The correct order of increasing $\mathrm{C}-\mathrm{O}$ bond length $\mathrm{CO}, \mathrm{CO}_{3}^{2-}, \mathrm{CO}_{2}$ is:

• Correct answer
  A

  $\mathrm{CO}<\mathrm{CO}_{2}<\mathrm{CO}_{3}^{2-}$
• B

  $\mathrm{CO}_{2}<\mathrm{CO}_{3}^{2-}<\mathrm{CO}$
• C

  $\mathrm{CO}<\mathrm{CO}_{3}^{2-}<\mathrm{CO}_{2}$
• D

  $\mathrm{CO}_{3}^{2-}<\mathrm{CO}_{3}<\mathrm{CO}$

Solution

$\mathrm{C} \equiv \mathrm{Ohas}$ lowest bond length due to highest bond order. $\mathrm{O}=\mathrm{C}=\mathrm{O}$ has second lowest bond length due to double bond.
has highest has bond length due to lowest bond order which is due to resonance.

Hence, the correct answer is option: 'A'.