Which of the following is a compound of hydrogen and oxygen?

Which type of oxide is $CO_{2}$?

During which reaction is dihydrogen gas not produced under normal conditions?

Give the formulae of the stable binary compounds that would be formed by the combination of the following pairs of elements:
$(a)$ $Mg$ and $N_{2}$
$(b)$ $Li$ and $O_{2}$
$(c)$ $Al$ and $Cl_{2}$
$(d)$ $K$ and $O_{2}$

Compound $X$ and aluminium are used to join railway tracks.
$(a)$ Identify the compound $X$.
$(b)$ Name the reaction.
$(c)$ Write down its chemical reaction.

During the extraction of iron from hematite in a blast furnace,which substance is obtained as slag?