Arrange the following in the decreasing order of their Dipole moments.

a. Chlorobenzene

b. 1,2-Dichlorobenzene

c. 1,3-Dichlorobenzene

d. 1,4-Dichlorobenzene.

Which of the following molecules does not exhibit dipole moment?

(i) CCl$$_4$$ (ii) CO$$_2$$ (iii) NH$$_3$$ (iv) CHCl$$_3$$ (v) H$$_2$$O (vi) CH$$_3$$$$-$$O$$-$$CH$$_3$$

Increasing order of bond order of oxygen and its ions is

The P-O bond order in PO$$_4^{3-}$$ is