2015 HIGHER SCHOOL CERTIFICATE EXAMINATION
Chemistry
4
456
12345678
4
Centre Number
C
Section I (continued)
Part B – 55 marks
Attempt Questions 21–31
Allow about 1 hour and 40 minutes
for this part
Student Number
Student, Sample
ple
Answer the questions in the spaces
provided. These spaces provide
guidance for the expected length of
response.
E
PL
Extra writing space is provided on
pages 27 and 28. If you use this space,
clearly indicate which question you
are answering.
M
Write your Centre Number and
Student Number at the top of this
page.
SA
Do NOT write in this area.
Show all relevant working in questions
involving calculations.
Please
turn
P
tu over
– 13 –
Office Use Only – Do NOT write anything, or make any marks below this line.
2061
15050
456
12345678
004753410
4393310351
E
SA
M
Do NOT write in this area.
PL
BLANK PA
PAGE
– 14 –
Office Use Only – Do NOT write anything, or make any marks below this line.
2381310356
Question 21 (3 marks)
The transuranic artificial element curium–242 can be produced in two w
ways.
The nuclear equations for the two processes are given below.
3
Process A
241
95 Am
+
1
0n
→
242
95 Am
→
242
96 Cm
+
242
96 Cm
+
0
−1 e
Process B
239
94 Pu
+
4
2 He
→
1
0n
Compare these two processes of production for the element
curium–242.
lem curiu
uri
E
.........................................................................................................................................
..
......................
.....................
..
PL
.........................................................................................................................................
..
........................
................
..
.........................................................................................................................................
..
........................
...........
..
.........................................................................................................................................
.
.......................
.....
.
M
.........................................................................................................................................
..
........................
...........
..
.........................................................................................................................................
..
........................
...................
..
.........................................................................................................................................
.
.......................
.....
.
SA
Do NOT write in this area.
.........................................................................................................................................
.
.......................
......
.
– 15 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
1159310358
Question 22 (6 marks)
A student performed a first-hand investigation to determine the quantitative
ive relationship
between heat of combustion and molecular mass of alkanols. The student did
id this by burning
different alkanols to heat water as shown in the diagram below. The ca
calculated heats of
combustion for four of the alkanols are given in the table.
Thermometer
om
ak containing water
Beaker
E
W gauze
auz
auze
Wire
Tripod
methanol
PL
Calculated
Calculate
culat heat
at
of combustion
ccom
ion
(k
(kJ mol−11)
Theoretical heat
of combustion
(kJ mol−1)
32
150
50
726
46
950
1367
SA
ethanol
Mo
Molecularr
masss
(g mol
ol−1)
M
Alkanol
-1propan-1-ol
60
1500
2021
anbutan-1-ol
74
2250
2676
on 22 continues on page 17
Question
– 16 –
Office Use Only – Do NOT write anything, or make any marks below this line.
4873310354
Do NOT write in this area.
Spiri burner
burner
ner
Spirit
ntaining alkanol
nol
containing
Question 22 (continued)
(a)
On the grid below, graph both the calculated and the theoretical heat
hea of
combustion against the molecular mass of the alkanols.
3
Heat of combustion versus molecular mass
PL
Molecular
M
ular
lar ma
mass
(gg mol
mo –1)
Discuss the validity of thee student’s
s
t’s investigation.
nvestigat
3
M
(b)
...............................................................................................................................
..
........................
....................
..
...............................................................................................................................
.
.......................
....
.
...............................................................................................................................
..
........................
.................
..
SA
Do NOT write in this area.
E
Heat of
combustion
(kJ mol–1)
...............................................................................................................................
..
........................
....................
.
...............................................................................................................................
.
........................
...................
.
...............................................................................................................................
..
.......
........
..
...............................................................................................................................
..
.
...............................................................................................................................
.
End of Question 22
– 17 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
7471310351
Question 23 (3 marks)
This diagram shows a town situated near agriculture and industry.
Car battery
factory
Agricultural
land
ek
Cre
Agricultural
ric
land
(a)
E
M
The town relies on the river for its water
wa supply.
pply.
Identify ONE chemical species
sp
that could be a contaminant
c
min of the water supply.
1
(b)
SA
...............................................................................................................................
..
........................
......
.
Explain the need
eed to monitor
onitorr the levels of a contaminant
co
in water supplies.
2
...............................................................................................................................
.
.......................
........................
..
...............................................................................................................................
..
....................
..................
..
...............................................................................................................................
.
..
.
– 18 –
Office Use Only – Do NOT write anything, or make any marks below this line.
9964310350
Do NOT write in this area.
PL
Town
River
Town water
supply
Question 24 (5 marks)
A solution contains carbonate, chloride and sulfate ions.
5
Describe a sequence of tests that could be used to confirm the presence of each of
these ions. Include ONE relevant chemical equation.
.........................................................................................................................................
..
.........................................................................................................................................
.
.........................................................................................................................................
..
.........................................................................................................................................
..
.........................................................................................................................................
.
.
E
.........................................................................................................................................
..
................
............
..
PL
.........................................................................................................................................
.
........................
....................
.
.........................................................................................................................................
..
........................
......................
..
M
.........................................................................................................................................
..
........................
.........
.
SA
Do NOT write in this area.
.........................................................................................................................................
..
........................
...........
.
– 19 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
5638310354
Question 25 (4 marks)
Under conditions of low oxygen levels, octane can undergo incomplete combustion
bu
according to the following chemical equation:
2C8H18(l ) + 17O2(g)
(a)
6C(s) + 4CO(g) + 6CO2(g) + 18H
1 2O(l )
Explain the need to monitor this process.
2
..
...............................................................................................................................
.
...............................................................................................................................
..
.
...............................................................................................................................
PL
2
...............................................................................................................................
.
.......................
.
...............................................................................................................................
..
........................
.......
..
M
...............................................................................................................................
..
........................
.........
..
...............................................................................................................................
.
.................
.......................
.
– 20 –
Office Use Only – Do NOT write anything, or make any marks below this line.
9657310359
Do NOT write in this area.
ced if 4.2
2 moles of octane
ctane are com
combusted
Calculate the mass of soot (C(s)) produced
in this way.
SA
(b)
E
..
.............
...........
.
...............................................................................................................................
Question 26 (6 marks)
A first-hand investigation to produce an ester is to be carried out in a sc
school
laboratory, using an alkanol, an alkanoic acid and a suitable catalyst.
(a)
Name an ester that could be produced in a school laboratory.
1
...............................................................................................................................
..
(b)
Describe how potential hazards associated with the three ch
chemicals required for
this investigation could be addressed.
5
...............................................................................................................................
..
...............................................................................................................................
.
....
.....
.
E
...............................................................................................................................
..
......................
.....................
..
PL
...............................................................................................................................
.
........................
................
..
...............................................................................................................................
..
........................
...........
..
...............................................................................................................................
.
.......................
.....
.
M
...............................................................................................................................
.
........................
..........
..
...............................................................................................................................
..
........................
...................
..
...............................................................................................................................
.
.......................
.....
.
SA
Do NOT write in this area.
...............................................................................................................................
.
........................
.....
.
– 21 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
6157310351
Question 27 (6 marks)
Limestone (CaCO3) contributes to the hardness of water by releasing Ca2+ ion
ions in
water. The chemical equation for this exothermic reaction is shown.
CaCO3(s) + H2O(l ) + CO2(g) W Ca2+(aq) + 2HCO
O3−(aq)
(a)
Explain why increasing the temperature of hard water would re
reduce its hardness.
2
..
...............................................................................................................................
.
...............................................................................................................................
..
.
...............................................................................................................................
4
.
........................
.............
..
...............................................................................................................................
..
........................
............
..
...............................................................................................................................
.
..................
.......................
.
...............................................................................................................................
M
..
........................
............
..
...............................................................................................................................
..
........................
....................
..
...............................................................................................................................
.
.......................
....
.
...............................................................................................................................
..
........................
................
..
...............................................................................................................................
...............................................................................................................................
..
........................
....................
..
– 22 –
Office Use Only – Do NOT write anything, or make any marks below this line.
1086310357
Do NOT write in this area.
PL
cop (AAS)
AS) could be us
use
Describe how atomic absorption spectroscopy
used to me
measure
duc its hardness.
the effectiveness of heating water to reduce
SA
(b)
E
..
.............
...........
.
...............................................................................................................................
Question 28 (5 marks)
A galvanic cell has been constructed as shown in the diagram.
V
X metal
(anode)
Cu metal
(cathode)
KNO3(aq)
salt bridge
Colourless
solution
Blue
solution
Explain the colour change in the copper
er half-cell
cell
ell as the reaction
reactio proceeds.
oce
PL
2
...............................................................................................................................
.
.......................
........................
.
...............................................................................................................................
..
........................
...........
..
M
...............................................................................................................................
..
........................
.......................
.
...............................................................................................................................
.
........................
...........
.
(b)
The theoretical standard
and
potential
otential for this galvanic
ani cell is 2.02 V.
4
SA
Do NOT write in this area.
(a)
m L–1 Cu
Cu(NO3)2(aq)
C
1.00 mol
E
1.0 mol L–1 nitrate salt
solution of X
Identify metal X and justify
ustify your answer.
answ
...............................................................................................................................
.
.......................
.
...............................................................................................................................
..
..................
...................
..
...............................................................................................................................
..
..
..
...............................................................................................................................
.
.
...............................................................................................................................
..
...............................................................................................................................
..
– 23 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
6784310357
Question 29 (5 marks)
An experiment was performed to model the formation of acid rain.
5
A sample of sulfur was burned on a metal spoon. While alight, it was placed
ced in a gas
jar with some dry litmus paper.
Lid
Metal
Me spoon
Gas jar
E
Burning sulfur
Bur
Burnin
When a fine mist of water was sprayed
d iinto the
hee jar, the litmus paper
er tturned red.
M
Assess the suitability of this experiment
per
t as a model for tthe formation
orm
of acid rain.
.........................................................................................................................................
..
.....................
........................
..
.........................................................................................................................................
..
........................
......
..
SA
.........................................................................................................................................
.
.......................
..................
.
.........................................................................................................................................
..
........................
.................
..
.........................................................................................................................................
..
........................
...................
..
.........................................................................................................................................
.
.........
.......
.
.........................................................................................................................................
..
..
.........................................................................................................................................
..
..
.........................................................................................................................................
.
.
.........................................................................................................................................
..
– 24 –
Office Use Only – Do NOT write anything, or make any marks below this line.
7927310357
Do NOT write in this area.
PL
Dry litm
litmus paper
ape
Question 30 (5 marks)
A batch of dry ice (solid CO2) was contaminated during manufacture. To determine
ter
its purity, the following steps were carried out.
Step 1: A 0.616 gram sample of the contaminated dry ice was
placed in a clean, dry flask.
Step 2: 50.00 mL of 1.00 mol L−1 sodium hydroxide w
was added to
the flask. The sodium hydroxide was in excess.
ces
car
Step 3: The flask was sealed to prevent loss of carbon
dioxide gas
mpl
and the reaction allowed to reach completion,
according to
this equation:
2NaOH(aq) + CO2(s)
Na2CO3(aq) + H2O(l )
PL
(a)
Calculate the number of moles of NaOH
H added in
i Step 2.
1
M
...............................................................................................................................
.
........................
.......................
.
...............................................................................................................................
.
........................
...........
..
(b)
en
urity by mass of
o this ba
Calculate the percentage
purity
batch of dry ice.
4
SA
Do NOT write in this area.
E
rox
was
as titrated aga
Step 4: The remaining sodium hydroxide
against a
−1
hydrochloric
loric acid.
cid. The aaverage
ge
1.00 mol L solution of hyd
volume of HCl used was 27.60
27 mL.
mL
..
........................
..........
..
...............................................................................................................................
.
......................
.......................
.
...............................................................................................................................
..
......................
...................
..
...............................................................................................................................
..
.....
..
..
...............................................................................................................................
...............................................................................................................................
.
.
...............................................................................................................................
..
...............................................................................................................................
..
...............................................................................................................................
.
– 25 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
9403310358
Question 31 (7 marks)
With reference to the underlying chemistry and with relevant equations, assess
ses the
impacts on society of TWO uses of ethanol.
7
.........................................................................................................................................
..
.........................................................................................................................................
..
.........................................................................................................................................
.
.........................................................................................................................................
..
.........................................................................................................................................
..
.........................................................................................................................................
.
.
E
.........................................................................................................................................
..
............
..............
..
.........................................................................................................................................
..
........................
..............
..
.........................................................................................................................................
..
........................
......................
..
.........................................................................................................................................
..
........................
............
.
.........................................................................................................................................
.
.......................
........................
.
M
.........................................................................................................................................
..
........................
............
..
.........................................................................................................................................
..
........................
................
.
SA
.........................................................................................................................................
.
.........
........................
.
.........................................................................................................................................
..
........................
........
..
.........................................................................................................................................
.
........................
.
.........................................................................................................................................
.
...................
.................
..
– 26 –
Office Use Only – Do NOT write anything, or make any marks below this line.
8246310352
Do NOT write in this area.
PL
.........................................................................................................................................
.
....
.......................
.
Section I Part B extra writing space
PL
M
SA
Do NOT write in this area.
E
If you use this space, clearly indicate which question you are answering.
– 27 –
Office Use Only – Do NOT write anything, or make any marks below this line.
004753410
9248310355
Section I Part B extra writing space
SA
M
Do NOT write in this area.
PL
E
If you use this space, clearly indicate which question you are answering.
– 28 –
© 2015 Board of Studies, Teaching and Educational Standards NSW
Office Use Only – Do NOT write anything, or make any marks below this line.
8455310354