Which of the following gases present in the air blackens the surface painted with white lead?

Which of the following bonds are present in silicones?

The correct order of catenation is

The catenation tendency of $C$,$Si$ and $Ge$ is in the order $Ge < Si < C$. The bond energies (in $kJ \ mol^{-1}$) of $C-C$,$Si-Si$ and $Ge-Ge$ bonds,respectively,are:

Which one of the following elements reacts with steam?

$CO + NaOH \to $