Which of the following substances enters our body when a red ant bites us?

Answer the following:
$(i)$ Why is Plaster of Paris written as $CaSO_{4} \cdot 1/2 H_{2}O$? How is it possible to have half a water molecule attached to $CaSO_{4}$?
$(ii)$ Why is sodium hydrogen carbonate an essential ingredient in antacids?
$(iii)$ When electricity is passed through an aqueous solution of sodium chloride,three products are obtained. Why is the process called chlor-alkali?

What range of $pH$ is considered perfect for a fertile land?

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

According to the Bronsted-Lowry acid-base theory,the substance which donates a proton $(H^+)$ to another substance is called ............

Which of the following are present in a dilute aqueous solution of hydrochloric acid?