Which of the following set of molecules will have zero dipole moment?

Which of the following is a pair of polar molecules?

1. ${\mathrm{CO}}_2$ $\mathrm{and}$ ${\mathrm{H}}_2\mathrm{O}$

2. ${\mathrm{BF}}_3$ $\mathrm{and}$ ${\mathrm{PCl}}_3$

3. ${\mathrm{SO}}_2$ $\mathrm{and}$ ${\mathrm{SCl}}_2$

4. ${\mathrm{CS}}_2$ $\mathrm{and}$ ${\mathrm{SO}}_3$

The molecule among the following having the highest dipole moment is:
1. CO₂
2. HI
3. H₂O
4. SO₂

The application of dipole moment is/are :

Which molecule among the following is non-polar?

In which of the following molecule/ion all the bonds are not equal?