Ga

70

32 1,8

Ge

72,6

33 2,0

As

75

34 2,4

Se

79

35 2,8

Br

80

36

Kr 84

5

37 0,8

Rb

85,5

38 1,0

Sr

88

39 1,2

Y

89

40 1,4

Zr

91

41 1,6

Nb

93

42 1,8

Mo

96

43 1,9

Tc

99

44 2,2

Ru

101

45 2,2

Rh

103

46 2,2

Pd

106

47 1,9

Ag

108

48 1,7

Cd

112

49 1,7

In

115

50 1,8

Sn

119

51 1,9

Sb

121

52 2,1

Te

128

53 2,5

I

127

54

Xe

131

6

55

Cs

133

56

Ba

137,3

72

Hf

178,5

73

Ta

181

74

W

184

75

Re

186

76

Os

190

77

Ir

192

78

Pt

195

79

Au

197

80

Hg

200,6

81

Tℓ

204,4

82

Pb

207

83

Bi

209

84

Po

–

85

At

–

86

Rn

–

7

87

Fr

88

Ra

57

La

58

Ce

59

Pr

60

Nd

61

Pm

62

Sm

63

Eu

64

Gd

65

Tb

66

Dy

67

Ho

68

Er

69

Tm

70

Yb

71

Lu

89

Ac

90

Th

91

Pa

92

U

93

Np

94

Pu

95

Am

96

Cm

97

Bk

98

Cf

99

Es

100

Fm

101

Md

102

No

103

Lw

NATIONAL SENIOR CERTIFICATE: PHYSICAL SCIENCES: PAPER II – DATA SHEET Page iii of iii


TABLE 4 STANDARD ELECTRODE POTENTIALS

Half –reaction E°/volt

Incr

easi

ng

red

uci

ng

ab

ilit

y

Incr

easi

ng

ox

idis

ing

ab

ilit

y

Li++e– ⇌ Li – , K++e– ⇌ K – , Cs++e– ⇌ Cs – , Ba ++ e– ⇌ Ba – , Sr ++ e– ⇌ Sr – , Ca ++ e– ⇌ Ca – , Na++e– ⇌ Na – , Mg ++ e– ⇌ Mg – , A ++ e– ⇌ A – , Mn ++ e– ⇌ Mn – , ( O+ e– ⇌ ( g + O(– – , Zn ++ e– ⇌ Zn – , Cr ++ e– ⇌ Cr – , Fe ++ e– ⇌ Fe – , Cd ++ e– ⇌ Cd – , Co ++ e– ⇌ Co – , Ni ++ e– ⇌ Ni – , Sn ++ e– ⇌ Sn – , Pb ++ e– ⇌ Pb – , Fe ++ e– ⇌ Fe – , (++ e– ⇌ ( g , S+ (++ e– ⇌ ( S g + , Sn ++ e– ⇌ Sn + + , SO –+ (++ e– ⇌ SO g + ( O + ,

Cu ++ e– ⇌ Cu + , ( O+O + e– ⇌ O(– + , SO + (++ e– ⇌ S+ ( O + , ) + e– ⇌ )– + , O g + (++ e– ⇌ ( O + , Fe ++e– ⇌ Fe + + , (g ++ e– ⇌ (g + , NO –+ (++e– ⇌ NO g +( O + , Ag++e– ⇌ Ag + , NO –+ (++ e– ⇌ NO g + ( O + , Br + e– ⇌ Br– + , Pt ++ e– ⇌ Pt + , MnO + (++ e– ⇌ Mn ++ ( O + , O + (++ e– ⇌ ( O + , Cr O –+ (++ e– ⇌ Cr ++ ( O + , C g + e– ⇌ C– + , Au ++ e– ⇌ Au + , MnO –+ (++ e– ⇌ Mn ++ ( O + , ( O + (++ e– ⇌ ( O + , F g + e– ⇌ F– + ,

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