Which of the following is not a Lewis acid?

Which of the following species has no $p\pi - p\pi$ bond but has a bond order equal to that of $O_2$?

Among the following,the bond angle is minimum between:

What is formal charge? Explain by example.

Which of the following triatomic molecules does not exist?

$O-O$ bond length in $H_2O_2$ is $\underline{X}$ than the $O-O$ bond length in $F_2O_2$. The $O-H$ bond length in $H_2O_2$ is $Y$ than that of the $O-F$ bond in $F_2O_2$. Choose the correct option for $\underline{X}$ and $\underline{Y}$ from the given below.