Chemistry Liquids MDCAT 2015
PMDC Verified Question 65 of 73
Which one of the following hydrogen bond is stronger than others?
A
\( \text{N}^{\delta-} - \text{H}^{\delta+} \cdots \text{N}^{\delta-} - \text{H}^{\delta+} \)
B
\( \text{O}^{\delta-} - \text{H}^{\delta+} \cdots \text{O}^{\delta-} - \text{H}^{\delta+} \)
C
\( \text{F}^{\delta-} - \text{H}^{\delta+} \cdots \text{F}^{\delta-} - \text{H}^{\delta+} \)
D
\( \text{N}^{\delta-} - \text{H}^{\delta+} \cdots \text{O}^{\delta-} - \text{H}^{\delta+} \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option C: \( \text{F}^{\delta-} - \text{H}^{\delta+} \cdots \text{F}^{\delta-} - \text{H}^{\delta+} \)
Concept:

The strength of a hydrogen bond is directly proportional to the electronegativity difference between the hydrogen atom and the highly electronegative atom it interacts with.

Formula:

$$ \text{Bond Strength} \propto \text{Electronegativity of } X $$

Solution:

  • Fluorine (F) is the most electronegative element on the periodic table (Pauling scale = 4.0).


  • The large difference in electronegativity creates a massive partial positive charge (\( \delta^+ \)) on the hydrogen atom in HF and a large partial negative (\( \delta^- \)) on the fluorine.


  • This results in the strongest electrostatic attraction between molecules among the given options.


Why other options are incorrect:

Oxygen (3.5) and Nitrogen (3.0) have lower electronegativities than Fluorine, making their respective hydrogen bonds weaker.

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