FuelsEdexcel GCSE Chemistry: Flashcards
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What is a hydrocarbon?
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- What is a hydrocarbon?
- A compound that contains carbon and hydrogen only.
- What is crude oil?
- A complex mixture of hydrocarbons (mainly alkanes), an important finite resource for fuels and petrochemical feedstock.
- How does fractional distillation separate crude oil?
- Crude oil is heated and vaporised; vapours rise up a column that is cooler towards the top, so hydrocarbons condense out at different heights according to their boiling points.
- Name the fraction used as fuel for aircraft.
- Kerosene.
- Name the fraction used for surfacing roads and roofs.
- Bitumen.
- How do properties change from the top to the bottom of the fractionating column?
- Chain length, boiling point and viscosity increase, and the fractions become harder to ignite.
- What is a homologous series?
- A family of compounds with the same general formula, differing by CH2 between members, showing a gradual change in physical properties and similar chemical properties.
- What are the products of complete combustion of a hydrocarbon?
- Carbon dioxide and water, with energy released.
- What can incomplete combustion of a hydrocarbon produce?
- Carbon monoxide and/or carbon (soot), as well as carbon dioxide and water.
- Why is carbon monoxide dangerous?
- It is a toxic gas that binds to haemoglobin in the blood, stopping it carrying oxygen around the body.
- What causes acid rain from burning fuels?
- Sulfur impurities in fuel burn to form sulfur dioxide, which dissolves in rainwater.
- Why do burning fuels in engines produce oxides of nitrogen?
- At the high temperatures inside an engine, oxygen and nitrogen from the air react together.
- What is cracking and why is it necessary?
- Cracking breaks down large saturated alkanes into smaller, more useful molecules (some unsaturated alkenes); it is necessary because there is more demand for short-chain fractions than fractional distillation alone provides.
- Give one advantage and one disadvantage of hydrogen as a car fuel compared with petrol.
- Advantage: only produces water when burned (no CO2/CO/soot). Disadvantage: difficult and costly to store/transport safely, with limited refuelling infrastructure.