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Crude oil is a complex mixture of substances - Edexcel - GCSE Chemistry - Question 6 - 2018 - Paper 1
Question 6
Crude oil is a complex mixture of substances. (a) Crude oil can be separated into useful fractions by fractional distillation. Figure 7 shows a fractional distilla... show full transcript
Worked Solution & Example Answer:Crude oil is a complex mixture of substances - Edexcel - GCSE Chemistry - Question 6 - 2018 - Paper 1
Step 1
Which of the following is a trend in a property of the fractions obtained from the top to those obtained from the bottom?
Answer
The boiling points of the fractions increase as we move from the top of the column to the bottom. This trend can be attributed to the larger molecular size and stronger intermolecular forces in the heavier fractions, which require more energy (higher temperature) to overcome.
Step 2
Step 3
Explain why alkanes are described as hydrocarbons.
Answer
Alkanes are described as hydrocarbons because they are composed exclusively of carbon (C) and hydrogen (H) atoms. Their molecular structure consists of carbon chains with hydrogen atoms attached, which is characteristic of hydrocarbons.
Step 4
Explain the pattern shown by this graph.
Answer
The graph indicates that as the number of carbon atoms in the alkane increases, the boiling points also increase. This trend is because larger alkane molecules have greater surface area, leading to stronger van der Waals forces between the molecules. Consequently, more energy is required to break these intermolecular attractions, resulting in higher boiling points.
Step 5
Step 6
On the axes provided, draw the reaction profile of this reaction.
Answer
The reaction profile of an endothermic reaction should begin at the energy level of the reactants, rising to a peak representing the activation energy, and then descending to a lower energy level for the products, indicating that the energy of the products is lower than that of the reactants.
Step 7