Question

Given below are two statements:
Statement (I): Hydrogen bonds are weak, with 100 Kcal/mole bond energy.
Statement (II): Hydrogen bonds play an important part in determining physical properties, and stability of crystal structures.
In light of the above statements, choose the most appropriate answer from the options given below.

• A. Statement (I) is correct but Statement (II) is incorrect.
• B. Statement (I) is incorrect but Statement (II) is correct.
• C. Both Statement (I) and Statement (II) are correct.
• D. Both Statement (I) and Statement (II) are incorrect.

Hint:

Covalent bond energy is around \(100\text{ kcal/mol}\), whereas hydrogen bond energy is much weaker, typically around \(2-10\text{ kcal/mol}\).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
Hydrogen bonds are dipole-dipole attractions that occur between a hydrogen atom covalently bound to a highly electronegative atom (like O, N, or F) and another electronegative atom.

Step 2: Detailed Explanation:
- Statement (I): Hydrogen bonds are indeed classified as weak intermolecular forces compared to covalent or ionic bonds. However, their typical bond energy is very low, ranging from \(1\text{ to }10\text{ kcal/mol}\) (approx. \(4\text{ to }40\text{ kJ/mol}\)). Strong covalent bonds (like \(\text{C-H}\) or \(\text{O-H}\)) have bond energies around \(100\text{ kcal/mol}\). Therefore, stating that hydrogen bonds have \(100\text{ kcal/mol}\) bond energy is incorrect. Thus, Statement (I) is incorrect.
- Statement (II): Despite being individually weak, the collective action of hydrogen bonds is vital for determining the physical properties of water (such as high boiling point) and stabilizing the structures of ice crystals, protein secondary structures, and DNA double helices. Thus, Statement (II) is correct.

Step 3: Final Answer:
Statement (I) is incorrect but Statement (II) is correct, representing Option B.