Fractional distillation separates crude oil into useful fractions such as petrol and kerosene. Petrol contains alkanes typically ranging from C5H12\text{C}_5\text{H}_{12}C5H12 to C10H22\text{C}_{10}\text{H}_{22}C10H22, while kerosene contains heavier alkanes typically ranging from C12H26\text{C}_{12}\text{H}_{26}C12H26 to C16H34\text{C}_{16}\text{H}_{34}C16H34.
Which statement correctly explains the difference in physical properties between the alkanes found in kerosene and those in petrol?
Alkanes in kerosene have a larger surface area of contact, leading to stronger temporary dipole-induced dipole forces, a higher viscosity, and lower volatility than those in petrol.
Alkanes in petrol have a larger surface area of contact, resulting in stronger London dispersion forces, higher boiling points, and lower volatility than those in kerosene.
Alkanes in kerosene have more covalent bonds within each molecule, requiring more thermal energy to break these bonds during boiling, which increases their boiling point relative to petrol.
Alkanes in petrol have a lower hydrogen-to-carbon ratio, allowing them to burn completely with a cleaner, less smoky flame than those in kerosene.
130 exam-style questions on Edexcel GCSE Chemistry 9.1 Fuels, covering 9.1.1 Hydrocarbons and crude oil, 9.1.2 Fractional distillation of crude oil and its fractions, 9.1.3 The alkanes as a homologous series, 9.1.4 Complete and incomplete combustion, 9.1.5 Pollutants from burning fuels, 9.1.6 Hydrogen as a fuel and non-renewable fossil fuels, and 9.1.7 Cracking of larger alkanes. Each one has a worked solution and a mark scheme showing where the marks go.