The number of saturated and unsaturated bonds in cyclohexane are:
- A.9 and 0 respectively.
- B.18 and 3 respectively.
- C.18 and 0 respectively.
- D.9 and 3 respectively.
Correct answer
Explanation
The correct answer is C, 18 and 0 respectively. Cyclohexane, C6H12, has 6 C–C single bonds and 12 C–H single bonds, 18 single bonds in all and no double or triple bond.
Cyclohexane is a saturated cyclic hydrocarbon, a cycloalkane. Its six carbon atoms form a ring joined by single bonds, and each carbon also carries two hydrogen atoms. Counting gives 6 bonds in the ring plus 6 × 2 = 12 bonds to hydrogen, so 18 bonds, all of them single (saturated) bonds. It fits the general formula CnH2n of cycloalkanes. Benzene, C6H6, is the six-carbon ring that has three double bonds.
A is wrong: it counts only half of the bonds.
B is wrong: three double bonds belong to benzene, not cyclohexane.
D is wrong: it halves the single bonds and wrongly adds double bonds.
Exam tip: cyclohexane C₆H₁₂ = 18 single bonds; benzene C₆H₆ = 12 sigma bonds and 3 pi bonds.
Practice Questions
View allConsider the following animals :
1. Hedgehog
2. Marmot
3. Pangolin
To reduce the chance of being captured by predators, which of the above organisms rolls up/roll up and protects/protect its/their vulnerable parts?
- A.1 and 2
- B.2 only
- C.3 only
- D.1 and 3
Show answer
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- A.Congress grass
- B.Elephant grass
- C.Lemongrass
- D.Nut grass
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Lemongrass and its close relative citronella grass yield aromatic oils that keep mosquitoes away, so they are the base of many natural repellents.
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- A.Conducting copper coil
- B.Electric heating coil
- C.Semi conductor diode
- D.Rheostat
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A diode does not obey Ohm's law: the current through it is not proportional to the voltage across it. An ohmic conductor gives a straight-line graph of current against voltage, so its resistance stays constant at a fixed temperature.
Read the full explanation →What is the formula mass of anhydrous sodium carbonate? (Given that the atomic masses of sodium, carbon and oxygen are 23 u, 12 u and 16 u respectively)
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- B.106 u
- C.83 u
- D.53 u
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- A.Bauxite
- B.Quartz
- C.Feldspar
- D.Pitchblende
Show answer
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