Identify $X, Y$ and $Z$ in the following reaction: $2 CH_3Cl + X \xrightarrow[570 \ K]{Y} Z$

Which one of the following is a good conductor of electricity?

The silicate having one monovalent corner oxygen atom in each $SiO_4$ tetrahedron unit is:

Match the following:
| List-$I$ | List-$II$ |
| :--- | :--- |
| $A$. Carbon black | $I$. Electrodes in batteries |
| $B$. Graphite | $II$. Extraction of metals |
| $C$. Diamond | $III$. Abrasive |
| $D$. Activated charcoal | $IV$. Filler in automobile tyres |
| | $V$. Air conditioning system |

$[SiF_6]^{2-}$ is known whereas $[SiCl_6]^{2-}$ is not. Give possible reasons.

Identify the correct statements among the following:
$a$) $C_{60}$ molecule has $12$ five-membered rings and $20$ six-membered rings.
$b$) $H_2CO_3 / HCO_3^-$ buffer system helps to maintain $pH$ of blood between $7.26$ and $7.42$.
$c$) Graphite is used as a dry lubricant in machines running at high temperatures.