Bond Energies

Concept: Triple bonds > double bonds in strength.

Step 1: Compare.

Concept:
• Hess’s law

Step 1: Formation reaction


Step 2: Using combustion data
Final Conclusion:
Option (B)

Concept:
• Standard bond enthalpy values

Step 1: Recall values
C-H
O-H
F-H
Si-H

Step 2: Match
(a)-(iv), (b)-(i), (c)-(ii), (d)-(iii) Final Conclusion:
Option (D)

Step 1: Understanding the Concept:
Bond lengths are characteristic physical properties of molecules determined experimentally (e.g., via spectroscopy or X-ray crystallography). This question tests direct factual recall of structural parameters for a fundamental organic molecule, methanol ( ).
Step 2: Key Formula or Approach:
There is no calculation required here; the approach relies entirely on recalling standard textbook data regarding the molecular geometry of alcohols.
Step 3: Detailed Explanation:
In a molecule of methanol ( ):
- The oxygen atom is hybridized.
- It forms a single bond with carbon ( ) and a single bond with hydrogen ( ).
- The standard experimentally determined bond length for the carbon-oxygen ( ) bond in methanol is approximately 142 pm.
- The standard experimentally determined bond length for the highly polar oxygen-hydrogen ( ) bond is significantly shorter, approximately 96 pm.
Looking at the options provided, 96 pm exactly matches the standard value for the bond. Values like 141 pm or 145 pm would be much closer to the bond length or a bond length respectively.
Step 4: Final Answer:
The bond length in methanol is 96 pm.