CIE iGCSE Co-Ordinated Science C11.5 Alkenes Exam Style Questions Paper 1
▶️ Answer/Explanation
In organic chemistry, the ending of a compound’s name indicates the type of compound:
- -ane ending indicates an alkane (a saturated hydrocarbon with only single carbon-carbon bonds).
- -ene ending indicates an alkene (an unsaturated hydrocarbon containing at least one carbon-carbon double bond).
- -ol ending indicates an alcohol (contains an -OH group).
Looking at each structure:
- A: \( \text{CH}_4 \) (methane) — only single bonds, so -ane.
- B: \( \text{C}_2\text{H}_5\text{OH} \) (ethanol) — contains an -OH group, so -ol.
- C: \( \text{C}_2\text{H}_6 \) (ethane) — only single bonds, so -ane.
- D: \( \text{C}_2\text{H}_4 \) (ethene) — contains a carbon-carbon double bond (C=C), so -ene.
Therefore, the structure that represents a compound with a name ending in ‘ene’ is Structure D.
✅ Answer: (D)
▶️ Answer/Explanation
Alkenes are unsaturated hydrocarbons containing a carbon-carbon double bond (\(\mathrm{C=C}\)).
The structure with a double bond between two carbon atoms is the alkene. The other structures showing single bonds are alkanes.
✅ Answer: (C)
The structure with a double bond between two carbon atoms is the alkene. The other structures showing single bonds are alkanes.
✅ Answer: (C)
▶️ Answer/Explanation
Ethene, \(\text{C}_2\text{H}_4\), contains a reactive carbon–carbon double bond.
This double bond allows ethene to undergo addition reactions.
When steam is added across the double bond in the presence of an acid catalyst, water is incorporated into the molecule.
This addition of steam converts ethene directly into ethanol, \(\text{C}_2\text{H}_5\text{OH}\).
✅ Answer: (D)
This double bond allows ethene to undergo addition reactions.
When steam is added across the double bond in the presence of an acid catalyst, water is incorporated into the molecule.
This addition of steam converts ethene directly into ethanol, \(\text{C}_2\text{H}_5\text{OH}\).
✅ Answer: (D)
▶️ Answer/Explanation
Aqueous bromine (bromine water) is decolourised by alkenes through electrophilic addition across the \(\text{C=C}\) double bond — the molecule in option B contains a C=C double bond (it is an alkene).
Alkanes (saturated molecules with only C–C single bonds) do not react with bromine water under normal conditions, so the other options showing only single bonds would not decolourise it.
✅ Answer: (B)
Alkanes (saturated molecules with only C–C single bonds) do not react with bromine water under normal conditions, so the other options showing only single bonds would not decolourise it.
✅ Answer: (B)
▶️ Answer/Explanation
Ethene molecules contain a C=C double bond, which opens up so monomers can join together directly.
Many ethene monomers joining to form a long chain (polyethene) with no other product is addition polymerisation.
Cracking, fermentation and thermal decomposition are unrelated processes that do not describe this joining reaction.
✅ Answer: (A)
Many ethene monomers joining to form a long chain (polyethene) with no other product is addition polymerisation.
Cracking, fermentation and thermal decomposition are unrelated processes that do not describe this joining reaction.
✅ Answer: (A)