MC 2021 Chem Paper 1B
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B
METHODIST COLLEGE
HONG KONG DIPLOMA OF SECONDARY EDUCATION EXAMINATION
F.6 MOCK EXAMINATION
CHEMISTRY PAPER 1
SECTION B : Question-Answer Book B
This paper must be answered in English. INSTRUCTIONS FOR SECTION B
(1)
After the announcement of the start of the examination, you should write your name, class and class number in the space provided on this page.
(2)
Refer to the general instructions on the cover of the Question Paper for Section A.
(3)
This section consists of TWO parts, Part I and Part II. (4)
Answer ALL questions in both Parts I and II. 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.
(5)
An asterisk (*) has been put next to the questions where effective communication is assessed.
(6)
Supplementary answer sheets will be provided on request. Write your name, class, class number and the question number on each sheet, and fasten them with a string INSIDE this Question-Answer Book.
(7)
No extra time will be given to candidates for writing the personal information or filling in the question number boxes after the ‘Time is up’ announcement. Name:
Class (Class no.)
F.
6
( )
Section
Question No.
Marks
A
1 – 36
/
36
B
1
/
5
2
/
6
3
/
7
4
/
9
5
/
5
6
/
7
7
/
11
8
/
6
9
/
7
10
/
6
11
/
6
12
/
4
13
/
5
TOTAL
/120
2021-DSE
CHEM
PAPER 1B
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EXAM1
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Answers written in the margins will not be marked.
PART I
Answer ALL
questions. Write your answers in the spaces provided.
1.
Silicon carbide, SiC, can be made by heating pure sand, which is made of silicon dioxide, with carbon at a very high temperature. Carbon monoxide is also produced during the process.
(a)
Write a chemical equation for the formation of silicon carbide from pure sand.
(1 mark)
(b)
Below is the structure of silicon carbide, which is very similar to that of the diamond.
Name the type of structure that silicon carbide has.
(1 mark)
(c)
Sandpaper is made by sticking several thin layers of silicon carbide together.
(i)
When we study the reaction of a metal with oxygen in an experiment, the metal is rubbed with sandpaper first. What is the purpose of this action?
(ii)
Suggest ONE property of silicon carbide which makes it suitable for this purpose.
(2 marks)
(d)
Explain whether silicon dioxide can conduct electricity.
(1 mark)
silicon atom
carbon atom
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Answers written in the margins will not be marked.
2.
Zinc can protect iron from rusting. When galvanized iron is exposed to moist air for a period of time, it turns white due to the formation of zinc carbonate.
(a)
Suggest how to show the presence of carbonate ion in the white substance. Write an ionic equation for the reaction involved.
(2 marks)
(b)
* Explain why a galvanized iron object does not rust easily when zinc layer is fully covered iron or even if the zinc layer is damaged.
(4 marks)
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EXAM1
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Answers written in the margins will not be marked.
3.
An oxide of iron is reduced to iron using the following set-up:
(a)
Draw the electron diagram of a carbon monoxide molecule, showing electrons in the outermost shells only
.
(1 mark)
(b)
With the aid of a chemical equation, state the function of limewater in the set-up.
(2 marks)
(c)
Carbon monoxide is highly toxic. Suggest one safety precaution in carrying out this experiment besides carrying the experiment in fume cupboard.
(1 mark)
(d)
Let the chemical formula of the oxide be Fe
x
O
y
. Write a chemical equation for the reaction between the oxide and carbon monoxide in terms of x
and y
.
(1 mark)
to fume cupboard
combustion tube
carbon monoxide
heat
oxide of iron
limewater
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(e)
1.60 g of the oxide is heated until red hot. Carbon monoxide is then passed over the heated oxide and 1.12 g of iron is obtained. Calculate the empirical formula of this oxide.
(Relative atomic masses: O = 16.0, Fe = 55.8)
(2 marks)
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Answers written in the margins will not be marked.
4.
Glycolic acid is a weak acid that can be found in some skin-care products. The structure of glycolic acid is shown below.
To be regarded as non-hazardous, the amount of glycolic acid in skin-care products should not exceed 12 g per 100 cm
3
.
(a)
Explain why glycolic acid is regarded as a monobasic acid.
(1 mark)
(b)
Explain, with the aid of a chemical equation, whether 0.01 M glycolic acid solution has a pH greater than, smaller than or equal to 2.
(2 marks)
(c)
To determine the amount of glycolic acid in a toner, 7.50 cm
3
of the toner is diluted to 100.0 cm
3
using distilled water. Four portions of 25.0 cm
3
of the diluted solution are titrated with 0.150 M potassium hydroxide solution. The average volume of the potassium hydroxide solution required is 21.40 cm
3
.
(i)
Write a full chemical equation for the reaction involved in the titration.
(ii)
Suggest a suitable indicator for the titration.
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S6-20
20-21
-DSE-CHEM M
EXAM1
B/P.
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Answers written in the margins will not be marked.
(iii)
Determine whether the toner is hazardous from the titration results.
(Molar mass of glycolic acid = 76.0 g mol
−
1
)
(4 marks)
(d)
For the titration in (c), the pipette used to transfer the diluted solution is rinsed with water only. Explain how this practice will affect the titration result.
(2 marks)
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5.
The structures of alkenes A
and alkene B
are shown below.
Alkene A
:
Alkene B
:
CH
2
= CH
2
where represents an alkyl group
Under suitable conditions, the two alkenes can polymerize to form a series of polymers. The polymer
chains may contain the two alkenes in different ratios. A part of the polymer chain is shown as follows:
(a)
Draw the structure of ONE other possible repeating unit, which consists of alkene A
and alkene B
in different ratios. Show 3 monomers in the repeating units. (1 mark) (b)
Name the type of polymerization involved in forming this polymer. (1 mark)
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(c)
Why does the polymer chain contain alkene A
and alkene B
in different ratios? (l mark) (d)
The polymer is non-toxic and can be used to manufacture take-away hot food containers. Suggest another property that makes it suitable for the task. (1 mark)
(e)
Corrosion resistant metals are not used to manufacture take-away hot food containers. Give a reason for this. [Note: You do not need to consider the price of the metals.] (1 mark)
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S6-20
20-21
-DSE-CHEM M
EXAM1
B/P.
10 Answers written in the margins will not be marked.
Answers written in the margins will not be marked.
6.
It is very difficult to determine the enthalpy change of decomposition of copper(II) carbonate directly. (a)
According to definition, under which condition could the ‘heat change’ of a reaction be regarded as the ‘enthalpy change’?
(1 mark)
(b)
Suggest why it is difficult to determine directly the enthalpy change of decomposition of copper(II) carbonate.
(1 mark)
(c)
A student carried out two experiments.
Experiment 1
Reaction of copper(II) carbonate with sulphuric acid
CuCO
3
(s) + H
2
SO
4
(aq) CuSO
4
(aq) + H
2
O(l) + CO
2
(g)
Experiment 2
Reaction of copper(II) oxide with sulphuric acid
CuO(s) + H
2
SO
4
(aq) CuSO
4
(aq) + H
2
O(l)
In Experiment 1
, 3.58 g of CuCO
3
(s) was added to excess H
2
SO
4
(aq) were placed in a polystyrene foam cup. The experimental data obtained are shown below:
Initial temperature of the reacting solution
24.5 o
C
Final temperature of the reacting solution
30.7 o
C
Mass of the resulting solution
54.0 g
Specific heat capacity of the contents
4.18 J g
-1
K
-1
Molar mass of CuCO
3
123.5
g mol
-1
Calculate the enthalpy change of reaction between copper(II) carbonate and sulphuric acid, in kJ mol
–1
.
(2 marks)
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(d)
Suggest why using a polystyrene foam cup, rather than a glass beaker, was likely to give a more accurate answer for the enthalpy changes.
(1 mark)
(e)
In another experiment performed under the same conditions, the enthalpy change of the reaction between CuO(s) and H
2
SO
4(
aq) was found to be –56.1 kJ mol
–1
. Calculate the enthalpy change of decomposition of CuCO
3
(s) under the experimental conditions.
(2 marks)
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7.
Virus that can cause influenza has an oil-based coating.
(a)
Washing hands with soapy detergent is important to help reduce influenza infection caused by the virus. Suggest why soapy detergent can destroy the virus. (1 mark)
(b)
Chlorine bleach can also help reduce influenza infection caused by the virus.
(i)
In the laboratory, chlorine gas reacts with dilute sodium hydroxide to give sodium chloride and sodium hypochlorite which can be used as chlorine bleach. Write a chemical equation for the reaction, showing all state symbols.
(1 mark)
(ii)
Explain whether the above reaction is a disproportionation in term of oxidation numbers.
(2 marks)
(c)
Chlorine bleach is a common household chemical. However, it is considered to be environmentally unfriendly due to the formation of toxic by-products, such as dioxin. A good alternative is hydrogen peroxide bleach. A molecule of hydrogen peroxide can be represented by the structure shown.
(i)
Identify, with explanation, the polar bond(s) in hydrogen peroxide.
(2 marks)
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EXAM1
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(ii)
Hydrogen peroxide dissolves in water by forming hydrogen bond. Draw a diagram to show how one molecule of hydrogen peroxide interacts with one molecule of water. Include all lone pairs and partial charges in your diagram.
(2 marks)
(iii)
It is suggested that hydrogen peroxide is a polar liquid. Describe how you can carry out an experiment to test whether a liquid is polar.
(2 marks)
(iv)
The following equation shows the reaction of hydrogen peroxide with chloride ions.
H
2
O
2
(aq) + 2Cl
−
(aq) + 2H
+
(aq) →
Cl
2
(g) + 2H
2
O(l)
Compare the oxidizing power of hydrogen peroxide with chlorine.
(1 mark)
8.
The diagram below shows the set-up used in performing a microscale experiment of electrolysis of
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5.00 mol dm
–3 copper(II) chloride solution. 5.0 mol dm
–3
copper(II) chloride solution was placed between two carbon electrodes in a Petri dish. The dish was covered with its lid and a current was passed through the solution.
(a)
State, with explanation, the expected observation(s) at electrode X
.
(2 marks)
(b)
Write a half equation at electrode Y
.
(1 mark)
(c)
State the expected observation of the KBr(aq). Write the ionic equation for the reaction involved.
(2 marks)
(c)
Suggest ONE advantage of microscale experiments.
(1 mark)
END OF PART I
PART II
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9. The chemical equation of dissociation of water is shown below:
H
2
O(l) H
+
(aq) + OH
−
(aq)
Under fixed conditions, [H
2
O(l)] can be considered as a constant. In consideration of the definition of K
c
, [H
+
(aq)][OH
–
(aq)] would also be a constant.
At 25 °C, [H
+
(aq)][OH
–
(aq)] is 1.00 x 10
–14
mol
2
dm
–6
.
At 37 °C, [H
+
(aq)][OH
–
(aq)] is 2.40 x 10
–14
mol
2
dm
–6
.
At 60 °C, [H
+
(aq)][OH
–
(aq)] is 9.31 x 10
–14
mol
2
dm
–6
.
(a) Explain whether the dissociation of water is an exothermic or endothermic process.
(2 marks)
(b) (i) Determine the pH of pure water at body temperature, 37 °C
. (2 marks)
(ii) Explain whether pure water is neutral at 37
o
C.
(1 mark)
(c) Ammonium sulphate ((NH
4
)
2
SO
4
) is added to distilled water. After some times, the pH of the solution is measured. It is found that the pH value has dropped. Explain the phenomenon with the aid of an ionic equation.
(2 marks)
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-DSE-CHEM M
EXAM1
B/P.
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10.
Bromine can react with methanoic acid according to the following equation:
Br
2
(aq) + HCOOH(aq) 2Br
–
(aq) + 2H
+
(aq) + CO
2
(g)
(a)
What is the maximum volume of gas at room temperature and pressure when 3.20 g of bromine is reacted? (Relative atomic mass: Br = 79.9;
molar volume of gas at room temperature and pressure = 24.0 dm
3
mol
–1
)
(2 marks)
(b)
Suggest how the concentration of Br
2
can be monitored. (1 mark)
(c)
The variation of concentration of bromine with time shown below is obtained in an experiment. The dotted line is the tangent to the curve at 400 s.
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From the graph, determine the instantaneous rate of consumption of bromine at 400 s. (1 mark)
(d) In another experiment, the variation of concentration of Br
-
in the reaction mixture with time is recorded.
The experiment is repeated with the same set-up under the same reaction conditions, but using half of the original concentration of bromine.
(i)
Draw on the above graph, a new curve (with dotted lines “----”) that shows the variation of the concentration of Br
-
in the reaction mixture with time. (Assume that methanoic acid is in excess in both experiments.)
(ii)
Explain the effect of using a lower concentration of bromine on the reaction rate.
(2 marks)
11.
Geraniol is an alcohol that can be found in rose oil. The skeletal formula of geraniol is shown Concentration of Br
-
Time
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below.
(a)
Name the type of isomerism that exists in geraniol.
(1 mark)
(b)
To which class of alcohols does geraniol belong?
(1 mark)
(c)
Geraniol can be converted to citronellal, which is an aldehyde. Citronellal has a smell of lemon and is commonly used in mosquito repellent. The synthetic pathway of citronellal is shown below.
(i)
State the type of reaction involved in step 1
.
(ii)
In step 2
, citronellal is distilled out as soon as it forms.
(1)
Suggest why heating under reflux is NOT preferred in this step.
(2)
State the expected observation in step 2
.
(iii)
Write the structural formula of citronellal.
(4 marks)
heat
Citronellal
Cr
2
O
7
2
−
(aq)/H
+
(aq)
Step 2 Step 1
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12.
When heating calcium ethanoate strongly, acetone is produced. Acetone (propanone) is a common solvent used in the school laboratory.
(a)
Write a chemical equation for the thermal decomposition of calcium ethanoate.
(1 mark)
(b)
Acetone can be converted to isopropyl alcohol. It can be used as hand sanitizers to help stop the spread of COVID-19.
(i)
What is the systematic name of isopropyl alcohol?
(ii)
Suggest the reagents required for the conversion of acetone to isopropyl alcohol.
(iii)
Explain whether isopropyl alcohol can rotate the plane of polarized light.
(3 marks)
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13.
* Arrange sodium, magnesium, silicon and phosphorus in ascending order of electrical conductivity at room conditions, and explain your answer in terms of bonding and structure.
(5 marks)
END OF PART II
END OF SECTION B
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