In $BF_3$ molecule:

What is the correct increasing order of $C-O$ bond length in $CO$,$CO_3^{2-}$,and $CO_2$?

Compare the relative stability of the following resonating structures:

Which of the following can show resonance?

Which of the following compounds will not exist as a resonance hybrid? Give a reason for your answer.
$(a)$ $CH_3OH$
$(b)$ $RCONH_2$
$(c)$ $CH_3CH=CHCH_2NH_2$

Resonance in $X_2Y$ can be represented as shown in the image. The enthalpy of formation of $X_2Y$ $(X \equiv X(g) + \frac{1}{2} Y = Y(g) \rightarrow X_2Y(g))$ is $80 \ kJ \ mol^{-1}$. The magnitude of resonance energy of $X_2Y$ is $......... \ kJ \ mol^{-1}$ (nearest integer value). Given: Bond energies of $X \equiv X, X=X, Y=Y$ and $X=Y$ are $940, 410, 500$ and $602 \ kJ \ mol^{-1}$ respectively. Valence $X: 3, Y: 2$.