Topic 9D: Crude oil, combustion and alkanes Flashcards
What is crude oil?
Crude oil is a mixture of hydrocarbons
What is a hydrocarbon?
A hydrocarbon is a molecule that is made up of hydrogen and carbon only.
What are the properties of longer chains of hydrocarbons?
- Less flammable
- Less volatile
- More viscous
- Higher boiling point
Define fractional distillation.
Fractional distillation is a process of separating a liquid mixture into its constituent parts.
Explain the process of the fractional distillation of crude oil.
- Crude oil heated until it turns into vapour
- Tower has temperature gradient (hot at bottom, cool at top)
- Vapour rises until reaches boiling point
- Vapour condenses to liquid and collected off as fractions
- Larger molecules = higher BPT
smaller molecules = lower BPT
Why do longer chains of hydrocarbons have higher boiling points?
They have more intermolecular forces, so more energy is needed to overcome the IMFs.
Name the fractions in the fractionating column of the crude oil. BOTTOM TO TOP
State the uses of each fraction.
- Bitumen (tarmac in roads)
- Diesel (power up larger vehicles)
- Kerosene (jet fuel)
- Naphtha (petrochemicals)
- Petrol (fuel in cars)
- Refinery gases (domestic heating and cooking)
As the boiling temps of the fractions increase, what is the trend in colour?
As temperature increases, the colour gets darker.
As the boiling temps of the fractions increase, what is the trend in viscosity?
As temp increases, the viscosity increases
As you go down the fraction, what happens to the boiling points?
They increase as you go down
What is released when a fuel is burnt?
Heat energy is released.
methane + oxygen (complete combustion) forms what products
carbon dioxide and water
methane + oxygen (incomplete combustion) forms what
carbon + carbon monoxide + water
Why is carbon monoxide poisonous?
It combines with the haemoglobin in red blood cells and replace the oxygen with carbon monoxide
Why are nitrogen oxides able to form in car engines?
The engines will reach very high temperatures, allowing the inert nitrogen to react with oxygen to form nitrogen oxides
