Crude oil is a complex mixture of substances - Edexcel - GCSE Chemistry - Question 6 - 2018 - Paper 1

The general formula of an alkane is D C_nH_{2n+2}. Alkanes are saturated hydrocarbons, meaning they contain only single bonds between carbon atoms.

Alkanes are described as hydrocarbons because they are organic compounds that consist solely of hydrogen and carbon atoms. This means that they have carbon atoms bonded to hydrogen atoms, which is the defining characteristic of hydrocarbons.

The graph shows that as the number of carbon atoms in the alkane molecule increases, the boiling point also increases. This trend can be attributed to the fact that larger molecules have more electrons, leading to stronger van der Waals forces between them, which require more energy (higher temperature) to break.

The fraction that is most likely to need to be cracked is fuel oil, as it is produced in higher amounts compared to its demand.

The reaction profile graph should show the energy of the reactants at a higher level than the energy of the products, indicating an endothermic reaction. The activation energy should be labeled as the peak of the curve.

The cracking of dodecane can be represented as: $C_{12}H_{26} \rightarrow C_{n}H_{2n+2} + other \ products$ where the specific products depend on the reaction conditions.