This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Huckle Molecular Orbital Theory”.
1. In which year the Huckel molecular orbital theory was introduced?
a) 1973
b) 1917
c) 1920
d) 1930
View Answer
Explanation: Erich Huckel introduced the Huckel theory in 1930. This theory tells about the very simple linear combination of atomic orbitals. It states the method for the estimation of energies of molecular orbitals of π-electrons in π-delocalized molecules of organic compounds.
2. What is SOMO?
a) Singular occupied molecular orbital
b) Shortly occupied molecular orbital
c) Slightly occupied molecular orbital
d) Singly occupied molecular orbital
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Explanation: SOMO states a single occupied molecular orbital just like a HOMO( half-filled molecular orbital). The SOMO of a radical species is considered to be the highest occupied molecular orbital (HOMO).
3. Which of the following is correct decreasing order regarding resonance energy per benzene?
a) Naphthalene > Benzene > Anthracene > Phenanthrene
b) Benzene > Naphthalene > Anthracene > Phenanthrene
c) Benzene > Naphthalene > Phenanthrene > Anthracene
d) Benzene > Phenanthrene > Anthracene > Naphthalene
View Answer
Explanation: In polycyclic aromatic hydrocarbons, stability of the compound is directly proportional to the resonance energy per benzene rings. Therefore, the decreasing order of resonance energy per benzene ring is benzene > naphthalene > phenanthrene > anthracene.
4. Which of the following has the highest resonance energy?
a) Pyrrole
b) Thiophene
c) Furan
d) Benzene
View Answer
Explanation: Benzene has the highest resonance energy because of the six conjugated carbons present in the benzene. The delocalization of the p-orbital carbons on the sp2 hybridized carbons gives the aromatic qualities of benzene.
5. What is the full form of HOMO?
a) Highest occupied molecular orbitals
b) Highest occupied molecules
c) High molecular orbitals
d) High energy orbitals
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Explanation: In chemistry, HOMO is a type of molecular orbital, which is also as highest occupied molecular orbital. HOMO is the highest in energy that has electrons. The HOMO level to organic semiconductors is roughly the maximum valence bond to inorganic semiconductors and quantum dots.
6. What is the full form of LUMO?
a) Lightest occupied molecular orbital
b) Lowest unoccupied molecular orbital
c) Low occupied molecular orbital
d) Light occupy orbital
View Answer
Explanation: LUMO states the lowest occupied molecular orbital. It is a type of molecular orbital. The frontier orbitals have HOMO and LUMO collectively. These orbitals are responsible for the strength and stability of transition metal complexes.
7. The energy difference between the HOMO and LUMO is termed as HOMO-LUMO gap.
a) True
b) False
View Answer
Explanation: The given statement is true. The energy gap of the HOMO-LUMO tells about wavelengths the compound can absorb. The energy difference between HOMO-LUMO is used to predict the strength and stability of transition metal complexes, as well as the colors they produce in solution.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
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