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Petroleum serves as a source of large number of chemicals. These chemicals obtained from petroleum are known as petrochemicals. Thousands of organic compounds are made from the refined products of petroleum. These compounds are further used in the manufacture of thousands of products which satisfy our basic needs and also provide luxury consumer items. Uses of petrochemicals are listed in Fig. 51.3.


Fig. 51.3. Petrochemicals and their uses

Thus, source of ethanol, ethane-1, 2-diol and ethanoic acid is ethene which in turn is obtained from petroleum.

Similarly, methanol, freon-12, chloroform, CCl4 and obtained from methane

 Group Discussion

Name three petrochemicals and state their sources and one use of each of them.

Some chemicals derived from methane and ethene are given below in the form of flow sheet: 



  1. I.                   Objective Type Question

Select the most appropriate choice from the options given as and (d) after each question:

1. Which of the following commands is the highest price in oil industry?

(a) Light sweet crude oil

(b) Heavy sweet crude oil

(c) Light sour crude oil

(d) Heavy sweet crude oil

2. Light oil has API gravity

(a) less than 31.1o

(b) less than 22.3o

(c) between 22.3o and 31.1o
(d) higher than 31.1o


3. Separation of crude oil into various fractions is possible because the fractions have different .

(a) melting points

(b) densities

(c) boiling points

(d) viscosity


  1. Which one of the following is not a petrochemical?

(a) methanol

(b) ethanol

(c) benzene

(d) glass.


  1. Which of the following fractions of petroleum has the highest boiling range?

(a) Kerosene

(b) Fuel oil
(c) Gasoline

(d) Petroleum ether


II. Fill in the Blanks

  1. Complete the following sentences by supplying appropriate words:

(i)                 The percentage of sulphur in sweet crude oil is …

(ii)                The full form of API gravity is …

(iii)             API gravity of heavy oil is …

(iv)              Quality of gasoline is expressed ill terms of   …

(v)                IUPAC name of iso-octane is …

(vi)              Octane number of heptane is …


III. Discussion Questions

  1. What is petroleum? How was it formed? What is its composition?
  2. Discuss the classification of crude oil by

(i)                 sulphur content

(ii)               API gravity

  1. Explain the classification of crude oil as light and heavy.

Explain why light and sweet crude oils are preferred to heavy and sour crude oils.

  1. How is petroleum mined? What are the two main elements present in petroleum?
  2. Discuss the classification of crude oil on the basis of geographic location of its source. Explain why there are differences in price for the same quantity of crude oil from
    different sources.
  3. Describe the process of fractional distillation of petroleum with the help of a labelled diagram of distillation tower. Name any four products obtained. State the temperature at which each one of them is obtained.
  4. The boiling points of three components P, Q and R of petroleum are 170°C, 250°C and 350°C respectively. If the mixture of these three is fractionally distilled, in which order
    would you get these substances?
  5. Draw a labelled diagram of fractional distillation tower used to obtain petrol. Name the products obtained at each of the following temperatures:

(a) 170°C

(b) 250°C

(c) 360°C

(d) 450°C


  1. Out of gasoline and kerosene oil which is more volatile?
  2. Point out one difference for the following pair of fuels: petrol and kerosene oil.
    1. What is petroleum gas and how is it obtained? What are the uses of petroleum gas? What is the main constituent of petroleum gas?
    2. Give chemical composition of liquified petroleum gas. Name the compound that is added to LPG to detect its leakage.
    3. How is domestic cooking gas obtained? Why is it called LPG?
    4. Write short notes on:

(i)              cracking

(ii)            reforming

(iii)          octane number

(iv)           anti-knock agents.

  1. What is the relation between structures of constituent hydrocarbons of gasoline on its octane number?

22. What are petrochemicals? Name three petrochemicals and state their sources.



I. Objective Type Question

1. (a) 2. (d) 3. (c)
4. (d) 5. (b)  

II. Fill in the Blanks


(i) less than 0.5%

(ii) American Petroleum Institute Gravity
(iii) below 22.3°

(iv) 2, 2, 4-trimethylpentane
(v) 0 (zero)