Physical Science Mock Exam

Physical Science Mock Exam

PAPER 2 - CHEMISTRY

September 2015

Examiner: A. Stevens

/ /

MARKS: 150

TIME: 3hours

Moderator: G Robertson

Thisquestionpaperconsistsof12pages of questions and4data sheets.

INSTRUCTIONS AND INFORMATION

1. Write your examination number in the appropriate spaces on the ANSWER BOOK.
2. This question paper consists of NINE questions. Answer ALL the questions in the ANSWER BOOK.
3. Start EACH question on a NEW page in the ANSWER BOOK.
4. Number the answers correctly according to the numbering system used in this question paper.
5. Leave ONE line between two subquestions, for example between QUESTION 2.1 and QUESTION 2.2.
6. You may use a non-programmable calculator.
7. You may use appropriate mathematical instruments.
8. You are advised to use the attached DATA SHEETS.
9. Show ALL formulae and substitutions in ALL calculations.
10. Round off your final numerical answers to a minimum of TWO decimal places.
11. Give brief motivations, discussions, et cetera where required.
12. Write neatly and legibly.

QUESTION 1: MULTIPLE CHOICE QUESTIONS

Four options are provided as possible answers to the following questions. Each question has only ONE correct answer. Write only the letter (A–D) next to the question number (1.1–1.10) in the ANSWER BOOK, for example 1.11. D.

1.1Which of the following molecules is a positional isomer of hex-2-ene?

A. / / B. /
C. / / D. /

1.2Which is the correct name for the molecule below?

A. / butyl ethanoate
B. / ethyl propanoate
C. / propyl ethanoate
D. / ethyl butanoate

1.3Which of the following aqueous reactions will produce an alkaline solution?

A. / NH3 + CH3COOH
B. / Ca(OH)2 + HNO3
C. / NaOH + CH3COOH
D. / Na2CO3 + HNO3

1.4Which solution will turn red litmus to blue?

A. / HCl(aq)
B. / NaCl(aq)
C. / CH3OH(aq)
D. / NaOH(aq)

1.5The graph below represents the fraction of particles against the kinetic energy for an identical sample of reacting particles at two different temperatures, T1 and T2. How will the diagram change if the activation energy is increased?

A. / Both curves T1 and T2 would shift upwards.
B. / Area Y will increase.
C. / The curves will become flatter and shift left.
D. / Areas X and Y will decrease.

1.6Consider the following equilibrium:

H2(g) + I2(g) + energy ⇋ 2HI(g)

Which graph shows what happens when some HI is removed and a new equilibrium is established?

A. / B. / C. / D.

1.7Which ONE of the following will reduce Pb2+ toPb, but notFe2+to Fe?

A. / Copper
B. / Nickel
C. / Mercury
D. / Hydrogen

1.8What is the effect of adding vanadium pentoxide to the following equilibrium?

2SO2(g) + O2 (g) ⇋ 2 SO3(g)

Activation Energy / Yield of sulphur trioxide at equilibrium
A. / Decrease / Unchanged
B. / Decrease / Increase
C. / Increase / Unchanged
D. / Increase / Increase

1.9In the electrolysis of aqueous sodium sulphate which ONE of the following statements is TRUE?

A. / Sulphate ions react at the anode
B. / Sodium is formed at the cathode.
C. / Oxidation takes place at the anode.
D. / Electrons are gained at the anode.

1.10A diagram of a membrane cell used in the chlor-alkali industry is shown below. X and Y represent the two electrodes and the products of the process are A, B, and C.

Product B / ProductC
A. / H2 / Cl2
B. / NaOH / H2
C. / NaOH / Cl2
D. / Cl2 / H2

10 x 2 = [20]

QUESTION 2:

Consider the organic compounds A – H shown in the table below

A / C16H30 / B / but-2-ene
C / / D /
E / / F / CH3CH2CHO
G / / H /

2.1Give the name of the family of compounds of which the following are members:

2.1.1Compound A(1)

2.1.2Compound E(1)

2.2Give the IUPAC names for:

2.2.1Compound C(3)

2.2.2Compound G(2)

2.3Write down:

2.3.1The name of the functional group in compound F.(1)

2.3.2The type of alcohol in compound D. Write only PRIMARY, SECONDARY or
TERTIARY.(1)

2.4Draw:

2.4.1The repeat unit for the addition polymer of compound B.(2)

2.4.2The structural formula for a chain isomer of compound H.(2)

[13]

QUESTION 3:

Examine the graph below and answer the questions that follow.

3.1Define the term ‘boiling point’.(2)

3.2Explain, by referring to the functional groups present, why the curve for the carboxylic
acids is higher than that for the esters.(4)

3.3Draw a sketch graph (no values) showing what you would expect the curves to look like
if vapour pressure replaced boiling point in the analysis.(2)

[8]

QUESTION 4:

4.1One of the most used polymers polyethylene terephthalate, or PET, has the structure shown below. The annual worldwide production of PET is about 40 million tonnes and is growing at 7% per year.

4.1.1What type of polymer is PET? Write only ADDITION or CONDENSATION.(1)

4.1.2Define the term ‘monomer’.(2)

4.1.3Give the formulae of the PET acid monomer.(2)

4.2The following reaction of pentane takes place in a university laboratory:

CH3CH2CH2CH2CH3 → CH2BrCH2CH2CH2CH3

4.2.1What reagent and conditions are required in order to achieve this reaction?(2)

4.2.2The above reaction seldom gives a single product. Write down the condensed formula of another possible organic product. (2)

4.2.3The organic chemist performing this reaction had to crack a wax sample that he
had, C32H66,to produce the pentane. Using molecular formulae, write a possible balanced equationfor the cracking of the wax to give this product. (3)

4.3In the flow diagram below, butan-2-ol is being used as the starting material for 2 reactions:

4.3.1Write down the reactant(s) and conditions needed to perform Reaction 1.(2)

4.3.2Draw the structural formula of Compound A.(2)

4.3.3Given that compound B is an alkane, write down the complete conditions
required to complete reaction 3.(3)

4.3.4What type of addition reaction is Reaction 3?(1)

[20]

QUESTION 5:

The graphs below show the rate of evolution of nitrogen gas when a constant mass of ammonium chloride solid is added to a constant volume of solution of sodium nitritesolution. Three of the five sets of conditions have been shown in the table:

NH4Cl(s) + NaNO2(aq) → N2(g) + NaCl(aq) + 2H2O(l)

Exp / Temp
(ᵒC) / NH4Cl / [NaNO2] (mol.dm-3)
1 / 35 / Powder / 0.50
2 / 25 / Lumps / 0.25
3 / 35 / Powder / 0.25

5.1Define the term ‘reaction rate’.(2)

5.2Assign curves A, C and E to the correct set of conditions (ie assign which curve
corresponds to experiments 1,2 and 3).(2)

5.3Write down a likely set of conditions for curve B.(3)

5.4Applying Collision Theory, explain the difference in the shape of lines A and C.(4)

5.5What is the limiting reactant in this reaction? (1)

5.6How would you expect the rate of reaction to change if an aqueous solution of
NH4Cl was used? Write only INCREASE, DECREASE or NO CHANGE.(1)

5.7If ‘M’on the graph corresponds to 200cm3 Nitrogen at STP and 0.500g ammonium
chloride was used in the experiment, calculate the percentage yield ofnitrogen. (6)

[19]

QUESTION 6:

Nitrosyl bromide (NOBr) is a red gas that is frequently used in studies of reactionrates. The decomposition of NOBris brought about by exposing it to light. The reaction takes place according to the reaction:

2NOBr(g) 2NO(g) + Br2(g)

Some NOBr was placed 2.00 dm3flask that was connected to another flask of the same volume via a closed glass tap as shown below. The system was placed in sunlight and heated to 100ᵒC. Once it had reached equilibrium Kcwas established to be 0.0143.

6.1What is meant by chemical equilibrium?(2)

6.2If the equilibrium concentration of Br2 was 0.34mol.dm-3,calculate the number moles
ofNOBrthat wereinitially placed in the container.(8)

6.3The gas tap between the two flasks was then opened.

6.3.1What was the effect on the amount of Br2 at equilibrium? Write only INCREASE,
DECREASE or NO CHANGE.(1)

6.3.2Explain your answer to 6.3.1.(4)

6.4When the flasks containing the equilibrium mixture were heated to 130ᵒC at time t1, the
rates graph changed as shown below.

Is the forward reaction ENDOTHERMIC or EXOTHERMIC?(1)

[16]

QUESTION 7:

Once a bottle of wine is opened and the air gets in it starts to go off. The wine gets more acidic as the ethanol is oxidized to ethanoic acid (acetic acid) by acetic acid bacteria (called Acetobacter). This is fine if you want to make wine vinegar but not if you want the wine to be drinkable.

A student is investigating the rate of oxidation by the bacteria. He performs a titration of the wine with sodium hydroxide every 12 hours to determine the acid content.

7.1Write a hypothesis for this investigation.(1)

7.2Name the independent variable.(1)

7.3Write down twoappropriate fixed variables.(2)

7.4Suggest a suitable indicator for this titration.(1)

7.5A standard solution of sodium hydroxide is prepared by dissolving 0.27g in water and making the solution up to 2.00dm3. Calculate the pH of this solution. (7)

7.6All wine also contains a diprotic acid called tartaric acid that must be taken into consideration.

7.6.1What is meant by the term ‘diprotic’(1)

7.6.2How would the pH of a 0.5 mol.dm-3 solution of sulphuric acid compare to that
of atartaric acid solution with the same concentration?
Write only HIGHER, LOWER or THE SAME.(1)

7.6.3The following equilibrium occurs in aqueous tartaric acid:

Write down the letter of a species in the equation that is:

7.6.3.1The conjugate base of species D, H3O+.(1)

7.6.3.2An organic ampholyte.(1)

7.7A sample of the wine from a freshly opened bottle was titrated against a standard sodium hydroxide solution with a concentration of 2.50 x 10-3 mol.dm-3. A volume of 25cm3 of the wine required 4.05 cm3sodium hydroxide to reach the endpoint. After 5 days the titration was repeated and a titre of 16.35 cm3 of sodium hydroxide was recorded. Assuming that the tartaric acid concentration is constant, calculate the concentration of ethanoic acid in the wine on day 5.

CH3COOH + NaOH → CH3COONa + H2O

(5)

7.8Why is this analysis not suitable for red wine?(1)

[22]

QUESTION 8:

8.1A galvanic cell containing an unknown metal electrode Mis represented in the diagram below. The initial reading on the voltmeter is 1.39 V. The cell operates under standard conditions.

8.1.1Give the definition for a reducing agent(2)

8.1.2Use standard electrode potentials to determine the identity of metal M.(4)

8.1.3Write the complete cell notation for this cell.(3)

8.1.4What is the function of the salt bridge?(2)

8.1.5In which direction will CATIONS move in the salt bridge?(1)

8.1.6How would the potential of the cell be affected if a higher concentration of Al3+
was used? Write only INCREASE, DECREASE or STAYS THE SAME.(1)

8.2Examine the electrolytic cell below and answer the questions that follow:

8.2.1What is observed at the cathode?(1)

8.2.2Write down the half - reaction taking place at electrode B.(1)

8.2.3Give the overall cell reaction.(3)

8.2.4Name the process whereby the reduction reaction in this cell is put to a
practical use. (1)

[19]

QUESTION 9:

The schematic diagram below lays out the process involved in the production of two fertilisers.

9.1The production of ammonia itself was optimised in the late 1920’s by reacting nitrogen with hydrogen.

9.1.1How is nitrogen for the industry obtained.(1)

9.1.2The production of ammonia is increased if extremely high pressures are used.

Why is a pressure greater than 300 atmospheres not usually used?(2)

9.2Write the name of GAS A.(1)

9.3Name the process for producing ACID B from ammonia.(1)

9.4Write a balanced equation for the conversion of ACID Bto FERTILIZER G.(2)

9.5Write down the name of LIQUID D.(1)

9.6A 20 kg bag containing a commercial fertiliser mix for roses has the number 10:12:6 (25)
printed on it.

9.6.1What is the meaning of this ratio?(1)

9.6.2Why is the presence of potassium beneficial for plant growth?(1)

9.6.3Calculate the mass of potassium present in the bag.(3)

[13]

TOTAL = 150

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DATA FOR PHYSICAL SCIENCES GRADE 12

PAPER 2 (CHEMISTRY)

TABLE 1: PHYSICAL CONSTANTS/TABEL 1: FISIESE KONSTANTES

NAME/NAAM / SYMBOL/SIMBOOL / VALUE/WAARDE
Standard pressure
Standaarddruk / / 1,013 x 105 Pa
Molar gas volume at STP
Molêregasvolume by STD / Vm / 22,4 dm3∙mol-1
Standard temperature
Standaardtemperatuur / / 273 K
Charge on electron
Lading of electron / E / -1.6 x 10-19 C
Avogadro’s number / NA / 6,023 x 1023 mol-1

TABLE 2: FORMULAE/TABEL 2: FORMULES

/ or / or
/ pH = - log[H3O+] / Kw = [H3O+][OH-] at 298 K
q = It
W = Vq / /
/
/

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TABLE 3: THE PERIODIC TABLE OF ELEMENTS

1
(I) / 2
(II) / 3 / 4 / 5 / 6 / 7 / 8 / 9 / 10 / 11 / 12 / 13
(III) / 14
(IV) / 15
(V) / 16
(VI) / 17
(VII) / 18
(VIII)
2,1 / 1
H
1 / 2
He
4
1,0 / 3
Li
7 / 1,5 / 4
Be
9 / 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 / / 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

TABEL 3: DIE PERIODIEKE TABEL VAN ELEMENTE

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TABLE 4A: STANDARD REDUCTION POTENTIALS

TABEL 4A: STANDAARD REDUKSIEPOTENSIALE

Half-reactions/Halfreaksies / (V)
F2(g) + 2e / ⇌ / 2F / + 2,87
Co3+ + e / ⇌ / Co2+ / + 1,81
H2O2 + 2H+ +2e / ⇌ / 2H2O / +1,77
MnO + 8H+ + 5e / ⇌ / Mn2+ + 4H2O / + 1,51
Cℓ2(g) + 2e / ⇌ / 2Cℓ / + 1,36
Cr2O + 14H+ + 6e / ⇌ / 2Cr3+ + 7H2O / + 1,33
O2(g) + 4H+ + 4e / ⇌ / 2H2O / + 1,23
MnO2+ 4H+ + 2e / ⇌ / Mn2+ + 2H2O / + 1,23
Pt2+ + 2e / ⇌ / Pt / + 1,20
Br2(ℓ) + 2e / ⇌ / 2Br / + 1,07
NO + 4H+ + 3e / ⇌ / NO(g) + 2H2O / + 0,96
Hg2+ + 2e / ⇌ / Hg(ℓ) / + 0,85
Ag+ + e / ⇌ / Ag / + 0,80
NO + 2H+ + e / ⇌ / NO2(g) + H2O / + 0,80
Fe3+ + e / ⇌ / Fe2+ / + 0,77
O2(g) + 2H+ + 2e / ⇌ / H2O2 / + 0,68
I2 + 2e / ⇌ / 2I / + 0,54
Cu+ + e / ⇌ / Cu / + 0,52
SO2 + 4H+ + 4e / ⇌ / S + 2H2O / + 0,45
2H2O + O2 + 4e / ⇌ / 4OH / + 0,40
Cu2+ + 2e / ⇌ / Cu / + 0,34
SO + 4H+ + 2e / ⇌ / SO2(g) + 2H2O / + 0,17
Cu2+ + e / ⇌ / Cu+ / + 0,16
Sn4+ + 2e / ⇌ / Sn2+ / + 0,15
S + 2H+ + 2e / ⇌ / H2S(g) / + 0,14
2H+ + 2e / ⇌ / H2(g) / 0,00
Fe3+ + 3e / ⇌ / Fe /  0,06
Pb2+ + 2e / ⇌ / Pb /  0,13
Sn2+ + 2e / ⇌ / Sn /  0,14
Ni2+ + 2e / ⇌ / Ni /  0,27
Co2+ + 2e / ⇌ / Co /  0,28
Cd2+ + 2e / ⇌ / Cd /  0,40
Cr3+ + e / ⇌ / Cr2+ /  0,41
Fe2+ + 2e / ⇌ / Fe /  0,44
Cr3+ + 3e / ⇌ / Cr /  0,74
Zn2+ + 2e / ⇌ / Zn /  0,76
2H2O + 2e / ⇌ / H2(g) + 2OH /  0,83
Cr2+ + 2e / ⇌ / Cr /  0,91
Mn2+ + 2e / ⇌ / Mn /  1,18
Aℓ3+ + 3e / ⇌ / Aℓ /  1,66
Mg2+ + 2e / ⇌ / Mg /  2,36
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

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TABLE 4B: STANDARD REDUCTION POTENTIALS

Half-reactions/Halfreaksies / (V)
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 /  2,36
Aℓ3+ + 3e / ⇌ / Aℓ /  1,66
Mn2+ + 2e / ⇌ / Mn /  1,18
Cr2+ + 2e / ⇌ / Cr /  0,91
2H2O + 2e / ⇌ / H2(g) + 2OH /  0,83
Zn2+ + 2e / ⇌ / Zn /  0,76
Cr3+ + 3e / ⇌ / Cr /  0,74
Fe2+ + 2e / ⇌ / Fe /  0,44
Cr3+ + e / ⇌ / Cr2+ /  0,41
Cd2+ + 2e / ⇌ / Cd /  0,40
Co2+ + 2e / ⇌ / Co /  0,28
Ni2+ + 2e / ⇌ / Ni /  0,27
Sn2+ + 2e / ⇌ / Sn /  0,14
Pb2+ + 2e / ⇌ / Pb /  0,13
Fe3+ + 3e / ⇌ / Fe /  0,06
2H+ + 2e / ⇌ / H2(g) / 0,00
S + 2H+ + 2e / ⇌ / H2S(g) / + 0,14
Sn4+ + 2e / ⇌ / Sn2+ / + 0,15
Cu2+ + e / ⇌ / Cu+ / + 0,16
SO + 4H+ + 2e / ⇌ / SO2(g) + 2H2O / + 0,17
Cu2+ + 2e / ⇌ / Cu / + 0,34
2H2O + O2 + 4e / ⇌ / 4OH / + 0,40
SO2 + 4H+ + 4e / ⇌ / S + 2H2O / + 0,45
Cu+ + e / ⇌ / Cu / + 0,52
I2 + 2e / ⇌ / 2I / + 0,54
O2(g) + 2H+ + 2e / ⇌ / H2O2 / + 0,68
Fe3+ + e / ⇌ / Fe2+ / + 0,77
NO + 2H+ + e / ⇌ / NO2(g) + H2O / + 0,80
Ag+ + e / ⇌ / Ag / + 0,80
Hg2+ + 2e / ⇌ / Hg(ℓ) / + 0,85
NO + 4H+ + 3e / ⇌ / NO(g) + 2H2O / + 0,96
Br2(ℓ) + 2e / ⇌ / 2Br / + 1,07
Pt2+ + 2 e / ⇌ / Pt / + 1,20
MnO2+ 4H+ + 2e / ⇌ / Mn2+ + 2H2O / + 1,23
O2(g) + 4H+ + 4e / ⇌ / 2H2O / + 1,23
Cr2O + 14H+ + 6e / ⇌ / 2Cr3+ + 7H2O / + 1,33
Cℓ2(g) + 2e / ⇌ / 2Cℓ / + 1,36
MnO + 8H+ + 5e / ⇌ / Mn2+ + 4H2O / + 1,51
H2O2 + 2H+ +2 e / ⇌ / 2H2O / +1,77
Co3+ + e / ⇌ / Co2+ / + 1,81
F2(g) + 2e / ⇌ / 2F / + 2,87

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