Which of the following substances does not possess a dipole moment?

Which one is a polar molecule?

Which of the following are arranged in the decreasing order of dipole moment?

Each of the following options contains a set of four molecules. Identify the option$(s)$ where all four molecules possess a permanent dipole moment at room temperature.
$(1)$ $BeCl_2, CO_2, BCl_3, CHCl_3$
$(2)$ $SO_2, C_6H_5Cl, H_2Se, BrF_5$
$(3)$ $BF_3, O_3, SF_6, XeF_6$
$(4)$ $NO_2, NH_3, POCl_3, CH_3Cl$

Which one of the following has the highest dipole moment?
$(i)$ $CH_2Cl_2$
$(ii)$ $CHCl_3$
$(iii)$ $CCl_4$

Which of the following substances has the lowest dipole moment?