In which of the following option/options, the order of arrangement does not agree with the variation of property indicated against it? (a) BF ₃ > NF ₃ > NH ₃ (Dipole moment) (b) HgCl ₂ > NH ₄^+ > SF ₆ (Bond angle) (c) NH ₃ (d) H - I > H - Br > H - Cl (Bond length)

Step-by-step solution

For (a), BF ₃ is a symmetrical trigonal planar molecule, so its dipole moment is zero. Between NH ₃ and NF ₃ , NH ₃ has a higher dipole moment because the orbital dipole of the lone pair and the bond dipoles of N - H bonds are in the same direction, whereas in NF ₃ , the N - F bond dipoles oppose the orbital dipole. The correct order of dipole moment is NH ₃ > NF ₃ > BF ₃ . The given order is incorrect. For (b), HgCl ₂ is linear with a bond angle of 180^ , NH ₄^+ is tetrahedral with a bond angle of 109.5^ , and SF