Which of the following is a polar molecule?

The observed dipole moment of $HCl$ is $1.303 \ D$. This indicates that $HCl$ has $17 \%$ ionic and $83 \%$ covalent character. The bond length of $HCl$ is $1.26 \ \mathring{A}$ and the charges on $H$ and $Cl$ ions are $+e$ and $-e$. Calculate the theoretical dipole moment in $D$.

Which one of the following molecules is polar?

Both $BF_3$ and $NH_3$ are covalent molecules. However,$BF_3$ is non-polar while $NH_3$ is polar. What is the reason for this?

The dipole moments of $CCl_{4}$,$CHCl_{3}$ and $CH_{4}$ are in the order:

$(a)$ Discuss the significance/applications of dipole moment.
$(b)$ Represent diagrammatically the bond moments and the resultant dipole moment in $CO_2, NF_3$ and $CHCl_3$.