The $pH$ scale is applicable to which of the following?

Write the chemical equations for the reactions of zinc granules with:
$(a)$ Sulphuric acid
$(b)$ Hydrochloric acid
$(c)$ Aluminium chloride
$(d)$ Sodium hydroxide
$(e)$ Nitric acid

Write balanced chemical equations for the following:
$(a)$ Calcium carbonate reacts with hydrochloric acid.
$(b)$ Calcium oxychloride reacts with hydrochloric acid.
$(c)$ Sodium hydroxide reacts with zinc.

When hydrogen chloride gas is dissolved in water,what happens?

$A$ metal carbonate $X$ on reacting with an acid gives a gas which when passed through a solution $Y$ gives the carbonate back. On the other hand,a gas $G$ that is obtained at anode during electrolysis of brine is passed on dry $Y$,it gives a compound $Z$,used for disinfecting drinking water. Identify $X$,$Y$,$G$ and $Z$.

Which of the following substances is an antacid?