KCET 2014 Chemistry Solved Paper

We know Bond order ∝‌

1

‌ Bond length ‌

CO molecule have 3 bonds between C and O.
C

←

=

O
CO2 molecule have 2 double bonds between C and O
O=C=O
CO32− ion have 3 partial double bonds between C and O, due to resonance.HCO2− ion also show resonance, but due to the presence of hydrogen atom attached to carbon atom it has less resonance hybrid, therefore, HCO2− ion have greater bond order than CO32−Hence, the correct decreasing order of bond length is CO32−,HCO2−,CO2,CO