Fuels Flashcards
List the types of fossil fuels and their state in standard conditions.
- Solid - Coal
- Liquid - Crude oil (petroleum)
- Gas - Natural gas (methane)
List the products of petroleum fractional distillation, from lowest boiling point to highest boiling point.
- Petroleum gas
- Petrol
- Naphtha
- Kerosene
- Diesel oil
- Lubricating oil
- Bitumen
How many carbon atoms per molecule does PETROLEUM GAS have and what is it used for?
1-4 Carbon atoms
Used as fuel for cooking
How many carbon atoms per molecule does PETROL have and what is it used for?
5-10 Carbon atoms
Used as fuel for motorcars
How many carbon atoms per molecule does NAPHTHA have and what is it used for?
8-12 Carbon atoms
Used as raw material to make other chemicals (eg alcohols, plastic, drugs)
How many carbon atoms per molecule does KEROSENE have and what is it used for?
10-14 Carbon atoms
Fuel for jet aircrafts
Fuel for cooking and heating
How many carbon atoms per molecule does DIESEL OIL have and what is it used for?
15-25 Carbon atoms
Fuel for diesel engines of buses, lorries and taxis
How many carbon atoms per molecule does LUBRICATING OIL have and what is it used for?
19-35 Carbon atoms
Used as machine lubricant, wax, polishes
How many carbon atoms per molecule does BITUMEN have and what is it used for?
More than 70 Carbon atoms
Used to surface roads
How does fractional distillation separate petroleum into different fractions?
- Petroleum is heated and evaporated. The hot vapour rises up and comes into contact with the cooler surfaces up the column, condensing into a liquid.
- When more hot vapour reaches the condensed liquid, the liquid gains heat and evaporates again. Hence, evaporation and condensation occur repeatedly up the column.
- Since the temperature of the column decreases with an increase in height, the fractions with lower boiling points will condense at higher parts of the column, while those with higher boiling points will condense at lower parts of the column.
Explain why an increase in the molecular mass of the hydrocarbons lead to an increase in boiling point?
- As molecular mass increases, the molecules’ size increases, so the total surface area in contact between the molecules increases.
- Hence, there is stronger Van der Waals’ forces of attraction between the molecules and more energy is needed to overcome this.
- The boiling point is therefore higher.
What are the 2 renewable fuel alternatives?
Biofuel (biogas, biodiesel, bioethanol)
Hydrogen
How is biogas formed?
Methane gas formed from methane fermentation where organic wastes from plants and animals are decomposed by methane germs.
How is biodiesel formed?
Used vegetable oil and fats are treated and reacted with methanol in the presence of a catalyst, in a transesterification process. The products are separated into biodiesel and glycerin.
How is bioethanol formed and how is it good?
From the fermentation of crops like corn and sugarcane. Ethanol is mixed with petrol to power motor vehicles.
It is a form of carbon neutral fuel as the carbon dioxide released from ethanol combustion will be reabsorbed by plants for photosynthesis.
What are the 3 advantages of using hydrogen as fuel?
- Renewable
- Produces a lot more energy than other fuels.
- Only product formed is water, which does not pollute the environment.
What are the 2 disadvantages of using hydrogen as fuel?
- Hydrogen has low density so a larger storage volume is required compared to other fuels.
- Hydrogen is highly flammable so it requires special precaution for storage and transport.
Explain the processes in a hydrogen fuel cell.
- Hydrogen and oxygen are pumped into the fuel cell at the anode and cathode respectively.
- Hydrogen gas reacts with hydroxide ions to produce water.
H2 + 2OH- –> 2H2O + 2e- - Oxygen gas reacts with water to produce hydroxide ions.
O2 + 2H2O + 4e- –> 4OH- - Electrons flow from the anode to the cathode, generating energy in the form of electricity.
Overall equation:
2H2 + O2 –> 2H2O
What is the electrolyte used in the cell?
Aqueous potassium hydroxide.
