p and p Overlap

Q. Which of the following orders is correct for the bond dissociation energy of $O_2^{+},O_2,O_2^{-}$ and $O_2^{2-}$?

1. $O_2^{+}>O_2>O_2^{-}>O_2^{2-}$
2. $O_2^{+}>O_2<O_2<O_2^{2-}$
3. $O_2^{+}<O_2<O_2<O_2^{2-}$
4. $O_2^{+}>O_2>O_2^{2-}>O_2^{-}$

Q. Which is not true about metal carbonyls?

1. Here metal acts as Lewis base as well as Lewis acid
2. Here $CO$ acts as a Lewis base as well as Lewis acid
3. Here $p\pi -p\pi$ back bonding takes place
4. Here $d\pi -p\pi$ back bonding takes place

Q. Assuming $z$-orbital to be the inter-nuclear axis, which of the following overlaps is incorrect?

1. $2p_y+2p_y\to \pi 2p_y$
2. $2p_z+2p_z\to \sigma 2p_z$
3. $2p_x+2p_x\to \pi 2p_x$
4. $1s+2p_y\to \pi (1s-2p_y)$

Q. $I.CO$
$II.PC{l}_5$
$III.B{F}_3$
$IV.BC{l}_3$
$V.Si{H}_4$
$VI.Si{F}_4$
$VII.CC{l}_4$
$VIII.BeC{l}_2$
$IX.N(Si{H}_3{)}_3$
$X.H_{2}O$
The number of molecules showing back bonding among the given molecules

Q. Which of the following is the correct prediction about observed $B-F$ bond length, in $B{F}_3$ molecule?

1. The bond length is more than actual because of the large difference in electronegativity value.
2. The small bond length is due to $p\pi -p\pi$ back bonding.
3. Both $\left(a\right)$ and $\left(b\right)$
4. None of these

Q. Which of the following has the lowest 'C-O' bond strength?

1. $\left[Cr\right(CO{)}_6]$
2. $\left[Ti\right(CO{)}_6{]}^{2-}$
3. $\left[Mn\right(CO{)}_6{]}^{+}$
4. $\left[V\right(CO{)}_6{]}^{-}$

Q. Which of the following reactions is/are likely to be impossible :

1. $(C{H}_3{)}_{2}O+B{F}_3$
2. $(Si{H}_3{)}_{2}O+B{F}_3$
3. $(Si{H}_3{)}_{3}N+B{F}_3$
4. All are possible