A
Dipole moment of $NF_3$ is greater than that of $NH_3$.
B
Three canonical forms can be drawn for $CO_3^{2-}$ ion.
C
Three resonance structures can be drawn for ozone.
D
$BF_3$ has non-zero dipole moment.
The answer is B.
Solution
Dipole moment of $NF_3$ is less than that of $NH_3$ (in $NF_3$ the lone-pair moment opposes the N–F bond moments) – incorrect.
Three equivalent canonical forms can be drawn for $CO_3^{2-}$ – correct.
Only two resonance structures can be drawn for ozone, not three – incorrect.
$BF_3$ is trigonal planar and symmetrical, so its dipole moment is zero – incorrect.
So the correct answer is: three canonical forms can be drawn for $CO_3^{2-}$ ion.
ConceptResonance structures of ozone vs carbonate ion; dipole moments of NF3, NH3, BF3
Chemical Bonding and Molecular Structure in past papers
108 questions from this chapter have appeared across 27 exam years.
