Which among the following alloys contains mercury as one of its constituents?

Give a reason why electrical wires are coated with plastic.

Out of the two metals $P$ and $Q$, $P$ is less reactive than $Q$. Suggest an activity to arrange these metals in the order of their decreasing reactivity. Support your answer with a suitable chemical equation.

$A$ non-metal $A$ is an important constituent of our food and forms two oxides $B$ and $C$. Oxide $B$ is toxic,whereas $C$ causes global warming.
$(a)$ Identify $A$,$B$,and $C$.
$(b)$ To which Group of the Periodic Table does $A$ belong?

Which of the following metals is the most reactive?

Generally, metals react with acids to produce salt and hydrogen gas. Which of the following acids does not produce hydrogen gas when reacting with most metals (except $Mn$ and $Mg$)?