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p2 p3 p4 p5 p6 p7 Total
Cambridge Chemistry Challenge Lower 6th
June 2015
Marking scheme for teachers(please also read the additional instructions)
C L63
Page 1
16 12 6 10 3 6013
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1(a)(i)
equations (underline reduced element):
1(b) dot & cross diagrams
1(c) neutral compound isoelectronic with nitrate(III) ion:
formula: name:
(i) formula = (ii) formula =
(iii) formula =
from mercury(II) oxide:
(ii) from silver(I) carbonate:
(iii) from potassium nitrate(V):
(iv) from sulfuric acid and manganese(IV) oxide:
Page 2
2
2
2
2
2
22HgO 2Hg + O2
2Ag2CO3 4Ag + 2CO2 + O2
2KNO3 2KNO2 + O2
CO32–
2H2SO4 + 2MnO2 2MnSO4 + 2H2O + O2
2
2
Page total16
[ Half quantities accepted. 1 mark for equation; 1 for underlined ]
[could beswapped ]
OC
O O×
×× × × ××
×× ××××
×
×× ××
O4
O3[also allow CF2, difluorocarbene, or O=N–F, nitrosyl fluoride]
ozone
OO
O O×
×× × ×× ××××××
×
×
×× ××
BO33–
OB
O O×
×× × × ××
×× ××××
×
×× ××
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1(d) activation energy for puckered-ring O4 from O2:
1(e) A =
C =
B =
Page 3
1(f) tick the shape(s) most consistent with the data:
1(g) time taken:
1
3
4
O2
puckeredring O2
pinwheelO2
= 480.0 – 89.3 + 48.7 = 439.4 kJ mol–1
4
Page total12
89.3
480.0
[1 mark if all three correct]
[2 marks if worked outstandard enthalpy of
formation of puckered-ring O2 = 390.7 kJ mol–1]
[1 mark each; lose 1 mark for any wrong (down to zero)]
[lose 1 mark each time a power of ten is incorrectly used]
k.e. of O4 molecule = 4.00 keV = 4000 × 1.602 × 10–19 J
mass of 18O4 = 18.00 × 4 g mol–1 ≡ kg molecule–1
k.e. = ½ m v2 ∴ v = 2 × (k.e.)m
16O2+ 18O2
+
16O218O2
+
48.7
Ea
Ea
18.00 × 4
= 1.1956 × 10–25 kg
= 9.66 × 10–7 s (≈ 0.1 µs)
= 103 500 m s–1
time of flight =
6.022 × 1023 × 103
0.100 m
103 500 m s–1
v = 2 × 6.408 × 10–16
1.1956 × 10–25
= 6.408 × 10–16 J
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2(a)
2(b)
Free radical
circle one or more:
2(c) three alkenes:
Nucleophilic
Electrophilic Addition
Substitution
i)
Page 4
ii)
iii) iv)
2(d)i) ii)
iii) iv)
2
3
4
zero 3, 5
4, 6, 9 1, 8
4
Page total13
[–1 mark for any wrong down to zero]
[zero marks for part containing missing / additional wrong answers]
[zero marks for part containing missing / additional wrong answers]
14, 18
12, 18
13, 16
16, 17
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2(e)
i) connect: &
ii) Carbocation B+:
for α-terpineol
Page 5
2(f)
i) connect: &
ii) Carbocation C+:
for borneol
2(g)
i) connect: &
ii) Carbocation D+:
for β-pinene
2
2
2
Page total6
d j
A B
B C
cyclisation
[only structure of B+ required no labels on it needed]
[only structure of C+ required no labels on it needed]
ab
cd
j
i
gh
f
e
ab
c
d j
igh
f
e
c g
cyclisation
a bc
de
f g
h
j
i
a bc
de
fg
h
ji
B D
[only structure of D+ required no labels on it needed]
c i
cyclisation
a bc
de
f g
h
j
i
a ab
b
cc
d
d
e e
f fgg
h h
j j
ii
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2(h)
Cation U+:
Page 6
2(i)
2(j) Compound X
Compound Y
connections:
3
3
3
1
Page total10
c to gl to ft to k
q to kalso allowed
instead oft to k
[only connections required-1 mark for any incorrect
down to zero]
[1 mark for enol]
H
H H
W
V
ab
c
d
ef
g
hi
j
k
l
mn
o
p
q
r
s
t
u
ab
c
d
ef
g
h
ij
kl
mn
o
p
q
r
s
t
u
H
H H
HO
H
H H
OH
H
H H
O
OO
O HH
H
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Page 7
2(j) Anion Z–
3
Page total3
H
H H
O
OO
H
H H
O
OO
or
[ either structure fine ]
H H