questionsheet 1 distillation of petroleum · distillation of petroleum a) (i) ... as level topic 15...

$: QUESTIONSHEET 1 DISTILLATION OF PETROLEUM · DISTILLATION OF PETROLEUM a) (i) ... AS Level TOPIC 15 ANSWERS & MARK SCHEMES ... Concentrate by fractional distillation (1) Add methanol$
TOPIC 15 ANSWERS & MARK SCHEMESAS Level

DISTILLATION OF PETROLEUM

a) (i) Mixture of alkanes with a wide range of Mr (1)

(ii) Middle East crude has a relatively high proportion of alkanes of high Mr (1)

b) (i) Mixture of alkanes / compounds (1)of similar boiling point (1)

(ii) Boiling point (1)

c) Sketch to show:furnace for partial vaporisation of crude oil (1)fractionating column (1)any indication of trays and bubble caps (1)injection of feedstock (1)(superheated) steam injected at base of column (1)Maximum 3 marks

d) (i) Cool / 110 ºC at top to hot / 340 ºC at bottom (1)

(ii) Petroleum gases from top of column (1)Light gasoline / petrol from top or near top (1)Then, in decreasing order:heavy gasoline / naphtha (1)kerosene / paraffin (1)diesel fuel / DERV (1)lubricating oil (1)Maximum 4 marks

e) Material Bitumen (1)

Use Road surfacing / for making fuel oil (1)

f) Industrial operation is continuous (1)Laboratory operation is a batch process (1)

Half marks if shown atincorrect levels

QUESTIONSHEET 1


CRACKING

a) (i) Insufficiently volatile / does not fully vaporise in the cylinder (1)

(ii) CH3(CH

2)

8CH

3 → CH

3(CH

2)

6CH

3 + CH

2 = CH

2 (1)

CH3(CH

2)

8CH

3 → CH

3(CH

2)

5CH

3 + CH

3CH = CH

2 (1)

(iii) Lower alkanes are useful as petrol (1)Lower alkenes can be polymerised (1)Or one example of polymerisation (1)Alkenes are used as feedstock for the petrochemical industry (1)Or one example of this (1)

b)

c) Reaction occurs on the surface of a catalyst (1)With prolonged use the surface becomes coated / inefficient / will not properly adsorb reactants (1)so the catalyst must be replaced (1)Maximum 2 marks

Conditions

Type of bond breaking

Type of reaction intermediate

Principal products

Catalytic crackingThermal cracking

High temperature (½)High pressure (½)

Homolytic (1)

Free radicals (1)

Alkenes (1)

High temperature (½)Slight pressure (½)Zeolite / alumino-silicate catalyst (1)

Heterolytic (1)

Carbonium ions / carbocations (1)

Motor fuels / arenes (1)

QUESTIONSHEET 2


FUELS

a) (i) Methane -882/16 = - 55.1 kJ g-1 (1)Octane -5512/114 = - 48.4 kJ g-1 (1)

(ii) Volume problem if CH4 is gaseous (1)

Cost / weight / escape problem if CH4 is liquid (1)

Transfer / refuelling problem for gaseous fuels (1)Maximum 2 marks

b) Disadvantage : too great a volume/bulky or usable volume would require high pressure so eg reinforceddense containers (1)

Advantage : non-polluting/only forms water/renewable (1)

c) (i) Benzene Carcinogenic / causes cancer (1)

Tetraethyllead Exhaust emissions are poisonous / cause brain damage in children (1)

(ii) Carbon monoxide (1) CO (1)

(iii) Carbon dioxide (1) Global warming (1)Nitrogen dioxide (1) Acid rain (1)

d) (i) Compression ignition / no spark plug (1)

(ii) Higher alkanes / higher Mr / higher b.p. / greater chain length (1)

(iii) Particulate carbon (1)

e) C neutral : absorbs as much carbon dioxide during growth as during combustion (1) C footprint : only gives out carbon dioxide/net producer of carbon dioxide (1)

QUESTIONSHEET 3


EPOXYETHANE AND ETHANE-1,2-DIOL

O

(1)

a) (i) 2CH2 = CH

2(g) + O

2(g) → 2CH

2 – CH

2(g) (1)

(ii) Silver (1)

(iii) To relieve the pressure / by Le Chatelier’s principle (1)equilibrium is disturbed to the side with fewer gas molecules (1)

(iv) Risk of explosive oxidation if too much ethene is present (1)

b) (i) The C ⎯ O ⎯ C bond angle is only 60º (1)∴ the ring is strained / strain is relieved when the ring opens up (1)

(ii) CH2

CH2OH

O + CH3OH → (1)

CH2 CH

2OCH

3

(iii) CH2

O + CH3O(CH

2)

2OH → CH

3O(CH

2)

2O(CH

2)

2OH (1)

CH2

c) The molecule hydrogen bonds with water through two OH groups (1)∴ there is little loss through vaporisation (1)

d) (i) A chemical reaction in which two reactants undergo addition (1)with subsequent elimination of a small molecule, such as H

2O (1)

(ii)

(iii) Instead of one molecule of acid reacting with one molecule of the diol, one acid molecule reacts with the –OHgroups of two diol molecules (1)Or explained by formulae (1)

e) Hydraulic fluid / brake fluid (1)

C

CO

O

O

O H

H

QUESTIONSHEET 4


ADDITION POLYMERS

QUESTIONSHEET 5

a) Monomer A simple molecule which is used in forming a polymer (1)Addition polymer A large molecule formed by combination of unsaturated molecules without loss of atoms (1)

b) (i) LDPE random overlap of chains with chain-branching (1)HDPE relatively parallel chains with little chain-branching (1)

(ii) Greater impact strengthHigher melting-pointIncreased transparencySoftens less easily when hot any two = (2)

c) (i)

(ii)

CH3

CCOOCH3

CH2

(1)

C

CH3 nCH3

C

H CH3 (2) deduct 1 mark per error -bonds must project through brackets

d) PVC /polyvinyl chloride/poly(chloroethene) (1)

e) Polar C-Cl bonds (1)Gives dipole attraction between chains (1)Stronger than (1) van der Waals attraction with poly(ethane) (1) any 3

f) Poly(ethene) (1)OH- nucleophile attacks (1) polar C-Cl bond (1)Poly(ethene) non-polar (1)

g) Combustion gives carcinogenic dioxins/HCl (1)Do not biodegrade (1)


a) B = Ethene (1)C = Ethyl hydrogen sulfate (1)D = Ethanol (1)E = Ethanoic acid (1)F = Propanenitrile (1)G = Propanoic acid (1)

b)

HALOALKANES AS SYNTHETIC INTERMEDIATES

C C2H

6SO

4

Reagent(s)

Conditions

Reagent(s)

Conditions

Reagent(s)

Conditions

Concentrated H2SO4 (1)

170 - 180 0C

Concentrated H2SO4

Room temp. / 10-30 0C (1)

(1)

(1)

Water

Warm / 30 - 40 0C

Alcoholic KOH / NaOH

Heat / boil

(1)

(1)

Na2Cr2O7 + dil. H2SO4

(1)

Heat / boil under reflux (1)

Heat / boil under reflux

(1)

(1)

KCN / NaCN

Heat / boil in aq. ethanol

(1)

(1)

Dilute H2SO4 / HCl(aq)

Heat / boil under reflux

Reagent(s)

Conditions

Reagent(s)

Conditions

D C2H

6OB C

2H

4

Reagent(s)

Conditions

A C2H

5Br

Reagent(s)

Conditions

Reagent(s)

ConditionsE C

2H

4O

2

F C3H

5N G C

3H

6O

2

Aqueous NaOH / KOH

(1)

(1)

(1)

(1)

QUESTIONSHEET 6


CFCs

a) (i) Chlorofluorocarbon (1)

(ii)

(iii) In refrigerators / air conditioning units (1)In the manufacture of expanded polystyrene (1)Sprays for muscular sports injuries (1)As cleaners (1)Maximum 2 marks

b) (i) An atom or group of atoms with an unpaired electron (1)

(ii) C⎯F bond is stronger than the C⎯Cl bond (1)because the F atom is smaller than the Cl atom / the C⎯F bond is shorter than the C ⎯Cl bond (1)

(iii) Reaction 1 ·Cl + O3 → ·ClO + O

2 (1)

Reaction 2 ·ClO + O → ·Cl + O2 (1)

(iv) The Cl free radical is catalyst (1)and is not used up (1)The Cl free radical which is used in Reaction 1 reappears as a product in Reaction 2 (1)Because Cl free radicals are regenerated, they are available to bring about further change (1)Maximum 2 marks

(v) At high altitudes the concentrations of the gaseous reactants are very low (1)

c) (i) Greater intensity of ultraviolet light reaching the Earth’s surface (1)can lead to skin cancer (1)

(ii) Contribute to the greenhouse effect (1)

(iii) Butane / ammonia / dinitrogen monoxide (1)

C C

H

Cl

FCl

H

F

(1) (Accept CHCl2CHF2)

QUESTIONSHEET 7


USES OF OTHER ORGANIC HALOGENOCOMPOUNDS

a) (i) Paint / electrodeposited metals will not adhere to a greasy surface (1)

(ii) Precaution Efficient fume extraction (1)Reason Vapour is highly toxic / causes liver damage (1)

(iii) Dry cleaning (1)

b) (i) Durability / resistance to weathering (1)Low maintenance costs / does not need painting (1)Fire resistance (1)

(ii) Name Poly(tetrafluoroethene) / PTFE (1)Use Non-stick pans (1)

c) (i) Slow to break down in the environment / effective for a long time (1)

(ii) Can enter the food chain (1)

d) (i) Forms a blanket of non-flammable vapour (1)which excludes air / oxygen (1)

(ii) Foam extinguishers may cause a short circuit / BCF cannot do so (1)

QUESTIONSHEET 8


FERMENTATION

a) (i) Glucose / fructose (1)

(ii) In the absence of air / oxygen (1)

(iii) C6H

12O

6 → 2C

2H

5OH + 2CO

2 (2)

Award (1) for reactant and (1) for products if balance is correct.

(iv) Catalyst (1)

b) (i)

(iii) Rate of reaction / fermentation increases with temperature (1)until higher temperatures denature the enzyme (1)

c) Brazil has a warm climate (½)with a high intensity of sunlight for long periods (½)Therefore sugar cane (accept ‘plants’) grows quickly (½)Brazil has little reserves of mineral oil (½)and cannot afford using scarce foreign currency to purchase oil (½)Maximum 2 marks

d) Rapid (1)Synthetic ethanol contains fewer impurities (1)

(ii)

(1)

QUESTIONSHEET 9

Rate

Temperature

Flexible tube Gas syringe (1)

Sugar solution + yeast

Thermostaically controlled water bath (1)


SYNTHETIC ETHANOL PROCESS

a) (i) CH2 = CH

2(g) + H

2O(g) ¾ CH

3CH

2OH(g) (1)

(ii) Electrophilic (½) addition (½)

b) (i) Carbocation / carbonium ion (1)

(ii) Arrow bottom left (should be encircled) should point from the bond to the O atom (1)

c) Advantage Increased rate of reaction / attaining equilibrium (1)Disadvantage Lower yield of ethanol at equilibrium (1)

d) (i) Higher yield of ethanol at equilibrium (1)Equilibrium is disturbed to the side with fewer gas molecules (1)so as to relieve the pressure / in accordance with Le Chatelier’s principle (1)

(ii) Higher power costs for the compressor (1)High cost of constructing / maintaining thick-walled pressure vessels (1)

e) (i) So that it presents a larger surface area to the reactants (1)

(ii) No effect (1)

f) Cool / condense to give aqueous ethanol (1)Concentrate by fractional distillation (1)Add methanol (1)

QUESTIONSHEET 10


ETHANOL AS A FUEL

a) (i) C8H

18(l) + 12½O

2(g) → 8CO

2(g) + 9H

2O(l) (1)

(ii) C2H

5OH(l) + 3O

2(g) → 2CO

2(g) + 3H

2O(l) (1)

b) (i) m (C8H

18) = 1000 x 0.72 = 720 g (½)

∴ n (C8H

18) = 720/114 = 6.316 mol (½)

∴ enthalpy change = -5512 x 6.316 ≈ 34,800 kJ (1)

(ii) m (C2H

5OH) = 1000 x 0.79 = 790 g (½)

∴ n (C2H

5OH) = 790/46 = 17.17 mol (½)

∴enthalpy change = -1371 x 17.17 ≈ 23,500 kJ mol-1 (1)

c) (i) 6.316 mol C8H

18 → 6.316 x 8 = 50.53 mol CO

2 (1)

∴ m (CO2) = 50.53 x 44 = 2223 g CO

2 (1)

(ii) 17.17 mol C2H

5OH → 17.17 x 2 = 34.34 mol CO

2 (1)

∴ m (CO2) = 34.34 x 44 = 1511 g CO

2 (1)

d) (i) 2223/34800 = 0.0639 g kJ-1 (1)

(ii) 1511/23500 = 0.0643 g kJ-1 (1)

Comment Similar masses of CO2 in both cases, therefore a similar impact on the environment (1)

e) Ethene originates from crude oil / fossil fuel / petroleum (1)∴ on combustion ethanol releases additional CO

2 to the atmosphere (1)

Using ethanol made by fermentation recycles CO2 (1)

(No marks for ‘greenhouse effect’ unless related to CO2 in the atmosphere)

QUESTIONSHEET 11


DISPOSAL OF ORGANIC WASTE

a) (i) A huge range of plastics is in common use (1)Separation is virtually impossible (1)

(ii) Paper can be pulped (1)Vegetable waste can be composted (1)

b) Detrimental to the environment because of the large quantity of waste involved (1)Toxic substances from industrial waste may contaminate surrounding land / enter the water table (1)Microbiological reactions in the waste may produce toxic substances (1)Maximum 2 marks

c) Domestic heating projects (1)Generating electricity, using a steam turbine (1)

d) (i) Chlorinated materials (1)produce toxic compounds / dioxins (1)

(ii) Incomplete combustion (1)leading to carbon monoxide / soot (1)

e) Sulfur-containing materials produce SO2 / SO

3 / oxides of sulfur (1)

Nitrogen-containing materials produce NO2 / oxides of nitrogen (1)

These gases cause acid rain (1)

f) Most noxious gases / named examples are acidic (1)∴ they can be removed by passing over a base / scrubbing with an alkaline solution (1)

QUESTIONSHEET 12

questionsheet 1 distillation of petroleum · distillation of petroleum a) (i) ... as level topic 15...

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