Crude oil, fuels and pollutantsEdexcel International A Level Chemistry: Mind map

Exam questions on Crude oil, fuels and pollutants

1. A refinery heats crude oil, a mixture of hydrocarbons, and feeds the vapour into a fractionating column that is hottest at the bottom and coolest at the top. Fractions are drawn off at different heights: refinery gas, petrol (about C₅ to C₁₀), kerosene (about C₁₀ to C₁₆) and diesel (about C₁₄ to C₂₀), with a residue left at the bottom.
   Write an equation for the cracking of dodecane, C₁₂H₂₆, to give ethene and one other hydrocarbon, and state one reason why refineries crack heavy fractions.2 marks
2. A garage runs a petrol car engine in a closed workshop to test it. The petrol contains traces of sulfur compounds, and the engine becomes hot enough for nitrogen from the air to react. The exhaust gas contains carbon monoxide, oxides of nitrogen, sulfur dioxide, carbon particulates and unburned hydrocarbons.
   Explain why running the engine in a closed workshop is dangerous because of carbon monoxide.2 marks
3. A technician studies the combustion of octane, C₈H₁₈, in a petrol engine. Take the molar volume of a gas at room temperature and pressure to be 24.0 dm³ mol⁻¹. Relative atomic masses: H = 1.0, C = 12.0.
   Write balanced equations for (i) the complete combustion of octane, (ii) incomplete combustion of octane to carbon monoxide and water only, (iii) incomplete combustion of octane to carbon particulates (carbon) and water only.3 marks