Question

Identify the correct orders against the property mentioned:
A. H$_2$O $>$ NH$_3$ $>$ CHCl$_3$ - dipole moment
B. XeF$_4$ $>$ XeO$_3$ $>$ XeF$_2$ - number of lone pairs on central atom 
C. O–H $>$ C–H $>$ N–O - bond length 
D. N$_2$>O$_2$>H$_2$ - bond enthalpy 
Choose the correct answer from the options given below:

• A. B, D only
• B. A, C only
• C. B, C only
• D. A, D only

Hint:

The dipole moment increases with the difference in electronegativity and the molecular geometry. Lone pairs on the central atom increase as we go from simpler molecules like XeF\(_2\) to more complex ones like XeF\(_4\).

Answer 1

The Correct Option is C

Evaluation of each property and its order: - A. H\(_2\)O $>$ NH\(_3\) $>$ CHCl\(_3\) (Dipole Moment): - Water (H\(_2\)O) exhibits the highest dipole moment due to its bent molecular geometry and the significant electronegativity difference between oxygen and hydrogen. - Ammonia (NH\(_3\)) possesses a dipole moment, albeit lower than water's, attributable to a smaller electronegativity difference and a less pronounced angular geometry. - CHCl\(_3\) displays the lowest dipole moment; despite the presence of polar bonds, the chlorine atoms induce a more symmetrical charge distribution. Therefore, A is correct. - B. XeF\(_4\)>XeO\(_3\)>XeF\(_2\) (Number of Lone Pairs on Central Atom): - XeF\(_4\) has the maximum number of lone pairs on the central xenon atom (2 lone pairs). - XeO\(_3\) has 1 lone pair. - XeF\(_2\) has no lone pairs on the central atom. Therefore, B is correct. - C. O–H $>$ C–H $>$ N–O (Bond Length): - The O–H bond is the shortest, followed by the C–H bond, with the N–O bond being the longest, a consequence of varying atomic sizes and bond strengths. Therefore, C is correct. - D. N\(_2\) $>$ O\(_2\) $>$ H\(_2\) (Bond Enthalpy): - Nitrogen (N\(_2\)) possesses the highest bond enthalpy owing to the robust triple bond between nitrogen atoms. - Oxygen (O\(_2\)) exhibits a lower bond enthalpy than nitrogen, characterized by a double bond. - Hydrogen (H\(_2\)) has the lowest bond enthalpy due to the single bond connecting hydrogen atoms. Therefore, D is incorrect because bond enthalpy decreases from N\(_2\) to H\(_2\).

The correct answer is (3) B, C only.