6 past paper MCQs on Molecular Orbital Treatment of Benzene, from the Chemistry of Hydrocarbons unit of MDCAT Chemistry. The year each question appeared is shown where known; tap “Show answer” for the correct option and a short solution.
1.The three alternate double bonds in benzene are called: (MDCAT 2022)
Correct answer: (a) delocalized bonds
The six $p$ electrons spread over all six carbons, so the bonds are delocalized rather than three fixed double bonds.
2.The ratio of sigma to pi electrons in benzene is: (MDCAT 2022)
Correct answer: (c) 4 : 1
Benzene has twelve sigma bonds, so 24 sigma electrons, against 6 pi electrons.
3.Ratio of sigma bonds and pi bonds present in benzene are: (SIBA MDCAT 2025)
Correct answer: (a) 4:1
Benzene has twelve sigma bonds and three pi bonds, a ratio of four to one.
4.What is the structure of benzene? (PMC MDCAT 2022)
Correct answer: (a) Regular, flat planar hexagon
Benzene is a flat regular hexagon with all six bonds of the same length.
5.The C-C bond length in benzene is: (PMC MDCAT 2022)
Correct answer: (a) 1.39 Angstrom
Every carbon carbon bond in benzene is $1.39\,\text{\AA}$, between a single and a double bond.
6.The unhybridized p orbitals of benzene are present in the form of _________. (PMC Practice 2021)
Correct answer: (c) In the form of a cloud above and below the benzene ring
The six unhybridized p orbitals overlap sideways into a ring of delocalized charge above and below the plane.