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Different car engines are designed to use different fuels - Edexcel - GCSE Chemistry - Question 4 - 2012 - Paper 1
Question 4
Different car engines are designed to use different fuels. These fuels include diesel, ethanol, hydrogen, LPG (liquefied petroleum gas) and petrol. (a) LPG contains... show full transcript
Worked Solution & Example Answer:Different car engines are designed to use different fuels - Edexcel - GCSE Chemistry - Question 4 - 2012 - Paper 1
Step 1
Complete the structure of a molecule of propane, C₃H₈, showing all bonds.
Answer
The molecular structure of propane, C₃H₈, includes three carbon (C) atoms connected in a chain, each bonded to hydrogen (H) atoms to fulfill the tetravalence of carbon. The structure can be represented as follows:
H H H
| | |
H - C - C - C - H
| | |
H H H
This indicates that there are single bonds between each carbon atom and between the carbon and hydrogen atoms.
Step 2
Describe how you would use limewater to show that carbon dioxide is produced.
Answer
To demonstrate that carbon dioxide is produced when propane burns, I would bubble the gas through limewater (a saturated solution of calcium hydroxide). As carbon dioxide is introduced into the limewater, it reacts with calcium hydroxide to form calcium carbonate, which causes the solution to turn milky. This change indicates the presence of carbon dioxide, as shown in the following reaction:
The milky appearance of the limewater confirms the production of carbon dioxide.
Step 3
Explain a problem caused by the products of this incomplete combustion.
Answer
Incomplete combustion of propane leads to the formation of harmful byproducts, particularly carbon monoxide (CO) or soot. Carbon monoxide is a colorless, odorless gas that is toxic and can be lethal to humans as it binds with hemoglobin in the blood, reducing the blood's ability to carry oxygen. This creates a risk of suffocation or poisoning. Additionally, soot can accumulate, leading to air pollution and respiratory problems, affecting both health and the environment.
Step 4
Which of the following can be produced as a biofuel? Put a cross (X) in the box next to your answer.
Answer
D ethanol
Ethanol is a biofuel produced through the fermentation of sugars. It is considered a renewable source because it can be derived from plant materials, unlike fossil fuels which are finite.
Step 5
Explain how a biofuel is different from a fossil fuel.
Answer
Biofuels are derived from biological materials (like plants or organic waste) and are considered renewable resources. They can be replenished over time as compared to fossil fuels, which are formed from decomposed organic matter over millions of years and are non-renewable. Furthermore, biofuels generally result in a lower net carbon footprint because they can contribute to a closed carbon cycle.
Step 6
Explain which fuel, A or B, would be best for powering a car.
Answer
Fuel A, which is in a gaseous state, has a higher energy output of 142 MJ per kg compared to fuel B, which produces only 47 MJ per kg. Although fuel A has a limited availability, its higher energy yield makes it a more efficient choice for powering a car. Thus, fuel A would be better suited for vehicle operation based on energy production.