DISTILLATION OF PETROLEUM

Transcription

1 QUESTIONSHEET 1 DISTILLATION OF PETROLEUM a) (i) Mixture of alkanes with a wide range of M r Middle East crude has a relatively high proportion of alkanes of high M r b) (i) Mixture of alkanes / compounds of similar boiling point Boiling point c) Sketch to show: furnace for partial vaporisation of crude oil fractionating column any indication of trays and bubble caps injection of feedstock (superheated) steam injected at base of column Maximum 3 marks d) (i) ool / 110 º at top to hot / 340 º at bottom Petroleum gases from top of column Light gasoline / petrol from top or near top Then, in decreasing order: heavy gasoline / naphtha kerosene / paraffin diesel fuel / DERV lubricating oil Maximum 4 marks e) Material Bitumen Use Road surfacing / for making fuel oil f) Industrial operation is continuous Laboratory operation is a batch process Half marks if shown at incorrect levels

2 QUESTIONSHEET 2 RAKING a) (i) Insufficiently volatile / does not fully vaporise in the cylinder (H 2 ) 8 (H 2 ) 6 + H 2 = H 2 (H 2 ) 8 (H 2 ) 5 + H = H 2 (iii) Lower alkanes are useful as petrol Lower alkenes can be polymerised Or one example of polymerisation Alkenes are used as feedstock for the petrochemical industry Or one example of this b) Thermal cracking atalytic cracking High temperature (½) High pressure (½) High temperature (½) Slight pressure (½) Zeolite / alumino-silicate catalyst Type of bond breaking Homolytic Heterolytic Type of reaction intermediate Free radicals arbonium ions / carbocations Principal products Alkenes Motor fuels / arenes c) Reaction occurs on the surface of a catalyst With prolonged use the surface becomes coated / inefficient / will not properly adsorb reactants so the catalyst must be replaced Maximum 2 marks

3 QUESTIONSHEET 3 FUELS a) (i) Methane -882/16 = kj g -1 Octane -5512/114 = kj g -1 Volume problem if H 4 is gaseous ost / weight / escape problem if H 4 is liquid Transfer / refuelling problem for gaseous fuels Maximum 2 marks b) Disadvantage : too great a volume/bulky or usable volume would require high pressure so eg reinforced dense containers Advantage : non-polluting/only forms water/renewable c) (i) Benzene arcinogenic / causes cancer Tetraethyllead Exhaust emissions are poisonous / cause brain damage in children arbon monoxide O (iii) arbon dioxide Global warming Nitrogen dioxide Acid rain d) (i) ompression ignition / no spark plug Higher alkanes / higher M r / higher b.p. / greater chain length (iii) Particulate carbon e) neutral : absorbs as much carbon dioxide during growth as during combustion footprint : only gives out carbon dioxide/net producer of carbon dioxide

4 QUESTIONSHEET 4 EPOXYETHANE AND ETHANE-1,2-DIOL a) (i) 2H 2 = H 2 (g) + O 2 (g) 2H 2 H 2 (g) Silver (iii) To relieve the pressure / by Le hatelier s principle equilibrium is disturbed to the side with fewer gas molecules (iv) Risk of explosive oxidation if too much ethene is present b) (i) The O bond angle is only 60º the ring is strained / strain is relieved when the ring opens up H 2 H 2 OH O + OH H 2 H 2 O O (iii) H 2O + H3 O(H 2 ) OH H O(H ) O(H ) OH H 2 c) The molecule hydrogen bonds with water through two OH groups there is little loss through vaporisation d) (i) A chemical reaction in which two reactants undergo addition with subsequent elimination of a small molecule, such as H 2 O O O H O O H (iii) Instead of one molecule of acid reacting with one molecule of the diol, one acid molecule reacts with the OH groups of two diol molecules Or explained by formulae e) Hydraulic fluid / brake fluid

5 QUESTIONSHEET 5 ADDITION POLYMERS a) Monomer A simple molecule which is used in forming a polymer Addition polymer A large molecule formed by combination of unsaturated molecules without loss of atoms b) (i) LDPE random overlap of chains with chain-branching HDPE relatively parallel chains with little chain-branching c) (i) Greater impact strength Higher melting-point Increased transparency Softens less easily when hot any two = (2) H 2 OO H (2) deduct 1 mark per error - bonds must project through brackets n d) PV /polyvinyl chloride/poly(chloroethene) e) Polar -l bonds Gives dipole attraction between chains Stronger than van der Waals attraction with poly(ethane) any 3 f) Poly(ethene) OH - nucleophile attacks polar -l bond Poly(ethene) non-polar g) ombustion gives carcinogenic dioxins/hl Do not biodegrade

6 QUESTIONSHEET 6 HALOALKANES AS SYNTHETI INTERMEDIATES a) B = Ethene = Ethyl hydrogen sulfate D = Ethanol E = Ethanoic acid F = Propanenitrile G = Propanoic acid b) 2 H 6 SO 4 oncentrated H 2 SO 4 Water Room temp. / Warm / B 2 H 4 oncentrated H 2 SO D 2 H 6 O Alcoholic KOH / NaOH Aqueous NaOH / KOH Heat / boil Heat / boil under reflux A 2 Br Na 2 r 2 O 7 + dil. H 2 SO 4 Heat / boil under reflux KN / NaN Heat / boil in aq. ethanol E 2 H 4 O 2 Dilute H 2 SO 4 / Hl(aq) F 3 N G 3 H 6 O 2 Heat / boil under reflux

7 QUESTIONSHEET 7 Fs a) (i) hlorofluorocarbon l F l F (Accept Hl 2 HF 2 ) H H (iii) In refrigerators / air conditioning units In the manufacture of expanded polystyrene Sprays for muscular sports injuries As cleaners Maximum 2 marks b) (i) An atom or group of atoms with an unpaired electron F bond is stronger than the l bond because the F atom is smaller than the l atom / the F bond is shorter than the l bond (iii) Reaction 1 l + O 3 lo + O 2 Reaction 2 lo + O l + O 2 (iv) The l free radical is catalyst and is not used up The l free radical which is used in Reaction 1 reappears as a product in Reaction 2 Because l free radicals are regenerated, they are available to bring about further change Maximum 2 marks (v) At high altitudes the concentrations of the gaseous reactants are very low c) (i) Greater intensity of ultraviolet light reaching the Earth s surface can lead to skin cancer ontribute to the greenhouse effect (iii) Butane / ammonia / dinitrogen monoxide

8 QUESTIONSHEET 8 USES OF OTHER ORGANI HALOGENOOMPOUNDS a) (i) Paint / electrodeposited metals will not adhere to a greasy surface Precaution Efficient fume extraction Reason Vapour is highly toxic / causes liver damage (iii) Dry cleaning b) (i) Durability / resistance to weathering Low maintenance costs / does not need painting Fire resistance Name Poly(tetrafluoroethene) / PTFE Use Non-stick pans c) (i) Slow to break down in the environment / effective for a long time an enter the food chain d) (i) Forms a blanket of non-flammable vapour which excludes air / oxygen Foam extinguishers may cause a short circuit / BF cannot do so

9 QUESTIONSHEET 9 FERMENTATION a) (i) Glucose / fructose In the absence of air / oxygen (iii) 6 H 12 O OH + 2O 2 (2) Award for reactant and for products if balance is correct. (iv) atalyst b) (i) Flexible tube Gas syringe Thermostaically controlled water bath Sugar solution + yeast Rate Temperature (iii) Rate of reaction / fermentation increases with temperature until higher temperatures denature the enzyme 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 Synthetic ethanol contains fewer impurities

10 QUESTIONSHEET 10 SYNTHETI ETHANOL PROESS a) (i) H 2 = H 2 (g) + H 2 O(g) ¾ H 2 OH(g) Electrophilic (½) addition (½) b) (i) arbocation / carbonium ion Arrow bottom left (should be encircled) should point from the bond to the O atom c) Advantage Increased rate of reaction / attaining equilibrium Disadvantage Lower yield of ethanol at equilibrium d) (i) Higher yield of ethanol at equilibrium Equilibrium is disturbed to the side with fewer gas molecules so as to relieve the pressure / in accordance with Le hatelier s principle Higher power costs for the compressor High cost of constructing / maintaining thick-walled pressure vessels e) (i) So that it presents a larger surface area to the reactants No effect f) ool / condense to give aqueous ethanol oncentrate by fractional distillation Add methanol

11 QUESTIONSHEET 11 ETHANOL AS A FUEL a) (i) 8 H 18 (l) + 12½O 2 (g) 8O 2 (g) + 9H 2 O(l) 2 OH(l) + 3O 2 (g) 2O 2 (g) + 3H 2 O(l) b) (i) m ( 8 H 18 ) = 1000 x 0.72 = 720 g (½) n ( 8 H 18 ) = 720/114 = mol (½) enthalpy change = x ,800 kj m ( 2 OH) = 1000 x 0.79 = 790 g (½) n ( 2 OH) = 790/46 = mol (½) enthalpy change = x ,500 kj mol -1 c) (i) mol 8 H x 8 = mol O 2 m (O 2 ) = x 44 = 2223 g O mol 2 OH x 2 = mol O 2 m (O 2 ) = x 44 = 1511 g O 2 d) (i) 2223/34800 = g kj /23500 = g kj -1 omment Similar masses of O 2 in both cases, therefore a similar impact on the environment e) Ethene originates from crude oil / fossil fuel / petroleum on combustion ethanol releases additional O 2 to the atmosphere Using ethanol made by fermentation recycles O 2 (No marks for greenhouse effect unless related to O 2 in the atmosphere)

12 QUESTIONSHEET 12 DISPOSAL OF ORGANI WASTE a) (i) A huge range of plastics is in common use Separation is virtually impossible Paper can be pulped Vegetable waste can be composted b) Detrimental to the environment because of the large quantity of waste involved Toxic substances from industrial waste may contaminate surrounding land / enter the water table Microbiological reactions in the waste may produce toxic substances Maximum 2 marks c) Domestic heating projects Generating electricity, using a steam turbine d) (i) hlorinated materials produce toxic compounds / dioxins Incomplete combustion leading to carbon monoxide / soot e) Sulfur-containing materials produce SO 2 / SO 3 / oxides of sulfur Nitrogen-containing materials produce NO 2 / oxides of nitrogen These gases cause acid rain f) Most noxious gases / named examples are acidic they can be removed by passing over a base / scrubbing with an alkaline solution