Observe the following statements, which are incorrect? i. The dipole moment of $\mathrm{NH}_3$ is higher than the dipole moment of $\mathrm{NF}_3$. ii. The dipole moment of chloroform is zero. iii. Covalent bond character in $\mathrm{NaCl}$ is more compared to $\mathrm{CuCl}$.

Question

Aicharya · Accepted Answer

Statement i. The dipole moment of $\mathrm{NH}_{3}$ is higher than the dipole moment of $\mathrm{NF}_{3}$. This statement is correct. Both $\mathrm{NH}_{3}$ and $\mathrm{NF}_{3}$ have a trigonal pyramidal geometry with a lone pair of electrons on the nitrogen atom. In $\mathrm{NH}_{3}$, nitrogen is more electronegative than hydrogen, so the bond dipoles point from H to N. The dipole moment due to the lone pair on nitrogen points in the same direction as the resultant of the N-H bond dipoles, making them additive and resulting in a high net dipole moment (around 1.47 D).In $\mathrm{NF}_{3}$, fluorine is more electronegative than nitrogen, so the bond dipoles point from N to F (away from the N atom). The dipole moment due to the lone pair on nitrogen points in the opposite direction to the resultant of the N-F bond dipoles, making them subtractive and resulting in a very low net dipole moment (around 0.24 D). . Statement ii. The dipole moment of chloroform is zero. This statement is incorrect. Chloroform ($\mathrm{CHCl}_{3}$) has a tetrahedral geometry, but it is not a perfectly symmetrical molecule like carbon tetrachloride ($\mathrm{CCl}_{4}$) or methane ($\mathrm{CH}_{4}$). The bond dipoles of the three C-Cl bonds and one C-H bond do not cancel each other out due to the difference in electronegativity and the resulting asymmetrical arrangement of charges. It has a net dipole moment of approximately 1.15 D. . Statement iii. Covalent bond character in $\mathrm{NaCl}$ is more compared to $\mathrm{CuCl}$. This statement is incorrect. According to Fajan's rules, $\mathrm{CuCl}$ has a more covalent character than $\mathrm{NaCl}$. This is because the $\mathrm{Cu}^{\mathrm{+}}$ ion has a greater polarizing power than the $\mathrm{Na}^{\mathrm{+}}$ ion. $\mathrm{Cu}^{\mathrm{+}}$ has a pseudo-inert gas electron configuration ($3d^{10}$) while $\mathrm{Na}^{\mathrm{+}}$ has a noble gas configuration ($2p^{6}$). The greater polarizing power of $\mathrm{Cu}^{\mathrm{+}}$ causes a larger distortion of the electron cloud of the $\mathrm{Cl}^{\mathrm{-}}$ anion, leading to increased covalent character in $\mathrm{CuCl}$. . In summary: Statement i is correct.Statement ii is incorrect.Statement iii is incorrect.

Observe the following statements, which are incorrect? i. The dipole moment of $\mathrm{NH}_3$ is higher…

Solution