Pure Chemistry WA1
Name
Date
Due date
S3 Pure Chemistry – WA1
Multiple Choice Questions (15m)
1
2
The chromatogram of 4 substances is shown below.
Which substance has an Rf value of 0.713?
(
)
(
)
The diagram shows some readings in a thermometer and a measuring
cylinder.
Which row shows the correct readings for both the apparatus?
Measuring cylinder Thermometer
A) 9.0mL
43℃
B) 9.0mL
46℃
C) 8.5mL
43℃
D) 8.5mL
46℃
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3
The table below provides the density and solubility of 4 different gases.
Gas Density
Solubility
1
Denser than air
Soluble in water
2
Denser than air
Insoluble in water
3
Less dense than air Soluble in water
4
Less dense than air Insoluble in water
Which row correctly matches the method of collection of the respective
gases?
Gas
Upward
delivery
Downward delivery Displacement of water
A)
1
Yes
No
Yes
B)
2
No
Yes
Yes
C)
3
No
Yes
No
D)
4
Yes
No
No
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)
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4
A beaker of argon gas is inverted over a porous pot containing carbon
monoxide.
What happens to the liquid level at X and the corresponding explanation?
Change in liquid level
at X
Explanation
A) Rise
CO is a diatomic molecule whereas Ar is a
monoatomic atom.
B) Rise
Relative atomic mass of Ar is higher than
relative molecular mass of CO.
C) Fall
Relative atomic mass of Ar is higher than
relative molecular mass of CO.
D) Fall
Both gases are in a constant random motion.
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)
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5
A pure molten compound was heated from solid state until a change of state
has occurred. The graph trends the temperature of the compound over time.
At which region(s) of the graph is the liquid state present?
A) 1 to 2
B) 2 to 3
C) 2 to 3 and 3 to 4
D) 3 to 4
6
7
Which apparatus is most suitable in accurately measuring 30.3mL of
hydrochloric acid?
A) Measuring cylinder
B) Pipette
C) Burette
D) Beaker
(
)
(
)
(
)
4 balloons are filled with equal volume of different gases and left to idle for 4
hours.
The balloons shrunk to different extent.
Arrange the size of the balloon in decreasing order after 4 hours.
A) CO2 , Ne, NH3 , H2
B) H2 , NH3 , Ne, CO2
C) CO2 , NH3 , Ne, H2
D) H2 , Ne, NH3 , CO2
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8
9
Which of the following observations is not explained by kinetic particle
theory?
A) A teabag dipped into hot water will eventually lead to a homogenous
cup of tea.
B) Water expands in volume when frozen.
C) An inflated balloon placed in liquid nitrogen shrinks but reinflates
when returned to room temperature.
D) Gas expands when heated.
)
(
)
(
)
The following experimental set up is used to obtain carbon monoxide.
What is the main purpose of the aqueous potassium hydroxide?
A) Remove excess carbon dioxide
B) Remove water
C) Remove hydrochloric acid fumes
D) Remove carbon soot
10
(
The diagram below shows the arrangement of particles of a substance at 2
different temperatures and at the same pressure.
What is likely to be the melting and boiling point of this substance?
Melting point/℃ Boiling point/℃
A) -265
-235
B) -265
-245
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11
12
C) -270
-240
D) -260
-235
A beam of particles is passed between charged plates.
Which diagram shows how the particles are deflected as they pass through
the plate?
)
(
)
(
)
(
)
Carbon can exist as an isotope of 12, 13 and 14. Which is not a possible
relative molecular mass of carbon dioxide made from carbon isotopes?
A) 44
B) 45
C) 46
D) 47
13
(
Diamond is a giant covalent molecule made of only carbon. Carbon exist as
an isotope of C-12 and C-13. It is found that the average relative atomic
mass of carbon is 12.011.
What is the relative abundance of C-13?
A) 1.0%
B) 1.1%
C) 1.2%
D) 1.3%
14
Which particle have the least number of electrons?
A) Argon atom
B) Chloride ion
C) Sulfur atom
D) Potassium ion
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15
An atom of element X has 29 neutrons and 25 protons. How many electrons
does the ion of X have?
A) 18
B) 25
C) 26
D) 20
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(
)
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Section A (40m)
Answer all the questions in the spaces provided.
1
The time taken for a fixed volume of gas to diffuse from 1 end of the tube to another end is
recorded.
The experiment was repeated under the same conditions with different gases, and the
results obtained were recorded in the table below.
Gas
Formula
Relative molecular mass
Time taken/s
Carbon monoxide
CO
Neon
Ne
Sulfur dioxide
SO2
72
Chlorine
Cl2
83
31
20
25
(a)
Complete the table above.
[1]
(b)
Describe and explain the trend observed.
[2]
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(c)
Deduce the time taken for the diffusion of the following gases:
i)
Carbon dioxide (CO2): _________________
ii)
Ethane (C2H6): __________________
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[1]
S3 Pure Chemistry – WA1
(d)
In the space below, draw the electronic structure of Neon.
[1]
(e)
Explain why neon is inert.
[1]
_____________________________________________________________________
2
The figure below shows a pot of ethane gas, inverted over a porous pot containing neon gas.
(a)
Deduce whether the water level in the right arm of the U shaped tube would fall or rise.
Explain your answer.
[3]
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(b)
Suggest why it is not suitable to conduct the experiment with ammonia gas inside the
porous pot.
_____________________________________________________________________
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[1]
S3 Pure Chemistry – WA1
(c)
Air can be liquefied and stored in cylinders at room temperature. Suggest how this is
done and an advantage of storing air in liquid form.
[2]
_____________________________________________________________________
_____________________________________________________________________
3
Potassium exists as 3 different isotopes, K-39, K-40 and K-41. Their relative abundance can
be detected by mass spectrometry. The results of the mass spectrometry of a sample of
potassium is shown below.
(a)
Define isotopes.
[1]
_____________________________________________________________________
_____________________________________________________________________
(b)
Despite existing as isotopes, the chemical properties of potassium remains
[1]
unchanged.
_____________________________________________________________________
_____________________________________________________________________
(c)
State a physical property of metal.
[1]
_____________________________________________________________________
(d)
Which is the most abundant isotope of potassium? ___________________
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[1]
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(e)
Calculate the relative atomic mass of potassium.
K-39
K-40
K-41
93.26%
0.0117%
6.73%
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[2]
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4
A mixture of 50cm3 of propanol and 50cm3 of propanoic acid is separated using the following set
up.
Boiling point of propanol: 97℃
Boiling point of propanoic acid: 141℃
(a)
Draw in the box below, the arrangement of particles at region A and B.
[2]
(b)
Which substance would be collected first?__________________
[1]
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(c)
Draw the graph of volume of distillate collected against temperature.
(a)
Draw the dot-and-cross diagram of carbon dioxide, showing only the valence electrons. [2]
(b)
Using your knowledge of kinetic particle theory, explain why dry ice sublimes in room
temperature and pressure.
[3]
5
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
6
When bromine, Br2, is cooled, it forms a reddish brown crystal. These crystals are then heated
and the temperature is measured. The heating curve of bromine is seen in the graph below.
S3 Pure Chemistry (WA1) © The Science of Studying
[2]
S3 Pure Chemistry – WA1
(a)
Explain, in terms of kinetic particle theory, why temperature remains unchanged
between B and C.
[1]
_____________________________________________________________________
_____________________________________________________________________
(b)
How does the movement and arrangement of particles differ at point A and point D?
[2]
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
_____________________________________________________________________
(c)
7
Draw, in the space provided below, the arrangement of bromine in the gaseous state.
[1]
The structure of 2 particles are shown below.
(a)
Refer to the periodic table, state the ionic formula of each particle.
A: ______________
B: ______________
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[1]
S3 Pure Chemistry – WA1
(b)
Why do isotopes have similar chemical properties but slightly different physical
[2]
properties?
_____________________________________________________________________
_____________________________________________________________________
(c)
8
Calculate the nucleon number of both particles. Show your working below.
Complete the table below. [3]
Nuclide notation
32
Number of
proton
Number of
neutron
Number of
electron
20
20
18
S162-
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[2]
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ANSWERS
Multiple Choice Questions (15m)
1
The chromatogram of 4 substances is shown below.
Which substance has an Rf value of 0.713?
(
)
(
)
Ans: B. 20cm is the length of the filter paper. 15cm is the solvent front
(distance travelled by the solvent). The Rf value is calculated by taking the
distance travelled by the dye with respect to the distance travelled by the
solvent. Therefore, it is B as 10.7/15 = 0.713
2
The diagram shows some readings in a thermometer and a measuring
cylinder.
Which row shows the correct readings for both the apparatus?
Measuring cylinder Thermometer
A) 9.0mL
43℃
B) 9.0mL
46℃
S3 Pure Chemistry (WA1) © The Science of Studying
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C) 8.5mL
43℃
D) 8.5mL
46℃
Ans: B. Student need to know the different precision of the instrument by
checking the graduation of the apparatus itself. Every increment on both the
measuring cylinder and thermometer is 0.2. Students should also learn to
read meniscus of fluids.
3
The table below provides the density and solubility of 4 different gases.
Gas Density
Solubility
1
Denser than air
Soluble in water
2
Denser than air
Insoluble in water
3
Less dense than air Soluble in water
4
Less dense than air Insoluble in water
Which row correctly matches the method of collection of the respective
gases?
Ga
s
Upward
delivery
Downward delivery Displacement of water
A)
1
Yes
No
Yes
B)
2
No
Yes
Yes
C)
3
No
Yes
No
D)
4
Yes
No
No
Ans: B. Upward delivery = for gases less dense than air; Downward delivery
= for gases more dense than air; Displacement of water = for gases that are
not soluble in water.
4
A beaker of argon gas is inverted over a porous pot containing carbon
monoxide.
What happens to the liquid level at X and the corresponding explanation?
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(
)
S3 Pure Chemistry – WA1
Change in liquid level
at X
Explanation
A) Rise
CO is a diatomic molecule whereas Ar is a
monoatomic atom.
B) Rise
Relative atomic mass of Ar is higher than
relative molecular mass of CO.
C) Fall
Relative atomic mass of Ar is higher than
relative molecular mass of CO.
D) Fall
Both gases are in a constant random motion.
(
)
(
)
Ans: B. As CO diffuse out faster than Ar diffusing into the porous pot, the
liquid level at X would rise since there are more gas exiting than entering.
5
A pure molten compound was heated from solid state until a change of state
has occurred. The graph trends the temperature of the compound over time.
At which region(s) of the graph is the liquid state present?
A) 1 to 2
B) 2 to 3
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C) 2 to 3 and 3 to 4
D) 3 to 4
Ans: C. At the change of state, the compound exist as a mixture of solid and
liquid state. When change of state is completed, the compound will fully exist
as a liquid.
6
Which apparatus is most suitable in accurately measuring 30.3mL of
hydrochloric acid?
A) Measuring cylinder
B) Pipette
C) Burette
D) Beaker
(
)
(
)
(
)
!"#$%&'%()*%#+,--*#.%/0*12#23"%34%560*..*%2#%7'8+9:%;)21)%+,<*#%2.%.)*%+3#.%
,//03/02,.*%,//,0,.6#%.3%+*,#60*'%=2/*..*%+*,#60*%42>*?%@3-6+*#%A-2<*%87:%
8B:%C71+DE%F%"3.%#62.,5-*'
Beaker is not an accurate apparatus to measure as well due to huge
uncertainty. Measuring cylinder can measure accurately up to 0.5-1mL.
7
4 balloons are filled with equal volume of different gases and left to idle for 4
hours.
The balloons shrunk to different extent.
Arrange the size of the balloon in decreasing order after 4 hours.
A) CO2 , Ne, NH3 , H2
B) H2 , NH3 , Ne, CO2
C) CO2 , NH3 , Ne, H2
D) H2 , Ne, NH3 , CO2
Ans: A. The larger the relative molecular mass, the slower the rate of
diffusion. Therefore, CO2, Ne, NH3, H2
8
Which of the following observations is not explained by kinetic particle
theory?
A) A teabag dipped into hot water will eventually lead to a homogenous
cup of tea.
B) Water expands in volume when frozen.
C) An inflated balloon placed in liquid nitrogen shrinks but reinflates
when returned to room temperature.
D) Gas expands when heated.
S3 Pure Chemistry (WA1) © The Science of Studying
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Ans: B. When kinetic energy is introduced to matter, matter tends to expand,
particles move further apart and take up larger space and volume.
Conversely, when kinetic energy is removed from matter, particles will move
closer together and take up lesser space and volume. An anomalous
exception is water, as freezing indicates the reduction in kinetic energy of the
water molecules, yet water expands slightly and take up a larger volume
when frozen.
9
The following experimental set up is used to obtain carbon monoxide.
What is the main purpose of the aqueous potassium hydroxide?
A) Remove excess carbon dioxide
B) Remove water
C) Remove hydrochloric acid fumes
D) Remove carbon soot
Ans: B. Potassium hydroxide is a common drying agent, used to absorb
moisture.
10
(
)
(
)
The diagram below shows the arrangement of particles of a substance at 2
different temperatures and at the same pressure.
What is likely to be the melting and boiling point of this substance?
Melting point/℃ Boiling point/℃
A) -265
-235
B) -265
-245
C) -270
-240
D) -260
-235
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!"#$%G'%!.%HCI7&%F%#3-2?%#.,.*'%J6KK*#.2"K%.),.%+*-.2"K%/32".%#)36-?%5*%L%H
CI7&'%M,#*36#%#.,.*%,.%HCN7&:%#6KK*#.2"K%.),.%532-2"K%/32".%2#%OHCN7&'
11
A beam of particles is passed between charged plates.
Which diagram shows how the particles are deflected as they pass through
the plate?
(
)
(
)
(
)
Ans: C. Protons will deflect towards the negative pole, electrons will deflect
towards the positive pole. No deflection for neutrons as it is not charged.
Electrons will deflect to a larger degree than protons as it is lighter. (Relative
mass of 1/1840 vs 1)
12
13
14
Carbon can exist as an isotope of 12, 13 and 14. Which is not a possible
relative molecular mass of carbon dioxide made from carbon isotopes?
A) 44
B) 45
C) 46
D) 47
Ans: D. When carbon dioxide is made from carbon-12, 13 or 14, the relative
molecular mass is either 44, 45 and 46.
Diamond is a giant covalent molecule made of only carbon. Carbon exist as
an isotope of C-12 and C-13. It is found that the average relative atomic
mass of carbon is 12.011.
What is the relative abundance of C-13?
A) 1.0%
B) 1.1%
C) 1.2%
D) 1.3%
Ans: B
Let C-12 by x; C-13 = 100-x
x/100 x 12 + (100-x)/100 x 13 = 12.011
12x/100 + 13 - 13x/100 = 12.011
-x/100 = 12.011-13
X = 98.9%
Which particle have the least number of electrons?
A) Argon atom
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B) Chloride ion
C) Sulfur atom
D) Potassium ion
Ans: C. Sulfur atom has 16 electrons. Argon has 18 electrons, chloride ion
(gain 1 e-) has 18 electrons and potassium ion (lose 1 e-) has 18 electrons.
15
An atom of element X has 29 neutrons and 25 protons. How many electrons
does the ion of X have?
A) 18
B) 25
C) 26
D) 20
Ans: C. Atom of X has electronic configuration: 2,8,8,7. Ion of X will be
formed when X gain 1 electron to complete it’s valence shell, 2,8,8,8.
Therefore, 26 electrons.
S3 Pure Chemistry (WA1) © The Science of Studying
(
)
(
)
S3 Pure Chemistry – WA1
Section A (40m)
Answer all the questions in the spaces provided.
1
The time taken for a fixed volume of gas to diffuse from 1 end of the tube to another end is
recorded.
The experiment was repeated under the same conditions with different gases, and the
results obtained were recorded in the table below.
Gas
Formula
Relative molecular mass
Time taken/s
Carbon monoxide
CO
Neon
Ne
Sulfur dioxide
SO2
72
Chlorine
Cl2
83
31
20
25
(a)
Complete the table above. (28, 64, 71)
[1]
(b)
Describe and explain the trend observed. [2] The larger the relative molecular mass,
the longer the time taken for the gas to diffuse across from one end to another end. [1].
The larger the relative molecular mass, the slower the rate of diffusion. [1]
[2]
(c)
Deduce the time taken for the diffusion of the following gases:
[1]
(d)
i)
Carbon dioxide (CO2): between 40-60s
ii)
Ethane (C2H6): between 35-45s
In the space below, draw the electronic structure of Neon.
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[1]
S3 Pure Chemistry – WA1
(e)
2
Explain why neon is inert. [1] Neon already has full valence shell/exist in the most
stable electronic configuration/stable state.
[1]
The figure below shows a pot of ethane gas, inverted over a porous pot containing neon gas.
(a)
Deduce whether the water level in the right arm of the U shaped tube would fall or rise.
Explain your answer.
Water level in the right arm of the U-tube falls [1]
Relative atomic mass of Neon (20) lesser than relative molecular mass of ethane (30).
[1]
Neon diffuse faster out of the porous pot than ethane diffusing into the porous pot.
Decrease in pressure draws water column towards the porous pot. [1]
[3]
(b)
Suggest why it is not suitable to conduct the experiment with ammonia gas inside the
porous pot. Ammonia is soluble in water.
[1]
(c)
Air can be liquefied and stored in cylinders at room temperature. Suggest how this is
done and an advantage of storing air in liquid form. Using high pressure [1]. Allows
more air particles to be stored in a fixed volume in liquid form. [1]
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[2]
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3
Potassium exists as 3 different isotopes, K-39, K-40 and K-41. Their relative abundance can
be detected by mass spectrometry. The results of the mass spectrometry of a sample of
potassium is shown below.
(a)
Define isotopes.[1] Elements with the same number of protons but different number of
[1]
neutrons.
(b)
Despite existing as isotopes, the chemical properties of potassium remains
[1]
unchanged. Explain why is this so. [1] The number of protons and electrons is the
same. Isotopes have same number of valence electrons despite having different
number of neutrons, therefore, participates in the similar chemical reactions.
(c)
State a physical property of metal. [1] Soft metal, low density, low melting and boiling
point, can conduct heat and electricity, ductile, malleable.[Any one]
[1]
(d)
Which is the most abundant isotope of potassium? [1] Potassium- 39
[1]
(e)
Calculate the relative atomic mass of potassium.
[2]
K-39
K-40
K-41
93.26%
0.0117%
6.73%
39 x (93.26/100) + 40 x (0.0117/100) + 41 x (6.73/100) = 36.3714 + 0.00468 + 2.7593
= 39.1
4
A mixture of 50cm3 of propanol and 50cm3 of propanoic acid is separated using the following set
up.
Boiling point of propanol: 97℃
Boiling point of propanoic acid: 141℃
S3 Pure Chemistry (WA1) © The Science of Studying
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(a)
Draw in the box below, the arrangement of particles at region A and B.
[2]
(b)
Which substance would be collected first? Propanol
[1]
(c)
Draw the graph of volume of distillate collected against temperature.
[3]
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5
6
(a)
Draw the dot-and-cross diagram of carbon dioxide, showing only the valence
electrons.
[2]
(b)
Using your knowledge of kinetic particle theory, explain why dry ice sublimes in room
temperature and pressure. [2]
At room temperature and pressure, the weak intermolecular forces of attraction
between molecules of carbon dioxide are easily overcome [1], allowing carbon dioxide
molecules to transit from a solid state in dry ice to a gaseous state, moving about
randomly and rapidly at all directions, without going through the liquid state. [1]
[2]
When bromine, Br2, is cooled, it forms a reddish brown crystal. These crystals are then heated
and the temperature is measured. The heating curve of bromine is seen in the graph below.
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(a)
(b)
Explain, in terms of kinetic particle theory, why temperature remains unchanged
between B and C.
Heat energy is absorbed from surrounding to overcome intermolecular forces of
attraction between bromine molecules [1]
[1]
How does the movement and arrangement of particles differ at point A and point D?%!.% [2]
!%F%P250,.*%,536.%42>*?%/3#2.23":%1-3#*-Q%/,1<*?%2"%,"%30?*0-Q%,00,"K*+*".%R8S
!.%T%F%U3--%,"?%#-2?*%3@*0%3"*%,"3.)*0:%1-3#*-Q%/,1<*?%2"%,"%?2#30?*0-Q%,00,"K*+*".'%
R8S
(c)
7
Draw, in the space provided below, the arrangement of bromine in the gaseous state.
[1]
The structure of 2 particles are shown below.
(a)
Refer to the periodic table, state the formula of each particle.
A: Na+ and B: F-
[1]
(b)
Why do isotopes have similar chemical properties but slightly different physical
properties?
Isotopes have similar chemical properties as they have the same number of valence
electrons [1]
Different relative atomic masses give rise to slight differences in physical properties
such as melting/boiling points and densities. [1]
[2]
(c)
Calculate the nucleon number of both particles. Show your working below.
For sodium: 11+ 12 = 23
[2]
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For fluorine: 9 + 10 = 19
8
Complete the table below. [3]
Nuclide notation
Number of
proton
Number of
neutron
Number of
electron
32
S162-
16
16
18
Ca202+
20
20
18
40
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S3 Pure Chemistry – WA1
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