Crude oil is a useful resource which is recovered from sedimentary rock by drilling - Leaving Cert Chemistry - Question 6 - 2021
Question 6
Crude oil is a useful resource which is recovered from sedimentary rock by drilling. Crude oil is a mixture of hydrocarbons and is separated into a number of differe... show full transcript
Worked Solution & Example Answer:Crude oil is a useful resource which is recovered from sedimentary rock by drilling - Leaving Cert Chemistry - Question 6 - 2021
Step 1
Explain the underlined term.
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Answer
Hydrocarbons are organic compounds consisting entirely of hydrogen and carbon atoms. They are the primary constituents of crude oil and can be categorized into alkanes, alkenes, and alkynes based on their bonding structure.
Step 2
List the three fractions named above in order of increasing boiling point.
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Answer
The three fractions in order of increasing boiling point are:
Light gasoline
Kerosene
Gas oil (diesel oil)
Step 3
As they separate in a fractionating column, where (high up or low down) would you expect to collect the hydrocarbons
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(i) with the fewest carbon atoms,
The hydrocarbons with the fewest carbon atoms would be collected high up in the fractionating column, where the temperature is lower and lighter fractions condense.
(ii) with the highest boiling points?
Those with the highest boiling points would be collected low down in the column, as heavier fractions condense in the higher temperatures nearer to the heat source.
Step 4
Which of the three fractions named above
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Answer
(i) is used as a fuel for jet aircraft,
Kerosene is the fraction commonly used as a fuel for jet aircraft due to its suitable properties for combustion.
(ii) is often catalytically cracked to make smaller molecules for use in petrol?
Light gasoline is often catalytically cracked to produce smaller hydrocarbons that are beneficial for petrol.
Step 5
What term is used as a measure of the tendency of a fuel to cause knocking in an engine?
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Answer
The term used to measure the tendency of a fuel to cause knocking in an engine is 'octane rating'.
Step 6
(i) Why were lead compounds previously added to petrol?
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Answer
Lead compounds were added to petrol to increase the octane rating of the fuel, which improved engine performance by reducing knocking.
Step 7
(ii) Why was the addition of lead compounds to petrol discontinued?
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The addition of lead compounds to petrol was discontinued due to health and environmental concerns, as lead is a toxic substance that poses serious health risks to humans and can contaminate the environment.
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