JEE Advanced 2026 · Paper 1 · Chemistry Q3

ChemistrySingle correct+3 / -1Question 35 of 48

The correct order of dipole moments for the given species is

\ce{BF3}=\ce{NH4+}<\ce{NF3}<\ce{NH3}

\ce{BF3}<\ce{NH4+}<\ce{NF3}<\ce{NH3}

\ce{NH4+}<\ce{BF3}<\ce{NH3}<\ce{NF3}

\ce{BF3}<\ce{NH4+}<\ce{NH3}<\ce{NF3}

Answer and worked solution

Official answer: A

$\ce{BF3}$ (trigonal planar) and $\ce{NH4+}$ (tetrahedral) are symmetric: zero dipole moment.
In $\ce{NH3}$ the N-H bond dipoles point towards N, adding to the lone-pair moment: about 1.47 D.
In $\ce{NF3}$ the N-F bond dipoles point away from N, against the lone-pair moment: only about 0.23 D.

Order: $\ce{BF3}=\ce{NH4+}<\ce{NF3}<\ce{NH3}$ .

JEE Advanced 2026 · Paper 1, Chemistry question 3