1. Section 7.
Organic Practical [solutions]
2002
Question 2
(a)
(b)
CHEM DIFF: animal saturated (all single bonds) / vegetable unsaturated (double bonds)
WHAT ELSE: anti-bumping granules
WHY REFLUX: because reaction is slow or to complete reaction (6)
to boil (heat) (3) //without losing volatile material (ethanol) (3)
ETHANOL: solvent for lard
WHY REMOVE: easier to isolate soap OR avoid waste of ethanol //
maximize yield
(6, 3)
MINIMUM: to maximise soap precipitating out
BRINE: salt solution
DESCRIBE: filter
PRECAUTION: wash with ice-cold water
(c)
(d)
(e)
2003
X = water OR H2O
Cancelling, including name with formula if either incorrect
Y = calcium dicarbide [CaC2] *Cancelling does not apply if name is correct but formula, though
incorrect, has Ca and C only.
grey lumpy solid
CaC2 + 2H2O = C2H2 + Ca(OH)2
Observation : luminous sooty flame
Equation: C2H2 + 2½O2 → 2CO2 + H2O
FORMULAS (3) BALANCING (3)
Test: reagent Br2 (6) procedure shake with (6) observation decolourised (6)
Question not on syllabus so above answer taken – if answered as asked
equation (3) name of organic product (3) C2H2 + Br2 = C2H2Br2 (3) dibromoethene (3) C2H2 + 2Br2 =
C2H2Br4 (3) tetrabromoethane (3)
oxyacetylene flame (torch – but not blowtorch)
(b)
(c)
(d)
(e)
(f)
(i)
(ii)
(iii)
.
2004
(a)
(b)
(c)
(6)
(3)
(6)
(6)
(4)
(4)
(3)
(6)
(3)
(6)
(18)
(6)
Question 9
(a)
(b)
(3)
(9)
Question 2
(a)
2003
(5)
(6)
(12)
Aldehyde: CH3CH2CHO / C2H5CHO
(In expanded structure, correct bonds must be shown but Hs can be omitted.)
IUPAC: propanal [Accept propan-1-al]
Other: CH3COCH3
Name: propanone / acetone [Accept propan-2-one]
Use: removing nail varnish OR solvent for paint
Which: propanal.
Acid: propanoic acid
Prevents explosions Allow (3) for ‘safety’.
What: mixture of clove oil and water
Describe: cloudy* / milky (not ‘creamy’) / white / emulsion
*Allow only (3) if ‘cloudy’ given with anything other than ‘milky’, ‘white’ or ‘emulsion’
flavouring OR Local anaesthetic
(4)
(4)
(3)
(3)
(6)
(3)
(3)
(6)
(3) +(3)
(6)
(6)
Question 2
FUNCTION: keeps ethanol at end of test tube
IDENTIFY: aluminium oxide [Al2O3]
DESCRIBE: white powder
PRECAUTIONS: Must be matched
first precaution (3) explanation (3); second precaution (3) explanation (3)
keep gas away from flames (3) risk of explosion (3)
safety screen (glasses) (3) risk of explosion (3)
disconnecting tube (3) to prevent suckback (3)
tongs (heat resistant gloves) (3) prevent burns (can be inferred here) (3)
Al2O3
EQUATION: C2H5OH = C2H4 + H2O
(5)
(3)
(3)
(12)
(6)

2. (d)
UNSATD: double or triple bond present
TEST: add bromine water (3) // red [Accept ‘red-brown’ but not ‘brown’] (3) // to colourless OR
decolourises (not ‘goes clear’) (3)
FLAME: yellow OR luminous
EQUATION: C2H4 + 3O2 → 2CO2 + 2H2O
Formulas (3) Balancing (3)
(e)
2004
(a)
(i)
(ii)
(i)
(ii)
(iii)
2005
(a)
(b)
(c)
(d)
(e)
2006
(a)
(b)
(c)
(3)
(6)
Question 3.
(iii)
(iv)
(v)
(b)
(3)
(9)
so that crystals will form on cooling OR to maximise yield
insoluble: filtration of hot solution (3)
remained on filter paper (3)
soluble: filtration of recrystallised benzoic acid OR second filtration (3)
passed through filter paper (funnel) (3)
let solution cool in ice-water [Accept check if melting point is sharp]
leave in warm place
90 %
2.25 × 100 = 90 (3)
2.5
correct diagram with instrument for measuring temperature + one valid label
[e.g. melting point apparatus with thermometer or theile tube containing liquid + thermometer] //
detail of setting up e.g. [sample in melting point tube for melting point apparatus and thiele tube Stated or labelled in diagram] //
method of heating *
[electrical in melting point apparatus - Can be shown on diagram – even if unlabelled] //
heat slowly (gently)* //
* Accept only two from these three points
observe (note) the substance as it is heated* //
note temperature (range) at which it melts //
FOUR POINTS: (6 + 3 x 3)
lower (3)
melting over wider range of temperatures (3)
preservative (E2- -) OR disinfectant
(5)
(12)
(3)
(3)
(3)
(15)
(6)
(3)
Question 2
WHY: ethanal volatile
TWO FEATURES:
first feature(3) explanation(3); second feature(3) explanation (3)
excess ethanol (3) stops at ethanal OR doesn't go to ethanoic acid
immediate distillation (removal) (3) prevents further oxidation (3)
dichromate in funnel (3) small amount of oxidising agent in flask (3)
DESCRIBE: orange solution added to colourless liquid // becomes green (2 × 3)
ACCOUNT: Cr(VI) / Cr2O72-is reduced to Cr(III) / Cr3+ (3)
TEST: mix equal amounts of Fehling's 1 and 2 (3) add ethanal and warm (3)
OBSERVE: brick-red (accept orange/brown) (3) precipitate produced (3)
MASS: 2.97 g [Accept 2.948  3.000 g]
8.94 g sodium dichromate 0.03 mol (3)
0.03 mol dichromate ≡ 0.09 mol ethanal (3)
0.09 mol ethanal 0.09 x 44*  3.96 g ethanal
[*addition must be shown for error to be treated as slip]
75 % yield = 3.96 x 75 = 2.97 g (3) (3)
100
(5)
(12)
(3)
(12)
(12)
Question 2
WHY: to speed up the reaction OR to maximise yield
[Allow ‘to prevent loss of vapour (ethanol, solvent)]
TYPE: base hydrolysis / saponification [Accept substitution]
(5)
(3)
COMPLETE: C17H35COONa + CH2(OH)CH(OH)CH2OH (3)
[Accept without brackets]
BALANCE: 3 C17H35COONa + CH2(OH)CH(OH)CH2OH (3)
WHAT: solvent (3)
WHY: easier to isolate (extract) soap OR to avoid waste of ethanol (3)
(6)
DESCRIBE: diagram showing any two from the box and one correct label
(6)
(6)

3. Bunsen or hot plate & thermometer (positioned correctly) / gentle heat (water bath,) //
still head / distilling flask //
condenser (sloping down, showing inlet & outlet for water) //
collection in vessel (adaptor not required)
[Diagram with any two from the box and no correct label (3)]
[If no marks got for diagram, (3) may be given for ‘heat gently until 20 to 25cm3
ethanol collected’.
To get this (3) there must be a diagram of some sort.]
DESCRIBE:
dissolve residue in minimum of boiling water /water // (3)
pour onto brine // filter // wash with a little ice-water
POUR INTO BRINE (6) ONE OTHER POINT (3)
(e)
(f)
2007
(a)
(b)
(c)
(d)
(e)
(f)
(i)
(ii)
(i)
(ii)
LOCATION: second product: in the filtrate OR Buchner flask
LOCATION: excess sodium hydroxide: in the filtrate OR Buchner flask
OBSERVE: immediate lather
OBSERVE scum OR no lather
(12)
(3)
(3)
(3)
(3)
Question 2
STATE: add slowly // stir after each addition / wait till reaction ceases //
cool reaction vessel
ANY TWO: (2 × 4)
DESCRIBE: orange (3) // to green (3)
EXPLAIN: dichromate (Cr2O72–) reduced to chromium(III) (Cr3+) (3)
PURPOSE: to speed up reaction (oxidation) // to ensure complete oxidation to ethanoic acid //to
heat without loss of vapour (product)
ANY TWO: (2 × 3)
SHOW: mass of ethanol = 8.0 x 0.80 = 6.4 g (3)
moles of ethanol = 6.4 ÷ 46* = 0.139 (0.14) mol (3)
moles dichromate = 29.8 ÷ 298* = 0.1 mol (3) [*addition must be shown for error to be treated as slip.]
0.139 ethanol (x 2/3) ≡ 0.09 mol dichromate OR 0.1 mol dichromate ( x 3/2) ≡ 0.15 mol ethanol (3)
DESCRIBE: isolated by distillation (or distillation diagram)
DESCRIBE: fizzing OR bubbling (3)
WRITE: Na2CO3 + 2CH3COOH → 2CH3COONa + H2O + CO2
FORMULAS (3) BALANCING (3)
(8)
(9)
(6)
(12)
(6)
(6)
2008 Question 2
(a)
(b)
(c)
(d)
(e)
(f)
(g)
DESCRIBE: Paper chromatography [Lid not required in diagram.]
spotting on paper (3) [Some description of application required.]
just [2 cm] above solvent [eluent] (3)
place in suitable container with eluent (3)
solvent moves up (3)
state or show separation of components of mixture (3)
EXPLAIN: diff. adsorbance on mobile and stationary phases
WHAT: do not mix
NAME: name // plant material clove oil // cloves [Correct order not required.]
EXPLAIN: avoids explosion [allow 3 marks for ‘safety’ ]
DESCRIBE: white (creamy) liquid [Allow 3 marks for “ emulsion”.]
NAME: solvent extraction (cyclohexane, ether, etc.) [Allow 3 marks for mention of ‘cyclohexane’
etc. without qualification]
CALCULATE: 1.25 %
0.25/20 (3) ×100 = 1.25 (2)
(15)
(6)
(3)
(2 x 3)
(6)
(6)
(3)
(5)
2009 Question 2
(a)
(b)
(c)
GIVE: aluminium oxide / alumina / Al2O3 (3)
WHAT: white (2)
WRITE: C2H5OH = C2H4 + H2O (3)
TERM: elimination [Accept “dehydration”] [Cancel with second (incorrect) reaction type] (3)
STATE: keep gas from flame / air-tight stopper / secure assembly / don’t use first gas jar //
safety screen / glasses (goggles) / protective clothing / tie hair back //
(5)
(6)
(9)

4. (d)
(e)
(f)
(g)
before heat removed take tube from water / disconnect tube / dismantle apparatus //
use tongs / gloves //
avoid inhaling glass wool / wear mask ANY THREE: (3 x 3)
GIVE: calcium(II) dicarbide / calcium carbide / carbide / CaC2 (3)
DESCRIBE: black / dark / grey / off-white / grey black / brown-grey / dirty solid (3)
[“Give” & “Describe” not linked]
WHAT: double (triple, multiple) carbon-to-carbon bond present / undergoes addition (3)
TEST: add bromine water / bromine soln. / Br2 / acidified KMnO4 soln (3)
decolourises / changes to colourless (not ‘clear’) (3) [The two (3)s are not linked]
WHAT: ethene less (ethyne more) luminous (smoky, sooty) (3)
[Allow “ethene has yellow flame whereas ethyne’s is sooty (smoky)”]
[Accept ‘ethyne produces soot’; otherwise comparing ethyne with ethene is required and cannot be
assumed.]
WRITE: C2H4 + 3O2 = 2CO2 + 2H2O or C2H2 + 2 ½ O2 = 2CO2 + H2O or
2C2H2 + 5O2 = 4CO2 + 2H2O
FORMULAS (3) BALANCING (3)
GIVE: (i) ethene: manufacture of polythene {poly(ethene), plastic, polymer)} / make ethane-1,2diol (ethylene glycol, antifreeze) / make polyester (terylene) / make chloroethene (vinyl
chloride) / make PVC {polyvinylchloride, poly(chloroethene)} / make ethanol / make
phenylethene (styrene) / make poly(phenylethene) {polystyrene} / ripening fruit (3)
[Allow “growth hormone”, “growth promoter”]
(ii) ethyne: oxyacetylene flame (torch – not blowtorch) / cutting metals / welding metals /
make ethanal (propanone, propan-2-ol, polymers, plastics, pesticides) / fuel for lamps [not
‘fuel’ on its own] (3)
[Do not accept general terms e.g. “medicine”, agriculture”,” industry”, in both above answers, but do
not cancel them with an acceptable use.]
(6)
(9)
(9)
(6)