Write a note on carbon monoxide.

Match List I with List II

Choose the correct answer from the options given below :

Given below are two statements, one is labelled as Assertion A and the other is labelled as Reason R

Assertion A :- Carbon forms two important oxides $\mathrm{CO}$ and ${\mathrm{CO}}_2$. $\mathrm{CO}$ is neutral whereas ${\mathrm{CO}}_2$ is acidic in nature.

Reason R :  ${\mathrm{CO}}_2$ can combine with water in a limited way to form carbonic acid, while $\mathrm{CO}$ is sparingly soluble in water.

In the light of the above statements, choose the most appropriate answer from the options given below :-

Which of the following are unknown species?

a. ${\left[{\mathrm{SiCl}}_6\right]}^{2-}$
b. ${\left[\mathrm{C}(\mathrm{OH}{)}_6\right]}^{2-}$
c. ${\left[\mathrm{Al}(\mathrm{OH}{)}_6\right]}^{3-}$
d. ${\left[{\mathrm{BCl}}_6\right]}^{3-}$