MC test: Fossil fuels

Multiple choice test on C.2 Fossil fuels

Use the following 'quiz' to test your knowledge and understanding of this sub-topic. As this relates to a sub-topic on the options you may need access to the IB data booklet.

If you get an answer wrong, read through the explanation carefully to learn from your mistakes.

What does the octane number of gasoline (petrol) refer to?

The octane number refers to a mixture that has the same resistance to auto-ignition as a mixture of 2,2,4-trimethylpentane and heptane with the same octane number. It does not means that the gasoline itself necessarily is made up of that mixture.

 

Which lists the compounds in order of increasing octane number?

The shorter the carbon chain in straight-chain alkanes the higher the octane number and the more branched the chain the higher the octane number. The actual values are: octane (−20), heptane (0) and 2,2,4-trimethylpentane (100).

 

Which are uses for the fraction of crude oil that boils between 40 oC and 160 oC?

I. gasoline (petrol)

II. diesel

III. chemical feedstock

Diesel has a higher boiling range (between about 160oC and 380 oC)

 

Which are reforming reactions?

I.

II.

III.

I is cracking as a larger molecule is being broken down into two smaller molecules. II is isomerization and III is aromatization. Both isomerization and aromatization are reforming reactions as the organic products contain the same number of carbon atoms as the starting material.

 

Which explain why sulfur is removed from crude oil during the refinery process?

I. To reduce sulfur dioxide emissions when the products undergo combustion as fuels.

II. To remove the possibility of sulfur poisoning the catalysts used in the refining processes.

III. To prevent hydrogen sulfide being formed during the refining processes.

Removal of sulfur prevents both the formation of acid rain caused by the release of sulfur dioxide when sulfur-containing fuels are burned and the possibility of poisoning the transition metals used as catalysts in refining processes. The sulfur is normally removed by converting it into hydrogen sulfide in a process known as hydrodesulfurization.

 

Which mixture will have an octane rating greater than 100?

2,2,4-trimethylpentane has an octane rating of 100 and methylbenzene (an aromatic hydrocarbon) has an even higher rating (114) so together they will give an octane rating greater than 100.

 

What is the main component of syngas (SNG)?

Syngas (SNG) is synthetic natural gas and is mainly methane.

 

What is the main reason for coal liquefaction?

Approximately 30% of the energy content of coal is lost during the conversion process to liquid fuels and the combustion of liquid fuels still produces carbon dioxide which contributes to global warming.

 

Sulfur hexafluoride has a global warming potential of twenty three thousand times that of carbon dioxide over 100 years.  How does it contribute significantly to a carbon footprint even though it contains no carbon?

Carbon footprints take into account the global warming effect of all greenhouse gases and expresses them as CO2 equivalents. SF6 is a very powerful greenhouse gas and is long-lived but as it is only present in the atmosphere in low concentrations it contributes about 0.2% of the overall greenhouse effect.

 

Which statements are true about cracking reactions?

I. The saturated products have a higher octane number than the reactants.

II. The unsaturated products can be used to make plastics

III. They involves the breaking of C−C bonds.

Cracking involves the breaking of C−C bonds to make smaller more useful molecules from larger hydrocarbon molecules.

 

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