The correct order of octane number of butane, pentane, hexane and cyclohexane is
butane > cyclohexane > pentane > hexane
The correct answer is: Option 1 – butane > cyclohexane > pentane > hexane
Let’s examine the relative octane numbers of the four hydrocarbons:
| Compound | Structure Type | Approximate Octane Number | Explanation |
|---|---|---|---|
| Butane (C₄H₁₀) | Branched alkane (n-butane and isobutane) | ~92–94 | High due to small size and branching potential |
| Cyclohexane (C₆H₁₂) | Cyclic alkane | ~83 | Higher than straight chains due to ring strain reducing premature combustion |
| Pentane (C₅H₁₂) | Straight-chain alkane | ~62 | Linear structure; more prone to knocking |
| Hexane (C₆H₁₄) | Straight-chain alkane | ~48 | Longer straight chain = lower resistance to knocking |
Butane > Cyclohexane > Pentane > Hexane
| Option | Why It's Incorrect |
|---|---|
| 2 (butane > pentane > cyclohexane > hexane) | Places cyclohexane below pentane, which is incorrect; cyclohexane has a higher octane number. |
| 3 (butane > pentane > hexane > cyclohexane) | Places cyclohexane at the bottom, which is factually incorrect. |
| 4 (cyclohexane > butane > pentane > hexane) | While cyclohexane is high, butane has a higher octane number, especially its branched isomer. |
Based on molecular structure and experimental values, the correct order of octane numbers is:
Butane > Cyclohexane > Pentane > Hexane
Hence, the correct answer is: Option 1.
The handle of pressure cookers is made of plastic because it should be made non-conductor of heat. The plastic used here is the first man-made plastic, which is:
The PCl 5 molecule has trigonal bipyramidal structure. Therefore, the hybridization of p orbitals should be __________.
Methanol is toxic because
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Which one of the following is not an allotrope of carbon?
Match List-I with List-II and select the correct answer using the code given below the Lists:
List-I (Compound/Molecule) | List-II (Shape of Molecule) |
A. CH 3F | 1. Trigonal planar |
B. HCHO | 2. Tetrahedral |
C. HCN | 3. Trigonal pyramidal |
D. NH 3 | 4. Linear |
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In which of the following, functional group isomerism in not possible?
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1. Concentrated \(H_2SO_4\) is used as a dehydrating agent in esterification reaction.
2. The hydrophilic part of soap is oil and it dissolves in water.
3. Nickel is used as a catalyst in converting vegetable oil into fat.
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