DIOCESANCOLLEGE

GRADE 12

PHYSICAL SCIENCE

PAPER 2 - CHEMISTRY

HIGHER GRADE

JUNE 2006

MARKS:200

TIME:2 HOURS

EXAMINER:DL

MODERATOR:GR

General Instructions:

1.Answer ALL the questions.

2.Section A: Follow the instructions.

3Section B: Please start each new Question on a new piece of paper.

4.Calculations: Show your workings.

5.Refer to the attached data sheet where necessary.

Requirements:Pocket calculator

Mathematical instruments

______

QUESTION 1

INSTRUCTIONS

  1. Answer this question on the printed ANSWER SHEET enclosed in your question paper.
  1. Do not make any other marks on your answer sheet. Any calculations or writing that may be necessary when answering multiple-choice questions 1.1 to 1.15 should be done on blank / scrap paper.
  1. ATTACH THE COMPLETED ANSWER SHEET TO THE FRONT OF YOUR ANSWER SCRIPT.

DON’T FORGET TO PUT YOUR NAME ON IT!

  1. Four possible answers, indicated by A, B, C and D are supplied with each question. Choose only that answer which in your opinion is the correct or best one and mark the appropriate block on your answer sheet with a cross (X).

If more than one block is marked, no marks will be awarded for that answer.

Example

QUESTION:The generally accepted value of the melting point of ice is ……..

A0 K

B00 C

C100 K

D1000 C

ANSWER

A / B / C / D

Section A multiple choice questions: Answer all the questions on the answer sheet provided by making a cross in the box corresponding to the correct answer.

1.1The unusually high boiling point of water in relation to the boiling points of the

other group 6 hydrides is generally ascribed to the phenomenon of………..

a)molecular mass.

b)atomic number.

c)hydrogen bonding.

d)polar covalent bonding.

1.2When an oil spill occurs at sea, one of the ways in which it is combated is by spraying non polar solvents onto the spill. This works because………

a)oil dissolves in water and the non-polar solvent stops this.

b)oil dissolves in the non polar solvent and can be dispersed.

c)oil and water are miscible and need an agent to assist.

d)oil is a polar solute.

1.3The forces which hold the molecules together in solid CO2 are……….

a)hydrogen bonds.

b)van der Waals forces.

c)ionic bonds.

d)covalent bonds.

1.4A standard solution is made up of potassium chloride in water containing a concentration of potassium ions of 0,2 mol.dm-3. If 20 cm3 of this solution is added to 80 cm3 of distilled water, then the concentration of potassium ions in mol.dm-3 in the new solution will be……..

a)0,01

b)0,02

c)0,03

d)0,04

1.5Which of the following statement/s concerning real gases is/arecorrect?

1)there exist forces of attraction between the molecules.

2)the collisions between the gas molecules are perfectly elastic.

3)the molecules of the gas occupy no volume.

a)1

b)1 and 2

c)2 and 3

d)3

1.6The Kelvin temperature scale is defined in terms of the…………

a)melting point of ice.

b)potential energy of molecules.

c)kinetic energy of molecules.

d)boiling point of liquid nitrogen.

1.7Which one of the following graphs best represents the deviation of a real gas from ideal behaviour according to Boyle’s Law?

PPPP

V V V V

a) b) c) d)

1.8One of the more common uses for the sulphate salts is…..

a)in the preparation fertilizers.

b)the production of photographic plates.

c)the production of explosives.

d)as a lubricant.

1.9The process by which Nitric acid is produced is known as………..

a)sintered glass filtration.

b)the Ostwald process.

c)acid base reactions.

d)the Haber process.

1.10In the purification of water, Cl2 reacts with water in order to produce…………which decomposes in sunlight.

a)HOCl

b)CaCl2

c)HCl

d)Ca(OH)2

1.11A test for sulphur dioxide gas is…………….

a)filter paper soaked in lead acetate turns black.

b)moistened filter paper turns blue.

c)filter paper soaked in KMnO4 solution decolourises.

d)moistened litmus paper turns blue.

1.12The rate of a reaction can be determined by……………..

a)the rate of change of the catalyst.

b)the rate of loss of mass of reactants.

c)the rate of loss of mass of products.

d)the rate of gain of mass of the reactants

1.13An increase in the temperature of a reaction will always……………

a)decrease the rate of a reaction.

b)result in the formation of more products.

c)increase the rate of a reaction.

d)have no effect on the rate of reaction.

1.14What effect will the addition of a catalyst at constant temperature have on the amount of products produced for a given reaction?

a)No effect at all.

b)Increase.

c)Decrease

d)Insufficient information to decide.

1.15When the concentration of a product is increased in a reaction mixture at equilibrium, which of the following will be the immediate result?

a)The right hand side of the reaction will be slowed down.

b)The rate of the reverse reaction will be increased.

c)The rate of the forward reaction will be increased.

d)The left hand side of the reaction will be speeded up.

Total 15 x 4 [60]

Section B Long questions. Answer this section on the lined paper provided. The information pamphlet provided may be of use to you in this section.

Question Two:

2.1The following compounds are listed from 1 to 5 below. Identify what type of lattice structure it would be, (molecular, covalent, ionic, metallic) and what the inter-particle force is that holds it together as a solid.

Compound / Type of solid / I/particle force
1.Iodine / A / F
2.Water / B / G
3.Diamond / C / H
4.Aluminium / D / I
5.Sodium fluoride / E / J

Write the letter only and the word/s corresponding to the correct answer on your script. (10)

2.2The grease stains in a shirt are readily removed using ether (a non polar organic compound) soaked in cotton wool.

2.2.1Explain in terms of your understanding of the dissolution process and inter-molecular forces why ether is effective for grease stains but water is not. (4)

2.2.2What specific type of intermolecular force is responsible for sodium chloride dissolving in water? (2)

2.3A solution of sodium carbonate in water is a very good mild alkaline solution often used to provide some relief for a bee- sting or other minor acid type burns.

2.3.1Calculate the mass of anhydrous sodium carbonate (Na2CO3) required to produce 800 cm3 of a solution of concentration 0,025 mol.dm-3 in water. (4)

2.3.2What is the concentration of sodium ions in this solution?(2)

2.3.3What mass of NaOH in the same volume of water (800 cm3) would produce the same concentration of sodium ions? (4)

/26/

Question Three:

3.1The Kelvin Temperature scale is derived from the relationship between pressure and temperature as shown in the following graph. The graph is derived from experimental results obtained over a certain temperature range while investigating the relationship between Pressure and Temperature.

3.1.1Why is there a section of the straight line which is dotted?

(The section at very low temperature and pressure)(2)

3.1.2At what value in 0C would the dotted line of the graph cut the x-axis?(2)

3.1.3What is this value of temperature known as?(2)

3.2An ideal gas does not exist in reality but some gases approximate ideal gas behaviour.

3.2.1Give any two properties of an ideal gas.(2)

3.2.2Draw a sketch graph showing the relationship between the volume of a given mass of gas and its temperature. (3)

3.2.3On the graph show how the behaviour of a real gas would deviate at low temperatures. (1)

3.3A sample of ammonia gas (NH3) is found to exert a pressure of 30 kPa at a temperature of 100K when contained in a 2 dm3 flask.

3.3.1Calculate the mass of ammonia gas that this represents.(6)

3.3.2There is actually a little more than this amount of gas in the flask. Explain why the pressure is less than expected for this amount of real gas. (4)

3.4A weather balloon is filled at sea-level (pressure of 100 kPa) at a temperature of 250 C to a volume of 2 m3. It is found to have a volume of 4,2 m3 at an altitude of 12 000 m where the temperature is a cool -370 C. Calculate the pressure of the gas in the balloon at this altitude. (5)

/27/

Question Four:

4.1The production of nitric acid is an important industrial process. In it, NH3 is oxidised through NO to NO2 and then reacted with water to produce HNO3.

4.1.1What is the catalyst used in the first step of this process?(2)

4.1.2Give the balanced chemical reaction for the last step in this process.(3)

4.1.3Give two major uses for nitric acid.(2)

4.1.4Give a balanced chemical reaction for the preparation of ammonium nitrate. (3)

4.1.5Name the reddish brown gas produced when HNO3(conc.) is added to Cu

metal.(2)

4.2One of the properties of SO2 and H2S which we demonstrate is their reducing actions.

4.2.1What is the colour change which is observed when H2S is bubbled through an acidified solution of K2Cr2O7 ? (2)

4.2.2What is the precipitate which forms in this reaction?(2)

4.2.3Write down the oxidation half reaction for this reaction from table 4b.(2)

4.2.4Write down the reduction half reaction for this reaction from table 4b.(2)

4.2.5Give the overall balanced redox reaction for the reaction of H2Sand K2Cr2O7. (2)

4.3The production of sulphuric acid in industry is commonly known as the Contact Process.

It involves the reaction between SO2 and O2under specific catalysis.

4.3.1Why is it known as the Contact process?(2)

4.3.2What is the product of the reaction between these two substances?(2)

4.3.3One of the uses of sulphuric acid is in the production of sulphates. Give a balanced chemical equation for the preparation of calcium sulphate from calcium hydroxide, Ca(OH)2. (3)

4.3.4There are two common ways of showing the dehydrating action of concentrated sulphuric acid. Describe one of them. (4)

4.3.5The laboratory preparation of SO2 is accomplished by the reaction of an acid on a salt. Write down the balanced equation for this reaction. (3)

4.3.6In the reaction between H2S and SO2, sulphur and water are produced. Which of H2Sand SO2 is the oxidizing agent and which is the reducing agent? (4)

4.4In the manufacture of paper, wood is turned into pulp and then bleached before being rolled out into sheets and then subsequently treated to manufacture different types of paper.

4.4.1Explain why chlorine is a useful bleaching agent.(2)

4.4.2How is chlorine obtained in industry?(2)

4.4.3What is the danger of using chlorine gas in industry?(3)

4.4.4Given a solution which may contain bromide ions. Describe a simple test to confirm that these are indeed bromide ions. (4)

/51/

Question Five:

5.1The chemical industry relies heavily on the understanding of and manipulation of the factors affecting the rates of reactions, particularly in the manufacturing industry.

5.1.1Name the four factors which affect the rate of a reaction other than the nature of the reacting substances and say how each factor can be used to increase the rate of a given reaction (8)

5.1.2State Le Chatelier’s principle.(3)

5.1.3Draw a sketch graph showing the initial rates of both the forward and reverse reactions for the overall reaction until it reaches equilibrium;

A(g) + 2B(g) ⇌ AB2(g)

On the graph indicate the time when equilibrium is achieved in the reaction.(5)

5.2In the reaction between CO and steam to form CO2 and CH4 the chemical equation describing the reaction is as follows;

2CO(g) + 4 H2O(g) ⇌ 2CH4(g) + 3O2(g) ∆H < 0

5.2.1Is this reaction exothermic or endothermic?(1)

5.2.2Would the amount of CH4 be greater at a higher or a lower temperature? Explain.(3)

5.2.3The engineer on the plant asks if he should install high pressure vessels to improve the yield. What is your answer to him and why? (3)

5.2.4What other possible method could you use to increase the amount of methane and oxygen produced? Explain how this works. (3)

5.2.5Your accountant suggests using a catalyst to improve the yield. What is your explanation to him? (3)

5.3The equilibrium concentrations of both NO2(dark reddish-brown gas) and N2O4(pale yellow gas)can be manipulated in a closed flask by both pressure and temperature. The reaction is

2NO2(g) ⇌ N2O4(g) ∆H < 0

5.3.1When the flask is placed in hot water what colour will the contents become?(1)

5.3.2Why does this colour change occur?(2)

5.3.3If the pressure is increased on the contents at a constant temperature, what

colour will the contents of the flask bewhen equilibrium is re-established?(1)

5.3.4Explain this colour change in terms of Le Chatelier’s principle.(3)

/36/

Total [200]

DATA FOR PHYSICAL SCIENCE

PAPER 2 (CHEMISTRY)

TABLE 1 : PHYSICAL CONSTANTS

Avogadro’s constant / NA or L / 6,02 x 1023 mol-1
Molar gas constant / R / 8,31 J.K-1.mol-1
Standard pressure / p / 1,013 x 105 Pa
Molar gas volume at STP / Vm / 22,4 dm3.mol-1
Standard temperature / T / 273 K

TABLE 2 : FORMULAE





/
at 298 K

Ecell = Eoxidising agent - Ereducing agent
Ecell = Ecathode - Eanode

- 1 -

TABLE 3 : THE PERIODIC TABLE OF ELEMENTS

I / KEY / 0
2,1 / 1
H
1 / II /

Atomic number

/ III / IV / V / VI / VII / 2
He
4
1,0 / 3
Li
7 / 1,5 / 4
Be
9 / Electronegativity / 1,9 / 29
Cu
63,5 / Symbol / 2,0 / 5
B
11 / 2,5 / 6
C
12 / 3,0 / 7
N
14 / 3,5 / 8
O
16 / 4,0 / 9
F
19 / 10
Ne
20
0,9 / 11
Na
23 / 1,2 / 12
Mg
24 / Relative atomic mass (approximately) / 1,5 / 13
Aℓ
27 / 1,8 / 14
Si
28 / 2,1 / 15
P
31 / 2,5 / 16
S
32 / 3,0 / 17
Cℓ
35,5 / 18
Ar
40
0,8 / 19
K
39 / 1,0 / 20
Ca
40 / 1,3 / 21
Sc
45 / 1,5 / 22
Ti
48 / 1,6 / 23
V
51 / 1,6 / 24
Cr
52 / 1,5 / 25
Mn
55 / 1,8 / 26
Fe
56 / 1,8 / 27
Co
59 / 1,8 / 28
Ni
59 / 1,9 / 29
Cu
63,5 / 1,6 / 30
Zn
65 / 1,6 / 31
Ga
70 / 1,8 / 32
Ge
73 / 2,0 / 33
As
75 / 2,4 / 34
Se
79 / 2,8 / 35
Br
80 / 36
Kr
84
0,8 / 37
Rb
86 / 1,0 / 38
Sr
88 / 1,2 / 39
Y
89 / 1,4 / 40
Zr
91 / 41
Nb
92 / 1,8 / 42
Mo
96 / 1,9 / 43
Tc / 2,2 / 44
Ru
101 / 2,2 / 45
Rh
103 / 2,2 / 46
Pd
106 / 1,9 / 47
Ag
108 / 1,7 / 48
Cd
112 / 1,7 / 49
In
115 / 1,8 / 50
Sn
119 / 1,9 / 51
Sb
122 / 2,1 / 52
Te
128 / 2,5 / 53
I
127 / 54
Xe
131
0,7 / 55
Cs
133 / 0,9 / 56
Ba
137 / 57
La
139 / 1,6 / 72
Hf
179 / 73
Ta
181 / 74
W
184 / 75
Re
186 / 76
Os
190 / 77
Ir
192 / 78
Pt
195 / 79
Au
197 / 80
Hg
201 / 1,8 / 81
Tℓ
204 / 1,8 / 82
Pb
207 / 1,9 / 83
Bi
209 / 2,0 / 84
Po / 2,5 / 85
At / 86
Rn
0,7 / 87
Fr / 0,9 / 88
Ra
226 / 89
Ac
58
Ce
140 / 59
Pr
141 / 60
Nd
144 / 61
Pm / 62
Sm
150 / 63
Eu
152 / 64
Gd
157 / 65
Tb
159 / 66
Dy
163 / 67
Ho
165 / 68
Er
167 / 69
Tm
169 / 70
Yb
173 / 71
Lu
175
90
Th
232 / 91
Pa / 92
U
238 / 93
Np / 94
Pu / 95
Am / 96
Cm / 97
Bk / 98
Cf / 99
Es / 100
Fm / 101
Md / 102
No / 103
Lr

- 1 -

TABLE 4A: STANDARD ELECTRODE POTENTIALS

Half-reaction / E° /volt
/ F2 / + / 2e- / ⇌ / 2F- / +2,87
H2O2 + 2H+ / + / 2e- / ⇌ / 2H2O / +1,77
MnO4- + 8H+ / + / 5e- / ⇌ / Mn2+ + 4H2O / +1,51
Au3+ / + / 3e- / ⇌ / Au / +1,42
Cℓ2 / + / 2e- / ⇌ / 2Cℓ- / +1,36
Cr2O72- + 14H+ / + / 6e- / ⇌ / 2Cr3+ + 7H2O / +1,33
O2 + 4H+ / + / 4e- / ⇌ / 2 H2O / +1,23
MnO2 + 4H+ / + / 2e- / ⇌ / Mn2+ + 2H2O / +1,21
Pt2+ / + / 2e- / ⇌ / Pt / +1,20
Br2 / + / 2e- / ⇌ / 2Br- / +1,09
NO3- + 4H+ / + / 3e- / ⇌ / NO + 2H2O / +0,96
/ Ag+ / + / e- / ⇌ / Ag / +0,80
NO3- + 2H+ / + / e- / ⇌ / NO2 + H2O / +0,80
Hg2+ / + / 2e- / ⇌ / Hg / +0,79
Fe3+ / + / e- / ⇌ / Fe2+ / +0,77
O2 + 2H+ / + / 2e- / ⇌ / H2O2 / +0,68
I2 / + / 2e- / ⇌ / 2I- / +0,54
SO2 + 4H+ / + / 4e- / ⇌ / S + 2H2O / +0,45
2H2O + O2 / + / 4e- / ⇌ / 4OH- / +0,40
Cu2+ / + / 2e- / ⇌ / Cu / +0,34
SO42- + 4H+ / + / 2e- / ⇌ / SO2 + 2H2O / +0,17
Cu2+ / + / e- / ⇌ / Cu+ / +0,16
Sn4+ / + / 2e- / ⇌ / Sn2+ / +0,15
S + 2H+ / + / 2e- / ⇌ / H2S / +0,14
2H+ / + / 2e- / ⇌ / H2 / 0,00
Fe3+ / + / 3e- / ⇌ / Fe / -0,04
Pb2+ / + / 2e- / ⇌ / Pb / -0,13
Sn2+ / + / 2e- / ⇌ / Sn / -0,14
Ni2+ / + / 2e- / ⇌ / Ni / -0,25
Co2+ / + / 2e- / ⇌ / Co / -0,28
Cd2+ / + / 2e- / ⇌ / Cd / -0,40
Fe2+ / + / 2e- / ⇌ / Fe / -0,44
Cr3+ / + / 3e- / ⇌ / Cr / -0,74
Zn2+ / + / 2e- / ⇌ / Zn / -0,76
2H2O / + / 2e- / ⇌ / H2 + 2OH- / -0,83
Mn2+ / + / 2e- / ⇌ / Mn / -1,18
Aℓ3+ / + / 3e- / ⇌ / Aℓ / -1,66
Mg2+ / + / 2e- / ⇌ / Mg / -2,37
Na+ / + / e- / ⇌ / Na / -2,71
Ca2+ / + / 2e- / ⇌ / Ca / -2,87
Sr2+ / + / 2e- / ⇌ / Sr / -2,89
Ba2+ / + / 2e- / ⇌ / Ba / -2,90
Cs+ / + / e- / ⇌ / Cs / -2,92
K+ / + / e- / ⇌ / K / -2,93
Li+ / + / e- / ⇌ / Li / -3,05

TABLE 4B: STANDARD ELECTRODE POTENTIALS

Half-reaction / E° /volt
/ Li+ / + / e- / ⇌ / Li / -3,05
K+ / + / e- / ⇌ / K / -2,93
Cs+ / + / e- / ⇌ / Cs / -2,92
Ba2+ / + / 2e- / ⇌ / Ba / -2,90
Sr2+ / + / 2e- / ⇌ / Sr / -2,89
Ca2+ / + / 2e- / ⇌ / Ca / -2,87
Na+ / + / e- / ⇌ / Na / -2,71
Mg2+ / + / 2e- / ⇌ / Mg / -2,37
Aℓ3+ / + / 3e- / ⇌ / Aℓ / -1,66
Mn2+ / + / 2e- / ⇌ / Mn / -1,18
2H2O / + / 2e- / ⇌ / H2 + 2OH- / -0,83
/ Zn2+ / + / 2e- / ⇌ / Zn / -0,76
Cr3+ / + / 3e- / ⇌ / Cr / -0,74
Fe2+ / + / 2e- / ⇌ / Fe / -0,44
Cd2+ / + / 2e- / ⇌ / Cd / -0,40
Co2+ / + / 2e- / ⇌ / Co / -0,28
Ni2+ / + / 2e- / ⇌ / Ni / -0,25
Sn2+ / + / 2e- / ⇌ / Sn / -0,14
Pb2+ / + / 2e- / ⇌ / Pb / -0,13
Fe3+ / + / 3e- / ⇌ / Fe / -0,04
2H+ / + / 2e- / ⇌ / H2 / 0,00
S + 2H+ / + / 2e- / ⇌ / H2S / +0,14
Sn4+ / + / 2e- / ⇌ / Sn2+ / +0,15
Cu2+ / + / e- / ⇌ / Cu+ / +0,16
SO42- + 4H+ / + / 2e- / ⇌ / SO2 + 2H2O / +0,17
Cu2+ / + / 2e- / ⇌ / Cu / +0,34
2H2O + O2 / + / 4e- / ⇌ / 4OH- / +0,40
SO2 + 4H+ / + / 4e- / ⇌ / S + 2H2O / +0,45
I2 / + / 2e- / ⇌ / 2I- / +0,54
O2 + 2H+ / + / 2e- / ⇌ / H2O2 / +0,68
Fe3+ / + / e- / ⇌ / Fe2+ / +0,77
Hg2+ / + / 2e- / ⇌ / Hg / +0,79
NO3- + 2H+ / + / e- / ⇌ / NO2 + H2O / +0,80
Ag+ / + / e- / ⇌ / Ag / +0,80
NO3- + 4H+ / + / 3e- / ⇌ / NO + 2H2O / +0,96
Br2 / + / 2e- / ⇌ / 2Br- / +1,09
Pt2+ / + / 2e- / ⇌ / Pt / +1,20
MnO2 + 4H+ / + / 2e- / ⇌ / Mn2+ + 2H2O / +1,21
O2 + 4H+ / + / 4e- / ⇌ / 2 H2O / +1,23
Cr2O72- + 14H+ / + / 6e- / ⇌ / 2Cr3+ + 7H2O / +1,33
Cℓ2 / + / 2e- / ⇌ / 2Cℓ- / +1,36
Au3+ / + / 3e- / ⇌ / Au / +1,42
MnO4- + 8H+ / + / 5e- / ⇌ / Mn2+ + 4H2O / +1,51
H2O2 + 2H+ / + / 2e- / ⇌ / 2H2O / +1,77
F2 / + / 2e- / ⇌ / 2F- / +2,87

- 1 -

ANSWER SHEET

1.1 / A / B / C / D
1.2 / A / B / C / D
1.3 / A / B / C / D
1.4 / A / B / C / D
1.5 / A / B / C / D
1.6 / A / B / C / D
1.7 / A / B / C / D
1.8 / A / B / C / D
1.9 / A / B / C / D
1.10 / A / B / C / D
1.11 / A / B / C / D
1.12 / A / B / C / D
1.13 / A / B / C / D
1.14 / A / B / C / D
1.15 / A / B / C / D

- 1 -