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Crude oil is a complex mixture of substances - Edexcel - GCSE Chemistry Combined Science - Question 4 - 2018 - Paper 1
Question 4
Crude oil is a complex mixture of substances. (a) Crude oil can be separated into useful fractions by fractional distillation. Figure 3 shows a fractional distillat... show full transcript
Worked Solution & Example Answer:Crude oil is a complex mixture of substances - Edexcel - GCSE Chemistry Combined Science - Question 4 - 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 correct trend is B: the ease of ignition increases. As we move down the fractions in the distillation column, the simpler hydrocarbons (like gases and petrol) with lower boiling points naturally ignite more easily compared to heavier fractions.
Step 2
Step 3
Explain why alkanes are described as hydrocarbons.
Answer
Alkanes are described as hydrocarbons because they are organic compounds composed entirely of hydrogen and carbon atoms. Their structure consists of carbon chains or rings bonded to sufficient hydrogen atoms to fulfill carbon's tetravalent nature.
Step 4
Explain the pattern shown by this graph.
Answer
The graph illustrates that as the number of carbon atoms in alkanes increases, the boiling point also increases. This is primarily due to stronger van der Waals forces between molecules as the molecular size increases, leading to higher energy required to break these intermolecular attractions.
Step 5
Step 6
Draw the reaction profile of this reaction.
Answer
The diagram should illustrate an endothermic reaction, showing the energy level increasing as reactants transform into products. The reactants' energy should be labeled as higher than that of the products, and an activation energy peak should be clearly indicated.
Step 7