Explain briefly the process of cracking or pyrolysis. from Chem

Previous Year Papers

Download Solved Question Papers Free for Offline Practice and view Solutions Online.

Test Series

Take Zigya Full and Sectional Test Series. Time it out for real assessment and get your results instantly.

Test Yourself

Practice and master your preparation for a specific topic or chapter. Check you scores at the end of the test.
Advertisement

 Multiple Choice QuestionsLong Answer Type

111.

Discuss:
(a) Nitration of an alkane.
(b) Sulphonation of alkane.

1654 Views

 Multiple Choice QuestionsShort Answer Type

112. What do you mean by isomerization of alkanes?
209 Views

 Multiple Choice QuestionsLong Answer Type

Advertisement

113.

Explain briefly the process of cracking or pyrolysis.


Cracking: Alkanes, when subjected to high temperature (670-970 K.) in the presence of a catalyst, are decomposed into smaller molecules. This process of breaking down the less volatile higher hydrocarbons into different types of more volatile lower hydrocarbons by the application of heat is called cracking or pyrolysis. The cracking of alkanes involves the cleavage of C-C and C-H bonds. For example,

Pyrolysis of alkanes is supposed to occur by the free radical mechanism. Preparation of oil gas or petrol gas from kerosene oil or petrol involves the principle of pyrolysis. For example, heating to 973K in the presence of Pt, Pd or Ni gives a mixture of heptane and pentene.

 

Cracking is of two types:
(i) Thermal cracking: It may be carried out in the vapour phase or in the liquid phase. It is difficult to control and gives rise to complex product mixtures. 
(ii) Catalytic cracking. It is carried out at a temperature of 670- 820 K using silica and alumina as a catalyst. 
Catalytic cracking is useful as it gives gasoline having higher octane number.
The products formed during cracking depends upon:
(i) the structure of starting alkane
(ii) the pressure applied
(iii) use of a catalyst.

519 Views

Advertisement
114. What are the products of chlorination of methane? Describe the mechanism of the formation of each?
129 Views

Advertisement
115.

What is reforming (or aromatization)? Why is it done?

293 Views

 Multiple Choice QuestionsShort Answer Type

116.

Define the terms conformation and conformational isomerism.

119 Views

117.

Define the terms conformation and conformational isomerism.

103 Views

118. Discuss the conformation in the molecule of ethane.
409 Views

Advertisement

 Multiple Choice QuestionsLong Answer Type

119.

Out of staggered and eclipsed conformations of ethane, which is more stable and why ?

202 Views

 Multiple Choice QuestionsShort Answer Type

120.

Can eclipsed and staggered conformations of ethane be isolated? Give reasons.

195 Views

Advertisement