mark

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

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[ 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