Question

The CORRECT statements about the structures of $H_2O_2, O_2F_2$ and $OF_2$ is/are:

• A. $H_2O_2, O_2F_2, OF_2$ are polar compounds
• B. $d_{O-O}$ of $H_2O_2 > d_{O-O}$ of $O_2F_2$
• C. $d_{O-F}$ of $OF_2 > d_{O-F}$ of $O_2F_2$
• D. the strength of $O-O$ bond in $O_2F_2$ is greater than that of $H_2O_2$

Answer 1

Answer: (A), (B), (D)

A, B, D

Answer 2

The solution involves analyzing the structure, polarity, bond lengths, and bond strengths of the given compounds.

1. Analyze the polarity of $H_2O_2, O_2F_2, OF_2$ (Statement A):

• $H_2O_2$ (Hydrogen Peroxide): Has a non-planar "open book" structure (H-O-O-H). The O-H bonds are polar, and due to the non-planar geometry, the bond dipoles do not cancel out, resulting in a net dipole moment. Thus, $H_2O_2$ is polar.
• $O_2F_2$ (Dioxygen Difluoride): Similar to $H_2O_2$, it has a non-planar "open book" structure (F-O-O-F). The O-F bonds are polar (Fluorine is more electronegative than Oxygen). Due to the non-planar geometry, the bond dipoles do not cancel out, resulting in a net dipole moment. Thus, $O_2F_2$ is polar.
• $OF_2$ (Oxygen Difluoride): Has a bent (V-shaped) structure, similar to water. The central oxygen atom has two lone pairs and forms two polar O-F bonds. The bond dipoles do not cancel out due to the bent geometry, resulting in a net dipole moment. Thus, $OF_2$ is polar.
• Conclusion for (A): All three compounds ($H_2O_2, O_2F_2, OF_2$) are polar. Statement (A) is CORRECT.

2. Compare $d_{O-O}$ of $H_2O_2$ and $O_2F_2$ (Statement B):

• $H_2O_2$: The O-O bond is a single bond. The experimental O-O bond length is approximately 1.48 Å.
• $O_2F_2$: The O-O bond is also formally a single bond. However, due to the high electronegativity of fluorine, electron density is strongly withdrawn from the oxygen atoms. This reduces the lone pair-lone pair repulsion between the oxygen atoms and increases the effective nuclear charge, leading to an unusually short and strong O-O bond. The experimental O-O bond length is approximately 1.22 Å, which is even shorter than the O=O double bond in $O_2$ (1.21 Å).
• Comparison: $1.48 \text{ Å} (H_2O_2) > 1.22 \text{ Å} (O_2F_2)$.
• Conclusion for (B): Statement (B) is CORRECT.

3. Compare $d_{O-F}$ of $OF_2$ and $O_2F_2$ (Statement C):

• $OF_2$: The O-F bond in $OF_2$ is a single bond. The experimental O-F bond length is approximately 1.41 Å.
• $O_2F_2$: The O-F bond in $O_2F_2$ is also a single bond. The experimental O-F bond length is approximately 1.58 Å.
• Comparison: $1.41 \text{ Å} (OF_2) < 1.58 \text{ Å} (O_2F_2)$.
• Therefore, $d_{O-F}$ of $OF_2$ is not greater than $d_{O-F}$ of $O_2F_2$.
• Conclusion for (C): Statement (C) is INCORRECT.

4. Compare the strength of $O-O$ bond in $O_2F_2$ and $H_2O_2$ (Statement D):

• Bond strength is inversely related to bond length. A shorter bond is generally stronger.
• From the analysis in (B), we found that $d_{O-O}$ of $O_2F_2$ (1.22 Å) is significantly shorter than $d_{O-O}$ of $H_2O_2$ (1.48 Å).
• Since the O-O bond in $O_2F_2$ is much shorter, it indicates that it is stronger than the O-O bond in $H_2O_2$.
• Conclusion for (D): Statement (D) is CORRECT.

Final Answer: Statements (A), (B), and (D) are correct.