Some chemical reactions of organic compounds
4 marks · NormalThe following two reactions involve organic compounds:
CH4(g) + Cl2(g) → CH3Cl(g) + HCl(g). State the type of reaction and explain why it is classified as this type.
C3H8(g) + 5O2(g) → 3CO2(g) + 4H2O(l). State the type of reaction and explain your answer.
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(a) Substitution; because a hydrogen atom in methane is replaced by a chlorine atom.
(b) Combustion; because propane reacts with oxygen to form carbon dioxide and water, releasing energy.
Common mistakes: Calling combustion a substitution or addition; Forgetting to explain that in substitution a group/atom is replaced; Not stating oxygen is involved in combustion
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Marking points
B1 (a) · 1 mark · States reaction is substitution.
B2 (a) · 1 mark · Explains that a hydrogen atom is replaced by a different atom (chlorine).
B3 (b) · 1 mark · States reaction is combustion.
B4 (b) · 1 mark · Explains that the compound combines with oxygen to produce carbon dioxide and water (or references burning).
Worked solution
(a) This is a substitution reaction. A hydrogen atom in methane is replaced by a chlorine atom to give chloromethane and hydrogen chloride.
(b) This is a combustion reaction. Propane reacts with oxygen, producing carbon dioxide and water, which is typical of combustion reactions involving organic compounds.