Crude oil is a complex mixture of hydrocarbons that can be separated into fractions. The table below shows the range of boiling points for four fractions obtained during the fractional distillation of a crude oil sample:
| Fraction | Range of boiling point in ∘C^{\circ}\text{C}∘C |
|---|---|
| P | 30–80 |
| Q | 80–120 |
| R | 120–180 |
| S | 180–240 |
(i) Identify the fraction that is the most viscous at room temperature.
(ii) Identify the fraction that contains compounds with the smallest molecules.
Fraction S contains undecane, which is a straight-chain alkane with eleven carbon atoms.
(i) Determine the molecular formula of undecane.
(ii) Give the general formula of the homologous series that includes undecane.
(i) Octadecane, C18H38\text{C}_{18}\text{H}_{38}C18H38, is a long-chain alkane. It can undergo cracking to yield dodecane, C12H26\text{C}_{12}\text{H}_{26}C12H26, and two molecules of the same alkene. Write a balanced chemical equation for this cracking reaction.
(ii) State two conditions used in industry for catalytic cracking.