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:
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 |
The x/monomers used for the synthesis of Nylon 6 is/are _________.
Consider the following chemical reaction: aFe 2O 3(s) + bCO(g) → cFe (s) + dCO 2
In the balanced chemical equation of the above, which of the following will be the values of the coefficients a, b, c and d respectively?Which one of the following polymers does not contain glucose units?
The PCl 5 molecule has trigonal bipyramidal structure. Therefore, the hybridization of p orbitals should be __________.
Methanol is toxic because
Which one of the following is known as cetane?
Which one of the following is not an allotrope of carbon?
The catalyst used in the manufacture of methyl alcohol from water gas is
A carbon compound when heated in excess of concentrated sulphuric acid at 443K gives ethene. The compound is an________.
The manmade fiber obtained by chemical treatment of wood pulp is _____.
Plastic is not related to which of the following
The Peroxyacetyl Nitrate (PAN) is: