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Unit 2 Fuels

Unit 2 Fuels. HIGHER CHEMISTRY REVISION. Unit 2:- Fuels. Unleaded petrol uses hydrocarbons with a high degree of molecular branching in order to improve the efficiency of burning. The structure of one such hydrocarbon is shown.

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Unit 2 Fuels

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  1. Unit 2Fuels

  2. HIGHER CHEMISTRY REVISION. Unit 2:- Fuels • Unleaded petrol uses hydrocarbons with a high degree of molecular branching in order to improve the efficiency of burning. • The structure of one such hydrocarbon is shown. •    (a) Give the systematic name for this hydrocarbon. • (b) Name one other type of hydrocarbon that is used in petrol • for the same reason. • 2,3,4-trimethylpentane. • (b) Cyclic hydrocarbons or aromatic hydrocarbons.

  3. CH3 • CH3 C=CHCH3 • (b) Catalyst. • (c) 2-methylbutaneis a branched chain molecule which is not as likely to • ignite prematurely as the straight chain pentane molecule in a car engine. 2. Mordenite is a porous material with a surface area of over 500 m2 g-1. It is used in an isomerisation reaction, part of a sequence which converts pentane into 2-methylbutane for blending into petrol. pentane pent-2-ene 2-methylbut-2-ene 2-methylbutane (a) Draw a structural formula for 2-methylbut-2-ene. (b) What role does mordenite play in the isomerisation reaction? (c) Why is 2-methylbutane a more suitable component than pentane when used in unleaded petrol? Higher Chemistry

  4. 3. Petrol is produced by the reforming of a fraction obtained from crude oil. One such reforming reaction is:- CH3–CH2–CH2–CH2–CH2–CH2–CH2–CH3 CH3–C–CH2–CH2–CH3 octane Compound A (a) Which crude oil fraction is reformed to make petrol? (b) Give the systematic name for compound A. (c) If petrol burned in a car engine contains straight-chain alkanes. like octane, a process called ‘knocking’ takes place. Why does the presence of straight-chain alkanes result in ‘knocking’? CH3 CH3 • Naphtha. • 2,2-dimethylpentane. • Straight chain compound tend to undergo premature ignition in a petrol engine.

  5. 4. Carbon monoxide and oxides of nitrogen are pollutants present • in the exhaust gases from petrol engines. • Explain how • (i) carbon monoxide forms in a petrol engine. • (ii) oxides of nitrogen form in a petrol engine. • A catalytic converter fitted to a car exhaust will turn these pollutant gases into less harmful gases. • Name the gases formed from the • (i) carbon monoxide. • (ii) oxides of nitrogen. • (c) Name a metal used as a catalyst in a catalytic converter. • (a) (i) Incomplete combustion of the hydrocarbon fuel produces • carbon monoxide. • (ii) The high energy spark that ignites the petrol and • mixture provides enough energy for nitrogen and oxygen • (from air) to combine to form oxides of nitrogen. • (i) carbon dioxide. • (ii) nitrogen and oxygen. • (c) Platinum.

  6. 5. Under anaerobic conditions, carbohydrates, like glucose, can be used to produce biogas. The main constituent of biogas is methane which is a useful fuel. State one advantage of using biogas as a fuel rather than natural gas. Biogas is formed from a renewable source unlike natural gas which is in finite supply.

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