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NOVEMBER 2001
ADVANCED SUBSIDIARY LEVEL
MARK SCHEME
MAXIMUM MARK : 60
SYLLABUS/COMPONENT : 8701/2
CHEMISTRY
(Structured Questions)
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Page 1 of 3
Mark Scheme
AS Level Examinations – June 2001
Question
Number
Mark Scheme Details
1 (a)
Mg
Mg
(b) (i)
(ii)
(iii)
(c) (i)
(ii)
2 (a) (i)
(ii)
2+
2s2
2p6
2
2
6
2s
2
O
1s
O2-
1s2
¡
l
¡
l
l
¡
l
2p
2
2p4
2s2
2p6
2s
3s2
(1)
(1)
[2]
¡
l is Mg
¡
l
¡ is O
l
¡
2+
regular (1)
2-
[2]
cations surrounded by anions etc. (1)
Two physical properties
insulator
ions unable to move
high m.p./b.p. forces between doubly charged ions are strong
insoluble in water
conducts when molten
(1) for each
Furnace linings, electrical insulators, spark plugs, ceramics
any two
CO (1) and water vapour (1)
[or from equations]
CaO + H2O à Ca(OH)2 (1)
Ca(OH)2 + CO2 à CaCO3 + H2O OR CaO + CO2 à CaCO3 (1) max 3
[3]
[Total:
10]
Ea uncat
activation energy
mentioned (1)
two Ea peaks (1)
Ea cat
products
reactants
(1)
+14 Kcal mol-1 (1)
[5]
reaction pathway
(ii)
Kc =
[ester][wa ter]
[acid][alcohol]
(1)
Since same number of terms in expression, top & bottom
or equivalent (1)
(c) (i)
(ii)
[2]
[1]
Rate of forward reaction is equal to rate of backward or equivalent. (1)
energy
(b) (i)
Paper
2
Part
Mark
1s2
1s
Syllabus
8701
[2]
ethanol = ethanoic acid = 0.43 (1)
ethyl ethanoate = 0.57 (1)
water = 1.57 (1)
Kc =
0.57 x 1.57
0.43 x 0.43
= 4.84 (1)
[4]
[marked consequentially from (i)]
[Total:
11]
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Page 2 of 3
3 (a)
(b)
(c) (i)
(ii)
(iii)
(iv)
(d) (i)
(ii)
(iii)
Mark Scheme
IGCSE Examinations – November 2001
Syllabus
8701
red / brown liquid / vapour (1)
Stronger van der Waals’ forces between molecules (1)
since bromine is a bigger molecule / more electrons than chlorine (1)
and has more induced dipoles on its surface (1)
Max (2)
2P + 5Cl2 à 2PCl5 (1)
PCl5 + 4H2O à H3PO4 + 5HCl (1)
NaCl + AgNO3 à AgCl ↓ + NaNO3
OR Cl - (aq) + Ag+ (aq) à AgCl (s) (1)
(1)
AgCl + 2NH3 à Ag(NH3)2+(aq) + Cl- OR to Ag(NH3)2Cl
CH2=CH2 + Br2 à CH2BrCH2Br (1)
Electrophilic addition (1)
Electron-rich double bond attracts Br2 which is then polarised
CH2
Br
CH2
d+
Br
d -
(1)
(b) (i)
(ii)
(c) (i)
(ii)
(iii)
(d)
(e) (i)
(ii)
zero
-3
NO2NO3-
(1)
[4]
[5]
+3
+5
H Å
xx
H x N ● H
● x● x
H
charge (1)
tetrahedral, 109 or 109 1 º
[2]
[2]
[3]
[1]
To include dative bond
[2]
(1)
[Total:
CH3(CH2)9CHBrCH2Br (1)
CH3(CH2)9CHBrCH3 (1)
CH3(CH2)9CO2H (1)
CH3(CH2)9CH(OH)CH3 (1)
12]
(1)
The triple bond (high energy) needs to be broken (1)
gives NH4+ directly / gives soluble N to soil (1)
6.3 x 10-9 mol dm-3 (1)
Since H+ is a product, and this is removed (1)
lime / a base / ammonia (1)
Waterlogged soils will contain very little oxygen / will discourage nitrifying
bacteria
(1)
2
5 (a) (i)
(ii)
(iii)
(iv)
[2]
(1)
[Total:
N2
NH4+
[1]
intermediate CH2CH2Br+ (1)
Final addition of Br-
4 (a)
Paper
2
max 10]
[4]
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Page 3 of 3
(b) (i)
(ii)
Mark Scheme
AS Level Examinations – June 2001
optical isomerism (1)
CH3(CH2)9
C
Syllabus
8701
Paper
2
CH3(CH2)9
C
H
H
CH3
Br
(1) each
(c)
CH3(CH2)8
H
C
CH3(CH2)8
C
CH3
C
H
CH3
[3]
CH3
Br
H
C
H
cis
trans
[2]
(1) each
[Total:
6
A Only alcohol
+
2-
Not H /Cr2O7
sodium (1) – bubbles of gas / H2 (1)
OR PCl5 (1) misty fumes (1)
OR carboxylic acid + catalyst (1) smell of
ester (1)
+
9]
[2]
-
or H /MnO4
B Only ketone
C alkene and aldehyde
D aldehyde only
DNP reagent gives red precipitate (1)
does not give Tollens or Fehlings
OR H+/Cr2O72- tests (1)
[2]
decolourises Br2 (water) (1)
red/brown ppt with Benedicts or Fehlings
OR Ag mirror – Tollens (1)
DNP test (1) if not used elsewhere
[2]
DNP gives red ppt (1)
Benedicts/Tollens/Fehlings positive (1)
(as C)
[Total:
[2]
8]