4c-Alkanes Flashcards
Q: What is crude oil?
A: Crude oil is a finite (non-renewable) fossil fuel formed from the remains of ancient marine organisms. It is a mixture of hydrocarbons, mainly alkanes.
Q: How is crude oil formed?
A: Crude oil is formed over millions of years from the buried remains of plankton and marine organisms, subjected to high pressure and temperature under sedimentary rock layers.
Q: What is fractional distillation?
A: Fractional distillation is the process of separating crude oil into different fractions based on their boiling points.
How does fractional distillation work?
Crude oil is heated until it evaporates.
The vapors enter a fractionating column.
The column has a temperature gradient (hot at the bottom, cool at the top).
Hydrocarbons condense at different levels based on their boiling points.
Fractions with low boiling points (small molecules) condense at the top.
Fractions with high boiling points (large molecules) condense at the bottom.
Refinery gases boiling poit and use
< 40°C
Bottled gas, fuel for heating
Gasoline (Petrol) boiling point and use
40-100°C
Fuel for cars
Kerosene boiling point and use
150-250°C
Jet fuel
Diesel boiling point and use
250-350°C
Fuel for trucks, trains
Fuel oil boiling point and use
> 350°C
Ship fuel, power stations
Bitumen boiling point and use
Residue
Road surfaces, roofin
What trends occur as hydrocarbon molecules increase in size?
Boiling point increases (larger molecules need more energy to vaporize).
Viscosity increases (larger molecules are thicker and flow less easily).
Flammability decreases (larger molecules burn less easily).
Volatility decreases (larger molecules evaporate less easily).
fraction in curde oil order
1-Refinery gases
2-Gasoline (Petrol)
3-Kerosene
4-Diesel
5-Fuel oil
6-Bitumen
What is cracking?
A: Cracking is the process of breaking down long-chain hydrocarbons into shorter, more useful molecules. It produces alkanes and alkenes.
Why is cracking necessary?
A: Cracking helps meet the high demand for short-chain fuels (e.g., petrol) and produces alkenes used in making plastics.
What are the conditions for cracking?
A:
Catalytic Cracking: 500°C, zeolite catalyst.
Steam Cracking: High temperature (>800°C), steam.
What is an example of a cracking reaction?
A: Decane → Octane + Ethene
C₁₀H₂₂ → C₈H₁₈ + C₂H₄
Practical: Investigating Cracking
Catalytic Cracking of Paraffin:
Method:
Heat liquid paraffin over an alumina catalyst.
Collect the gas produced and test with bromine water.
Practical: Investigating Cracking
Catalytic Cracking of Paraffin:
Positive result
Positive Result: Bromine water turns colorless, indicating the presence of an alkene.
Practical: Investigating Cracking
Catalytic Cracking of Paraffin:
Negative reuslt
Negative Result: No color change if only alkanes are present.
