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Crude oil is found in the Earth’s crust - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Question 3
Crude oil is found in the Earth’s crust. (a) Which of the statements about crude oil is correct? A crude oil is a finite resource B crude oil is a mixture of the e... show full transcript
Worked Solution & Example Answer:Crude oil is found in the Earth’s crust - Edexcel - GCSE Chemistry Combined Science - Question 3 - 2018 - Paper 1
Step 1
Which of the statements about crude oil is correct?
Answer
The only correct statement about crude oil is A: 'crude oil is a finite resource.' This indicates that crude oil is limited and cannot be replenished within a human time scale. The other statements are incorrect because:
- B is not accurate as crude oil is a mixture of various compounds, not just hydrogen and carbon.
- C is incorrect since not all molecules in crude oil contain carbon rings; many are linear chains.
- D is misleading because while crude oil is used as a fuel, the statement lacks the nuance regarding its proper use in various forms.
Step 2
These substances
Answer
The correct answer is C: 'are in the same homologous series.' Ethane, octane, and pentadecane are all alkanes, demonstrating similarities in their chemical structure and properties, specifically differing by -CH₂ groups. The other options are incorrect as:
- A is incorrect because they have different molecular formulas.
- B is wrong since they have different boiling points owing to the increasing chain length of the alkanes.
- D is also incorrect because they produce similar products when combusted.
Step 3
Use a word from the box to complete each of the sentences about the fractional distillation of crude oil.
Answer
For the first blank, the correct word is 'heated': Before crude oil is passed into the column it is heated.
For the second blank, the appropriate word is 'condensed': The vapour has been condensed.