What is the best description of the carbon-oxygen bond lengths in CO-?
A. One short and two long bonds
B. One long and two short bonds
C. Three bonds of the same length
D. Three bonds of different lengths
Which allotropes contain carbon atoms with sp2 hybridization?
i) Diamond
ii) Graphite
iii) C60 fullerene
A. I and II only
B. I and III only
C. II and III only
D. I, II and III
The Correct Answer and Explanation is :
Let’s go over each question.
Question 1: Carbon-Oxygen Bond Lengths in CO⁻
The structure of CO⁻ (the carbon monoxide anion) can be understood by considering resonance. In the CO⁻ molecule, the bonding involves both a double bond and a lone pair on the carbon, which is slightly more negative due to the extra electron. The two atoms (carbon and oxygen) share electrons through covalent bonds, and the bond lengths tend to be intermediate between a single bond and a double bond due to the resonance stabilization.
The correct answer is:
C. Three bonds of the same length
Explanation:
In CO⁻, the molecule has a resonance structure where the bond order is effectively 2.5, meaning the bonding between carbon and oxygen is neither a pure double nor a pure triple bond. This results in the bonds being of the same length, as the resonance spreads the electron density evenly across the bonds, making them equivalent.
Question 2: Which Allotropes Contain Carbon Atoms with sp² Hybridization?
Allotropes of carbon have different bonding arrangements, leading to various hybridization states. Let’s review each option:
- Diamond: In diamond, each carbon atom is sp³ hybridized, forming four strong covalent bonds with neighboring carbon atoms, creating a 3D tetrahedral network. Therefore, diamond does not have sp² hybridized carbon atoms.
- Graphite: In graphite, each carbon atom forms three sigma bonds with neighboring carbon atoms, leaving one unhybridized p-orbital that overlaps to form a pi-bond. This results in sp² hybridization for the carbon atoms in graphite.
- C₆₀ Fullerene: C₆₀ fullerene (buckyballs) consists of carbon atoms arranged in a spherical structure, where each carbon is sp² hybridized. These carbon atoms form three bonds with neighboring carbons and maintain a pi-bond network.
The correct answer is:
C. II and III only
Explanation:
- Graphite has sp² hybridized carbon atoms because of the planar arrangement of atoms and the presence of pi-bonds above and below the plane.
- C₆₀ Fullerene has sp² hybridized carbon atoms as well, with each carbon forming three bonds in a structure that approximates a truncated icosahedron.
On the other hand, diamond does not contain sp² hybridized carbon atoms as its structure requires sp³ hybridization.
I hope this helps clarify the concepts for you! Let me know if you have more questions.