Which of the following substances is an antacid?

Which of the following statements is not correct?

Name the acid and base from which the following salts have been formed:
$(i)$ Sodium acetate.
$(ii)$ Ammonium chloride.

In one of the industrial processes used for the manufacture of sodium hydroxide,a gas $X$ is formed as a by-product. The gas $X$ reacts with lime water to give a compound $Y$,which is used as a bleaching agent in the chemical industry. Identify $X$ and $Y$ and provide the chemical equations for the reactions involved.

$(i)$ State the purpose of developing $pH$ scale.
$(ii)$ Mention the $pH$ range for acids.
$(iii)$ What is the $pH$ of acid rain and how it affects the aquatic life?

Write balanced chemical equations for the reaction of dilute $HCl$ with:
$(i)$ $Zn$ metal.
$(ii)$ $Na_{2}CO_{3}$.
$(iii)$ $NaOH$.