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Crude oil is a mixture of hydrocarbons - Edexcel - GCSE Chemistry - Question 9 - 2023 - Paper 2
Question 9
Crude oil is a mixture of hydrocarbons. Crude oil can be separated into useful fractions by the process of fractional distillation in a fractionating column. Figure... show full transcript
Worked Solution & Example Answer:Crude oil is a mixture of hydrocarbons - Edexcel - GCSE Chemistry - Question 9 - 2023 - Paper 2
Step 1
Which row shows the correct uses for bitumen, diesel oil and fuel oil?
Answer
The correct answer is C: surfacing roads, fuel for trains, fuel for large ships. This implies that bitumen is primarily used for road surfacing, diesel oil is suitable for fueling trains, while fuel oil is utilized for large ships.
Step 2
Explain the trend in the viscosity of the fractions.
Answer
Viscosity increases down the column as molecules are larger (containing more carbon atoms). This is due to stronger intermolecular forces acting between the larger hydrocarbon molecules, which require more energy to overcome. As such, larger molecules exhibit greater resistance to flow, resulting in higher viscosity.
Step 3
Deduce the molecular formula of hydrocarbon X.
Answer
To find the molecular formula of X, we first calculate the molar mass of Y. Given that the relative formula mass of Y is 56 and its empirical formula is C₂H₄, we can determine the molecular formula.
The molecular formula is a multiple of the empirical formula. The empirical formula mass for C₂H₄ is:
Now, we check how many times the empirical formula fits into the relative formula mass of Y: rac{56}{28} = 2
Therefore, the molecular formula of Y is C₄H₈. Since hydrocarbon X produces one molecule of hexane (C₆H₁₄) and one molecule of olefin (Y), the molecular formula of hydrocarbon X is: .