• Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

Petrol - In its crude state, petroleum is a virtually useless material.

Extracts from this document...


Petrol In its crude state, petroleum is a virtually useless material. However when refined, the hydrocarbons it contains supply almost half the world's current energy needs and are the starting chemicals from which about 90% of the worlds organic chemicals are made. Fractional distillation is the process by which the different fractions in crude petroleum are separated according to their boiling points. One of the fractions obtained is naphtha. Further fractionation of naphtha yields petrol (C - C alkanes). In the internal combustion engine, a piston compresses a mixture of air and petrol vapour. At the point of maximum compression, an electrical spark ignites the petrol/air mixture and rapid combustion occurs. A typical reaction would be the combustion of octane: The hot gaseous products expand against the piston and force it downwards. This mechanical energy is transmitted to the drive wheels of the car, enabling it to move. ...read more.


To determine the octane rating of petrol a sample is taken and its anti-knock performance is compared to that of 2,2,4-trimethylpentane/heptane mixtures. There are 2 ways of increasing the petrol's octane number. The anti-knock agent tetraethyl lead can be added. This breaks up during combustion to form tiny lead(IV)oxide particles which ensure even combustion of the fuel at a moderate rate. To prevent a build up of lead(IV)oxide in the cylinder, a small amount of 1,2-dibromoethane is added to the petrol. This reacts with the residual lead oxide to produce lead bromide, a fairly volatile compound. As it is volatile, lead bromide passes with the other exhaust gases into the atmosphere. There is a danger with lead compounds as they are very toxic and lead to atmospheric pollution. Inhalation of lead-polluted air causes a build up of lead in the blood, and this is thought to impair the brains activity. ...read more.


Another product of incomplete combustion is carbon monoxide, a very poisonous gas which bonds irreversibly with the haemoglobin in the blood, thereby blocking the uptake of oxygen and preventing its transport around the body. In an enclosed space, exposure to carbon monoxide can be fatal. Car exhaust fumes may contain up to 2% by volume of carbon monoxide, together with other pollutants. There are other concerns over the use of petrol to fuel our transport systems. Unburnt hydrocarbons, escape in exhaust fumes, and from petrol tanks when they are being filled at petrol stations. These may contain benzene, which is a known carcinogen. The oxides of nitrogen are present in the exhaust gases. These cause several pollution problems once they enter the atmosphere. One of these is acid rain. In the presence of sunlight the nitrogen dioxide present in exhaust gases also reacts with the unburnt hydrocarbons to form photochemical smog. The smog contains a variety of chemicals that are irritants, and may be responsible for the increase in asthma attacks during the summer. ...read more.

The above preview is unformatted text

This student written piece of work is one of many that can be found in our GCSE Organic Chemistry section.

Found what you're looking for?

  • Start learning 29% faster today
  • 150,000+ documents available
  • Just £6.99 a month

Not the one? Search for your essay title...
  • Join over 1.2 million students every month
  • Accelerate your learning by 29%
  • Unlimited access from just £6.99 per month

See related essaysSee related essays

Related GCSE Organic Chemistry essays

  1. Marked by a teacher

    Viscosity of Alkanes

    3 star(s)

    Alkane Time in seconds Average Time Average Speed (cm/s)* Test 1 Test 2 Test 3 Test 4 Test 5 Pentane 2.3 1.68 0.81 3.04 2.01 1.968 3.81 Hexane 1.98 1.39 3.18 2.92 3.28 2.54 2.95 Octane 6.6 2.28 3.22 1.38 3.45 4.766 1.57 Decane 2.98 15.42 7.92 14.75 8.64 9.942

  2. Marked by a teacher

    Investigating the rate of reaction between magnesium and hydrochloric acid

    3 star(s)

    However the rate increases if there is more particles of acid and less water in the solution, as the magnesium will be able to find the acid faster and there will be more chances of successful collisions. Evaluation I have identified my anomalous result that are highlighted in table no.5

  1. Peer reviewed

    Should food additives be banned

    3 star(s)

    This allows you to avoid foods containing specific additives if you wish. Giving an additive an E number means that it has passed safety tests and has been approved for use here and in the rest of the EU. I got this information from http://www.food.gov.uk/safereating/chemsafe/additivesbranch/ I think it is a

  2. Pollution from the internal combustion engine.

    head - these oil layers can absorb and desorb hydrocarbon components of the fuel before and after combustion respectively, so a fraction of the fuel can escape the initial combustion process unburned.

  1. Do fuel cell systems offer a feasible alternative to combustion engines in minimizing the ...

    Of the various technological developments that might offer a cleaner alternative to internal combustion engines I intend to consider the pros and cons of fuel cell systems in road vehicles. In places where they could in future be widely marketed, they are expected to not only meet emission standards (like the EU's)

  2. In this report the effects of fire and explosion are examined based on quantitative ...

    This is fundamental to the dynamics of fire and explosion. A flammable gas or vapour will only burn in air if the composition lies between certain limits. These limits are called the "Upper" and "Lower" flammability limits. If an excess of fuel vapour is present in the fuel-air mixture, then

  1. GCSE Chemistry Revision Notes - everything!

    ? Br2+ (g) + 2e- Loss of electrons is oxidation. Bromide ions are oxidised to bromine molecules. Reduction happens at the cathode and oxidation happens at the anode. Positive ions are cations because they are attracted to the cathode. The negative ions move to the anode, where they give electrons to the electrodes.

  2. Notes on crude oil and its by-products.

    than can be used directly and fewer short-chain hydrocarbons than required With increasing chain length, the hydrocarbons become less flammable, more viscous and therefore less useful. So there isn?t much use for these heavy fractions, but there?s more of it, whilst there?s a higher demand for short-chain hydrocarbons.

  • Over 160,000 pieces
    of student written work
  • Annotated by
    experienced teachers
  • Ideas and feedback to
    improve your own work