Petroleum is a complex mixture of hydrocarbons - VCE - SSCE Chemistry - Question 7 - 2006 - Paper 1

Alkanes with shorter carbon chains have weaker intermolecular forces, specifically London dispersion forces. These forces are primarily influenced by the size and surface area of the molecules. Shorter-chain alkanes have fewer electrons and a smaller surface area, leading to weaker dispersion forces compared to longer-chain alkanes, which have more electrons and a larger surface area, resulting in stronger forces that require more energy (higher temperatures) to overcome for boiling.

Fractional distillation involves heating petroleum in a distillation column. The mixture is separated based on the boiling points of the components. The column is designed to achieve a temperature gradient; lighter fractions with lower boiling points rise to the top, while heavier fractions with higher boiling points descend to the bottom. Separate fractions are collected at different heights in the column as they condense, effectively separating the different hydrocarbons. This process is vital for refining petroleum into usable products such as gasoline, kerosene, and diesel.

When propane (C3H8) is cracked, four likely products can be:

1. Ethene (C2H4)
2. Propene (C3H6)
3. Butane (C4H10)
4. Butene (C4H8)

1. Hydrogenation of Ethene:

   C2H4 + H2 → C2H6

   In this reaction, ethene reacts with hydrogen to form ethane.

2. Combustion of Ethene:

   C2H4 + 3O2 → 2CO2 + 2H2O

   In this reaction, ethene combusts in the presence of oxygen to yield carbon dioxide and water.