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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 fractioanlizing column. Figu... show full transcript
Worked Solution & Example Answer:Crude oil is a mixture of hydrocarbons - Edexcel - GCSE Chemistry - Question 9 - 2023 - Paper 2
Step 1
Step 2
Explain the trend in the viscosity of the fractions.
Answer
Viscosity increases down the column because the molecules are larger (or longer) due to having more carbon atoms. As the carbon chain length increases, stronger intermolecular bonds or forces of attraction develop between the molecules, leading to increased viscosity.
Step 3
Deduce the molecular formula of hydrocarbon X.
Answer
- The relative formula mass of Y is 56.
- The empirical formula of Y is C2H4, which means it has a molecular formula of C2H4 with a molar mass of 28 g/mol.
- Since X produces one molecule of C6H14 (which has a molecular mass of 86 g/mol), the total for X must be 86 g/mol + 28 g/mol = 114 g/mol.
- Since the empirical formula of Y is C2H4, we know that to find molecular formula X, we establish:
- Let the molecular formula of X be C₄H₈ + C6H14 + C2H4
- X = C₈H₁₈.
- Thus, the molecular formula of hydrocarbon X is C8H18.