The diagram shows a butane (C₄H₁₀) gas lighter being used to ignite methane (CH₄) gas in a Bunsen burner - Leaving Cert Chemistry - Question 6 - 2017
Question 6
The diagram shows a butane (C₄H₁₀) gas lighter being used to ignite methane (CH₄) gas in a Bunsen burner.
(a) Why are both of these fuels classed as hydrocarbons? ... show full transcript
Worked Solution & Example Answer:The diagram shows a butane (C₄H₁₀) gas lighter being used to ignite methane (CH₄) gas in a Bunsen burner - Leaving Cert Chemistry - Question 6 - 2017
Step 1
Why are both of these fuels classed as hydrocarbons?
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Answer
Both butane and methane are classified as hydrocarbons because they consist entirely of hydrogen and carbon atoms. This characteristic is fundamental to their classification, as hydrocarbons are defined as organic compounds that only contain carbon (C) and hydrogen (H).
Step 2
Give one natural source of methane.
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Answer
A natural source of methane is marshy areas such as paddy fields, where decomposition of organic waste occurs. Additionally, methane is produced in the digestive systems of ruminant animals.
Step 3
Why are mercaptans added to methane gas before it is piped to consumers?
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Mercaptans are added to methane gas to provide an odor to the otherwise odorless gas. This is important for safety reasons, as it allows for the detection of gas leaks, thereby preventing potential hazards.
Step 4
To which homologous series do both methane and butane belong?
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Answer
Both methane and butane belong to the homologous series known as alkanes.
Step 5
Name one other member of this series and draw the structure of one of its molecules.
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One other member of the alkane series is ethane (C₂H₆). The structure of ethane can be represented as:
H H
| |
H-C-C-H
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H H
Step 6
Name the oil refining process used to separate the hydrocarbons in crude oil.
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Answer
The oil refining process used to separate the hydrocarbons in crude oil is called fractional distillation.
Step 7
What is meant by the octane number of a fuel?
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Answer
The octane number of a fuel is a measure of its tendency to resist pre-ignition, also known as auto-ignition, during combustion. A higher octane number indicates better resistance to knocking.
Step 8
Name one method by which the octane number of a hydrocarbon fuel can be improved.
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One method to improve the octane number of a hydrocarbon fuel is through isomerization. This process involves converting straight-chain hydrocarbons into branched-chain hydrocarbons, which have higher octane ratings. Other methods include the addition of oxygenates, such as methanol, or the use of catalytic cracking.
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