Question

Which mixture is given by Dodecane in the presence of Platinum?

Answer 1

Hint: The heat-induced fragmentation of a chemical in the absence of air is known as pyrolysis. It's not the same as setting fire to something. It occurs when there is no air available, preventing the oxidation of chemicals. The pyrolysis of alkanes is known as cracking. Noble metals like Platinum,palladium are used as a catalyst in the pyrolysis process.

Complete answer:
When alkane vapours pass across red-hot metal in the absence of air, they decompose into smaller, simpler hydrocarbons. Without the use of a catalyst, this process takes place at high pressures and temperatures. A catalyst, such as palladium or platinum, is required for this reaction at low pressures and temperatures. During the fractionation process, considerable amounts of hydrocarbons are usually obtained.
The hydrocarbon molecules randomly break down into smaller hydrocarbon compounds during cracking, with a few of the products containing carbon-carbon double bonds.
The following are the factors that contribute to the creation of products during cracking:
Temperature and pressure
Nature of alkane
Presence or absence of a catalyst
Alkane cracking is governed by a mechanism known as the free radical mechanism. It is very important in the petroleum sector. By cracking, the higher molecules of an alkane are converted into lower molecules (from petrol ${C_6}$ to ${C_{11}}$ ).
When dodecane (a component of kerosene oil) is heated at $973K$ under the catalytic action of palladium, nickel, or platinum, it produces a combination of pentane and heptane as pyrolysis products.
\[{{\text{C}}_{12}}{{\text{H}}_{26}}\xrightarrow{{{\text{Pt / Pd / Ni}}}}{{\text{C}}_7}{{\text{H}}_{16}} + {{\text{C}}_5}{{\text{H}}_{10}} + {\text{Other Products}}\]

Note:
Pyrolysis is the process of a chemical decomposing with the use of heat. Cracking is the pyrolysis of higher alkanes to generate a combination of lower alkanes and alkenes. It's usually done by heating the higher alkanes to high temperatures at pressures ranging from \[6 - 7{\text{ atm}}\], either with or without a catalyst. Pyrolysis of alkanes occurs through a free radical mechanism, which involves the breaking of \[{\text{C}} - {\text{H}}\] and \[{\text{C}} - {\text{C}}\] bonds.