Pearson Edexcel International GCSE (9–1) · CHEMISTRY · Unit
Organic Chemistry
785 practice questions
Topics covered
Practice questions
31–40 of 133 · Hard
Question 31
8 marks · Hard
Answer and see the solution →Organic chemists use systematic naming to identify complex molecules. The rules for the type of compound and for branched chains must both be followed for names to be correct.
(a)[3 marks]State the name given to the type of compound with the structure shown below. Explain which features of the structure identify this type.
Displayed formula for a compound. (b)A branch is added to the compound in part (a) by replacing one of the hydrogen atoms on the second carbon (counting from the left) with an ethyl group (–CH2CH3).
i) Draw the full displayed formula for the new compound.
ii) Using the rules for branched chains and the type of compound, write the full systematic (IUPAC) name for your structure.
(i)[2 marks]Draw the displayed formula for the molecule described.
(ii)[3 marks]Give the IUPAC name for the compound you have drawn, following the rules for branched chains.
Question 32
2 marks · Hard
Answer and see the solution →Explain how burning fuels derived from crude oil can contribute to acid rain. Include the names of the main gases involved.
Question 33
5 marks · Hard
Answer and see the solution →Crude oil formed over millions of years from the remains of organisms.
(a)[2 marks]Describe what happened to the dead sea plants and animals that led to the formation of crude oil.
(b)[2 marks]State two conditions necessary for crude oil to form from these remains.
(c)[1 mark]Explain why crude oil is considered a non-renewable resource.
Question 34
2 marks · Hard
Answer and see the solution →State what crude oil is composed of. Name the two elements found in all hydrocarbons in crude oil.
Question 35
2 marks · Hard
Answer and see the solution →State two changes in the physical properties of hydrocarbon fractions as the number of carbon atoms in their molecules increases.
Question 36
5 marks · Hard
Answer and see the solution →Crude oil is separated into fractions by fractional distillation. Two fractions, A and B, are collected at different heights in the fractionating column.
(a)[2 marks]Fraction A consists of large hydrocarbon molecules, while fraction B consists of small hydrocarbon molecules. State which fraction is collected higher up the column. Give a reason for your answer.
(b)[2 marks]Describe how the physical properties (boiling point and viscosity) of fraction A compare to those of fraction B.
(c)[1 mark]Suggest one use for fraction B, based on its physical properties.
Question 37
2 marks · Hard
Answer and see the solution →Explain why hydrocarbons with larger molecules are less useful as fuels than those with smaller molecules.
Question 38
2 marks · Hard
Answer and see the solution →State the trend in boiling point and position within the fractionating column for hydrocarbons with increasing chain length, giving a reason for each.
Question 39
5 marks · Hard
Answer and see the solution →Pentane (C₅H₁₂) is a hydrocarbon fuel.
(a)[2 marks]Write a balanced chemical equation, using formulae, for the complete combustion of pentane.
(b)The supply of oxygen is reduced so that incomplete combustion occurs.
(i)[2 marks]Name two products, other than water, that could be formed during incomplete combustion of pentane.
(ii)[1 mark]Explain why less heat is released during incomplete combustion than during complete combustion.
Question 40
2 marks · Hard
Answer and see the solution →State two reasons why the fractions obtained from crude oil by fractional distillation are useful as fuels.