why cracking of decane makes a large number of alkanes?

Answer 1

Decane (C10H22) has ten carbons in an linked straight chain.

When this molecule is 'cracked' the chain can break at any point in a random manner, eg. between carbon one and carbon two or say between carbon five and carbon six. This produces another shorter ALKANE and an ALKENE.

These two shorter chains must contain the total number of carbons and hydrogens that are contained in the original molcule. Atoms can be neither added nor taken away.

(Long) Alkane -> cracking -> (Shorter)Alkane + Alkene
Decane (C10H22) - > C5H12 + C5H10
pentane + pentene

Decane - > C6H14 + C4H8
hexane + butene
and so on......

Answer 2

Decane is a Carbon Chain with 10 carbon atoms. When you "crack" it, (usually by heating) the chain breaks up into smaller constituents. So you could form other alkanes from one decane.

Answer 3

Because decane has 10 carbon atoms so when it breaks down by thermal cracking for example, it can give numerous alkanes with less carbon like hexanes(6 carbons), pentanes(5), butanes(4), propanes(3) and so on...

Answer 4

Cracking of large hydrocarbon molecules results in a number of smaller compounds.
Decane can be made to break up into combinations of two or more compounds whose total Carbon atoms add up to 10.
In order to produce a mixture of Alkanes, Hydrogenation is also necessary.
Cracking processes include Catalytic cracking and Hydro-cracking.
Catalytic cracking is used to convert heavy hydrocarbon fractions obtained by vacuum distillation into a mixture of more useful products such as gasoline and light fuel oil.
In this process, the input stream goes through a chemical breakdown, under controlled heat (450 – 500°C), and pressure, in the presence of a Catalyst.
The cracking reaction yields components for gasoline, LPG, Olefins, Gas oils… etc.
These products are then passed through a fractionator to be separated and further processed.

Hydro-cracking can increase the yield of gasoline components, as well as being used to produce light distillates. It produces no residues, only light compounds. Hydro-cracking is catalytic cracking in the presence of hydrogen. The extra hydrogen saturates, or hydrogenates, the chemical bonds of the cracked hydrocarbons and creates isomers with the desired characteristics. Hydro-cracking is also a treating process, because the hydrogen combines with contaminants such as sulphur and nitrogen, allowing them to be removed.

An older process once used extensively is 'Thermal-cracking' where the cracking of the long chain molecules was carried out at very high temperature.