Petrodiesel vs Biodiesel topic test PDF

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Summary

Unit 3 Chemistry VCE practice question based upon biodiesel VS petrodiesel.
Hopefully this will help you all get a head start for chemistry!...

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QUESTION 1 With reference to the molecular structure of both petrodiesel and biodiesel state why incomplete combustion is less of a problem for biodiesel than it is for petrodiesel. Solution

QUESTION 2 With reference to intermolecular bonding explain why a sample of biodiesel is more likely to be found as a solid at low temperatures than a sample of petrodiesel. Solution

QUESTION 3 With reference to intermolecular bonding explain why biodiesel is more viscous than petrodiesel. Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 4 Why is energy content of diesel is measured in kJ/g as opposed to kJ/mol? Solution

QUESTION 5 Are saturated hydrocarbons likely to be found in petrodiesel or biodiesel? Give a reason for your answer. Solution

QUESTION 6 The table below lists some of the properties of biodiesel and petrodiesel.

Describe and explain the difference in viscosity, under the same conditions, of the two fuels and how this would affect the flow of each fuel through fuel lines in an engine. Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 7 Consider the following molecules. A B C D E

CH3(CH2)6CH3 , CH3(CH2)6COOH , CH3CHCH(CH2)3CH3 CH3(CH2)6COOCH3 CH3OH

(a)

Which molecule is likely to be found in a sample of biodiesel? Give a reason for your answer.

(b)

Which molecule is likely to be found in a sample of petrodiesel? Give a reason for your answer.

(c)

Which molecule is likely to form one of the reactants in the formation of biodiesel?

(d)

Write a chemical equation for the formation of biodiesel using the reactant in (c) above.

Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 8 Which of the following is not an advantage of using biofuels instead of petroleum?* A B C D

Biofuels are renewable Biofuels work well at low temperatures Biofuels are produced domestically Biofuels can be made from different materials

QUESTION 9 What are the products of burning both petrodiesel and biodiesel? A B C D

Carbon dioxide and water Hydrogen gas and water Carbon dioxide and oxygen Carbon monoxide and hydrogen

QUESTION 10 Which fuel, biodiesel or petrodiesel produces less carbon dioxide per gram of fuel? Solution

QUESTION 11 Why does the combustion of petrol (and other fossil fuels) add to the amount of carbon dioxide in the atmosphere whilst burning of biofuels such as biodiesel and bioethanol does not add to the amount of carbon dioxide in the atmosphere over the long term? Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 12 What are the differences between petroleum and biodiesel in terms of chemical structure? Solution

QUESTION 13 Complete the following table by inserting a tick (✓) in the appropriate column. Property

Biodiesel

Petrodiesel

Biodegradable Renewable Higher flash point Lower cloud point Higher energy efficiency Higher sulfur dioxide emissions Higher viscosity Dipole-dipole intermolecular bonding 1

Higher energy content ( kJg  )

QUESTION 14 Explain the difference and why it exists of the cloud point of petrodiesel and biodiesel. Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 15 (a)

Calculate the number of litres of biodiesel that are required to be burnt to produce the same amount of energy as 2.5 kg of petrodiesel. Assume that combustion occurs in an unlimited supply of oxygen.

(b)

Calculate the mass of carbon dioxide that would be produced from 3.91 kg of biodiesel. Density (biodiesel) = 0.89 kg L–1 Energy biodiesel = 38 MJkg-1 Energy petrodiesel = 43 MJkg-1 Mass (carbon dioxide)/kg biodiesel = 2.52 kg

Solution

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 16 (a)

What is renewable energy?

(b)

Give two examples of renewable energy.

(c)

Provide two differences between fossil fuels and renewable energy.

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QUESTION 1 The oxygen in the biodiesel molecules result in a more efficient burn. The net result is that less CO is produced because there is more oxygen to produce CO2. This does not occur in petrodiesel, which is a hydrocarbon. QUESTION 2 The cloud point is dependent on polarity. The more polar a molecule is, the easier it is for it to form a repeating crystal structure and become solid. Biodiesel, because it contains oxygen, is more polar than standard diesel and therefore more prone to developing small crystals. Biodiesel forms dipole-dipole bonding between molecules. QUESTION 3 The higher viscosity of biodiesel is due to the presence of stronger interparticle forces, namely dipole-dipole interactions, as the molecule is polar. This pulls biodiesel chains closer to each other, making the liquid thicker or more viscous. Furthermore, as biodiesel molecules are usually longer than petrodiesel molecules, there are greater numbers of dispersion forces between the biodiesel hydrocarbon chains, drawing them even closer to each other. Longer chains also result in greater entanglement, which increases the viscosity as well. QUESTION 4 Diesel is a mixture of molecules for different lengths and therefore, it is not possible to determine a molar mass or calculate the amount in mole reacting. QUESTION 5 Saturated molecules are more likely to be found in petrodiesel, which is primarily composed of alkanes. Many triglycerides contain at least one carbon to carbon double bond and therefore, the fatty acid esters produced are likely to be unsaturated. QUESTION 6 Biodiesel has higher viscosity and therefore flows less easily through fuel lines. This is due to stronger intermolecular attraction between biodiesel molecules than petrochemical molecules due to • •

Stronger dispersion forces because of the longer carbon chains. Dipole-dipole attractions due to the presence of the polar ester functional group.

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QUESTION 7 (a)

Molecule D as it has an ester functional group, which is a feature of biodiesel molecules.

(b)

Molecule A as petrodiesel is mainly composed of alkanes.

(c)

Molecule E

(d)

QUESTION 8

Answer is B

QUESTION 9

Answer is A

QUESTION 10 Biodiesel. QUESTION 11 When combusting petrol, which is a fossil fuel, carbon is released that has been out of the carbon cycle for millions of years. The carbon in biofuels has been taken in from the atmosphere that is part of the carbon cycle. When burnt, the biofuel releases carbon dioxide to the atmosphere, replacing the gas that was taken up by the plants used to produce it. i.e. the net amount of carbon dioxide in the atmosphere does not change. QUESTION 12 Petroleum mainly consists of saturated hydrocarbons (alkanes) as it is made up from carbon and hydrogen atoms and single carbon to carbon bonds. Biodiesel molecules are primarily made from carbon, hydrogen and oxygen and include the ester functional group which has a carbon atom bonded to two oxygen atoms, one through a single covalent bond and the other via a double covalent bond. These molecules are known as esters.

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 13 Property

Biodiesel

Biodegradable

✓

Renewable

✓

Higher flash point

✓

Petrodiesel

Lower cloud point

✓

Higher energy efficiency

✓

Higher sulfur dioxide emissions

✓

Higher viscosity

✓

Dipole-dipole intermolecular bonding

✓

1

Higher energy content ( kJg  )

✓

QUESTION 14 The cloud point refers to the temperature at which small crystals begin to form. Biodiesel has the higher cloud point – i.e. crystals form at a higher temperature. The main thing that determines the cloud point is polarity. The more polar a molecule is, the easier it is for it to form a repeating crystal structure and become solid. Biodiesel, because it contains oxygen, is more polar than standard diesel and therefore more prone to developing small crystals. QUESTION 15

(a) Step 1: Calculate the energy in the 2.5 kg of petrodiesel. 1 2 Energy in 2.5 kg of petrodiesel  2.5 kg  43 MJkg  1.08 10 MJ

Step 2: Calculate the mass of biodiesel that would release the same amount of energy.

m (biodiesel ) 

Energy released 1.08 102   2.842 kg 38 Energy per kg

Step 3: Calculate the corresponding volume.

d

m V

V  (b)

m 2.842   3.193  3.2 L d 0.89

m( CO2 )  3.91  2.52  9.85 kg

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Unit 3 & 4 Chemistry – Topic Test

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QUESTION 16 (a)

Renewable energy is derived from natural resources, which are quickly and easily replenished by nature.

(b)

Solar energy using solar cells, hydroelectricity from flowing waters, ethanol from corn, electricity from wind using turbines, geothermal heat, and bio-fuels from biomass such as grass and wood chips are all examples of renewable energy.

(c)

Difference 1: Fossil fuels such as oil and coal are extracted from under the earth’s surface and transported. The process causes spills and leakages. Solid, liquid and air-born wastes pollute the earth’s surface and natural resources. They harm several habitats. Damages to water, land and air over time has created diseases and deaths. On the other hand, renewable energy is produced from biomass such as wood chips, grass, and from natural energy sources such as sunlight, wind and water. Hence, it does not produce pollution. Difference 2: Mining of coal causes destruction of land and pollution of the surrounding habitats. Diseases such as cancer in the lungs and digestive system are caused by pollution of air, land and water from coal dust, gases and slurry. Miners have to dig deeper and deeper for coal because it not replenish. Renewable energy does not pollute land or water resources and it is not destructive. We can repeatedly use it without running out of it. Moreover, it does not have hidden costs related to health. Difference 3: Emission of sulfur dioxide is responsible for acid rain. Renewable energy sources produce no or very little sulfur dioxide as compared to fossil fuels. Difference 4: Hydraulic fracking or pressure fracturing is a process for extraction of natural gas. Each fracking requires 80 to 300 tons of highly toxic and hazardous chemicals that are poured up to a depth of 8000 feet. Once the natural gas is extracted, these wells are repeatedly fractured to remove natural gas and they can then go further deeper and continue fracturing. Hence, natural gas and chemicals leaks into water wells.

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Unit 3 & 4 Chemistry – Topic Test

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