Which one of the following statements related to octane number is NOT correct?
Show Hint
Straight-chain alkanes → lower octane number.
Branched alkanes and aromatics → higher octane number.
Octane number is a direct measure of resistance to engine knocking.
- Linear alkanes with higher carbon number have higher octane number.
- Branching in linear alkanes increases their octane number.
- Catalytic reforming of hydrocarbons increases their octane number.
- Gasoline quality is measured in terms of octane number.
The Correct Option is A
Solution and Explanation
Step 1: Octane number measures the fuel’s ability to resist knocking. Iso-octane (2,2,4-trimethylpentane) is defined with an octane number of 100.
Step 2: Straight-chain alkanes (n-alkanes) generally have low octane numbers because they ignite easily, leading to knocking. Increasing the carbon chain length in linear alkanes actually decreases their octane number.
Step 3: Branching in alkanes (Option B) increases the octane number since it enhances resistance to knocking.
Step 4: Catalytic reforming (Option C) increases octane number by converting straight-chain hydrocarbons into branched or aromatic compounds.
Step 5: Gasoline quality is indeed measured using the octane number (Option D).
Final Answer: The incorrect statement is: \[ \boxed{\text{(A)}} \]
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