Q1(f). Ascending order of dipole moment: NH₃, NF₃, H₂O

Answer in brief

NF₃ (0.23 D) < NH₃ (1.47 D) < H₂O (1.85 D).

Key points

• The dipole moment is the vector sum of the bond moments and the lone-pair moment, so direction matters as much as size.
• NF₃: the three N–F moments point away from N, opposite to the lone pair; they nearly cancel, leaving 0.23 D.
• NH₃: the N–H moments point towards N, the same way as the lone pair; they add, giving 1.47 D.
• H₂O: the O–H bond is more polar than N–H, and two lone pairs act along the bond resultant; the sum is the largest, 1.85 D.