5.1 Cracking Hydrocarbons
Large Hydrocarbon molecules can be broken down into smaller molecules by a process called cracking.
· Heating a mixture of hydrocarbon vapours and steam to very high temperatures.
· Passing hydrocarbon vapours over hot catalyst
During cracking thermal decomposition reaction produce a mixture of smaller molecules.
· Alkanes – saturated hydrocarbons with general formula CnH2n+2. (Useful fuels)
· Alkenes – unsaturated hydrocarbons, contain fewer hydrogen atoms with same number of carbon atoms, with general formula CnH2n. Have double bonds making them more reactive.
C10H22 à 800 C + catalyst à C5H12 + C3H6 + C2H4
Decane -------------------à Pentane +Propene + Ethene