Question

Which of the following have both polar and nonpolar bonds?
(A) $C_2{H}_6$
(B) $N{H}_{4}Cl$
(C) $HCl$
(D) $AlC{l}_3$

Answer 1

Hint: Electrons are unequally shared between the atoms which form polar covalent bonds, this is because of different electronegativities of atoms. On the other hand, electrons are equally shared between the atoms then they will form nonpolar covalent bonds, this is due to the same electronegativities of atoms.

Complete answer:
To answer this question we will consider each option one by one:
 $C_2{H}_6$ (Ethane)

In ethane, the difference in the electronegativities of hydrogen and carbon forming bonds in this structure is remarkably less. There is zero difference in the electronegativity of the carbon atoms which are forming bonds with each other. So ethane is a nonpolar molecule.
 $N{H}_{4}Cl$ (Ammonium chloride)

The electronegativity of nitrogen is more than hydrogen. Thus, nitrogen will have a partial negative charge as it will attract the shared pair of electrons towards itself. Hydrogen will contain a partial positive charge. Thus, $N{H}_{4}Cl$ is a polar compound with a dipole moment towards nitrogen.
The ammonium chloride also have non-polar bond this is because $N{H_4}^{+}$ has positive charge and $C{l}^{-}$ has negative charge which shows it shares equal electrons and has the same electronegativities.
 $HCl$ (Hydrogen chloride)

 $HCl$ is a polar compound because the chloride ion is more electronegative as compared to hydrogen ions. Thus, chloride ions carry partial negative dipoles and hydrogen carries partial positive dipoles.
 $AlC{l}_3$ (Aluminium chloride)

The $AlC{l}_3$ monomer has a trigonal planar shape. The dipole moments in each bond of $AlCl$ are aligned in a plane at an angle of ${120}^{\circ }$ and are therefore interrupted. It is therefore a non-polar molecule.
Thus, $N{H}_{4}Cl$ molecule has both polar and nonpolar bonds and the option $\left(b\right)$ is correct.

Note:
Covalent bonds which are in between two atoms where the electrons forming the bond are unequally distributed are known as polar bonds. Because of this the molecules have a slight electrical dipole moment where one end is slightly positive and the other is slightly negative.