If $H-X$ bond length is $2 \ \mathring{A}$ and $H-X$ has dipole moment $5.12 \times 10^{-30} \ C \cdot m$,the $\%$ of covalent character of the molecule is ............. $\%$

Which pair of molecules are polar species?

The standard molar enthalpy of vaporisation $(\Delta_{vap}H^{\circ})$ of $A, B$ and $C$ liquids is $23.3, 41$ and $29 \ kJ \ mol^{-1}$ respectively. The correct order of dipole-dipole attractive forces in these liquids is

The unequal sharing of bonded pair of electrons between two atoms in a molecule causes

Given below are two statements: one is labelled as Assertion $A$ and the other is labelled as Reason $R$.
Assertion $A$: $NH_3$ and $NF_3$ molecules have a pyramidal shape with a lone pair of electrons on the nitrogen atom. The resultant dipole moment of $NH_3$ is greater than that of $NF_3$.
Reason $R$: In $NH_3$,the orbital dipole due to the lone pair is in the same direction as the resultant dipole moment of the $N-H$ bonds. $F$ is the most electronegative element.

Which of the following molecules has a zero dipole moment?