CIE iGCSE Co-Ordinated Science C11.4 Alkanes Exam Style Questions Paper 2
▶️ Answer/Explanation
A correctly balanced equation must use molecular oxygen, \( O_2 \), not free oxygen atoms, which rules out options C and D.
Balancing carbon gives 5 carbon atoms split between \( CO_2 \) and \( CO \), and balancing hydrogen gives \( 6H_2O \); checking option A: \( 3CO_2 + 2CO + 6H_2O \) uses \( (3\times2)+2+6 = 14 \) oxygen atoms, matching \( 7O_2 \).
Option B does not balance oxygen atoms correctly, so it is incorrect.
✅ Answer: (A)
Balancing carbon gives 5 carbon atoms split between \( CO_2 \) and \( CO \), and balancing hydrogen gives \( 6H_2O \); checking option A: \( 3CO_2 + 2CO + 6H_2O \) uses \( (3\times2)+2+6 = 14 \) oxygen atoms, matching \( 7O_2 \).
Option B does not balance oxygen atoms correctly, so it is incorrect.
✅ Answer: (A)
▶️ Answer/Explanation
Longer alkane chains have stronger intermolecular (van der Waals) forces due to a greater number of electrons and surface area of contact between molecules.
Stronger intermolecular forces mean more energy is needed for molecules to escape into the gas phase, so evaporation is slower.
This means mass lost through evaporation decreases steadily as the number of carbon atoms in the chain increases, giving a downward-sloping line.
✅ Answer: (A)
Stronger intermolecular forces mean more energy is needed for molecules to escape into the gas phase, so evaporation is slower.
This means mass lost through evaporation decreases steadily as the number of carbon atoms in the chain increases, giving a downward-sloping line.
✅ Answer: (A)
Question
Reactants for three chemical processes are listed.
1 ethene + steam
2 ethene + hydrogen
3 ethene forming poly(ethene)
Which processes form saturated hydrocarbons?
(A) 1, 2 and 3
(B) 1 and 2 only
(C) 1 and 3 only
(D) 2 and 3 only
▶️Answer/Explanation
Ans : D
Question
The Haber process is used to make ammonia.
Which statement about the Haber process is not correct?
A A vanadium(V) oxide catalyst is used.
B The nitrogen used is obtained from the air.
C The pressure used is 200 atmospheres.
D The temperature used is 450 ºC.
▶️Answer/Explanation
Ans : A
Question
The cracking of decane molecules is represented by the equation shown.
What is Y?
- A: C₄H₈
- B: C₄H₁₀
- C: C₇H₁₄
- D: C₇H₁₆
▶️Answer/Explanation
Answer: B
Explanation: The cracking of decane (C₁₀H₂₂) produces smaller alkanes and alkenes. In this case, Y is C₄H₁₀, which is butane.