What is the name of the apparatus used for the electrolysis of pure water?

On heating blue coloured powder of copper $(II)$ nitrate in a boiling tube,copper oxide (black),oxygen gas and a brown gas $X$ is formed.
$(a)$ Identify the type of reaction.
$(b)$ What could be the $pH$ range of an aqueous solution of the gas $X$?

What is formed when boiling sulfur reacts with dihydrogen gas?

Give reasons for the following:
$(i)$ Moist air and acidic gases are not good for some metals.
$(ii)$ Chips manufacturers usually flush bags of chips with nitrogen gas.

$A$ reddish-brown coloured metal, used in electrical wires, when powdered and heated strongly in an open china dish, its colour turns black. When hydrogen gas is passed over this black substance, it regains its original colour. Based on the above information, answer the following questions:
$(i)$ Name the metal and the black coloured substance formed.
$(ii)$ Write balanced chemical equations for both the reactions.

Why do fireflies glow at night?