AQA GCSE Chemistry (8462), Higher tier · Organic chemistry › Carbon compounds as fuels and feedstock
Practise Properties of hydrocarbons. 12 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
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Name the two products of the complete combustion of a hydrocarbon.
Carbon dioxide and water
What is meant by the viscosity of a liquid?
How easily it flows (how thick it is).
Write a balanced symbol equation for the complete combustion of hexane.
2C6H14 + 19O2 → 12CO2 + 14H2O
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy2 marks
(a) Which statement about alkanes is correct? Tick (✓) one box.[1]
As the chain length increases, the boiling point increases
As the chain length increases, the flammability increases
As the chain length increases, the viscosity decreases
Short-chain alkanes are more viscous than long-chain alkanes
(b) What is meant by the viscosity of a liquid?[1]
Show the answer and mark scheme
(a)Answer: As the chain length increases, the boiling point increases
(b)Answer: How easily it flows (how thick it is).
how easily the liquid flows / its resistance to flowing / how thick it is
Question 2Medium5 marks
Alkanes are used as fuels.
(a) Balance the equation for the complete combustion of propane. C3H8 + .....O2 → .....CO2 + .....H2O[1]
(b) Write a balanced equation for the complete combustion of butane, C4H10.[2]
(c) During combustion, the carbon and hydrogen in the fuel are oxidised. What does 'oxidised' mean here?[1]
(d) Explain why the combustion of hydrocarbons is useful.[1]
Show the answer and mark scheme
(a)Answer: C3H8 + 5O2 → 3CO2 + 4H2O
C3H8 + 5O2 → 3CO2 + 4H2O
(b)Answer: 2C4H10 + 13O2 → 8CO2 + 10H2O
correct formulae: C4H10 + O2 → CO2 + H2O
balanced: 2C4H10 + 13O2 → 8CO2 + 10H2O
(c)Answer: They gain oxygen.
they gain oxygen / combine with oxygen
(d)Answer: It releases a lot of energy, so hydrocarbons can be used as fuels.
it releases (a lot of) energy / is exothermic, so hydrocarbons are useful fuels
Question 3Hard7 marks
(a) Explain why the boiling points of the alkanes increase as the number of carbon atoms increases.[3]
(b) Short-chain hydrocarbons are in high demand as fuels. Give two reasons why short-chain hydrocarbons are better fuels than long-chain hydrocarbons.[2]
(c) Write a balanced equation for the complete combustion of dodecane, C12H26.[2]
Show the answer and mark scheme
(a)Answer: The molecules get larger, so the intermolecular forces are stronger and more energy is needed to overcome them.
the molecules are larger
so the intermolecular forces (forces between the molecules) are stronger
so more energy is needed to overcome these forces
(b)Answer: They are more flammable (easier to ignite) and less viscous (flow and evaporate more easily).
they are more flammable / ignite more easily
they are less viscous / flow or evaporate more easily