What happens when a solution of an acid is mixed with a solution of a base in a test tube?
$(i)$ The temperature of the solution increases
$(ii)$ The temperature of the solution decreases
$(iii)$ The temperature of the solution remains the same
$(iv)$ Salt formation takes place

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?

Which solution will be basic?

$(a)$ Why should curd and sour substances not be kept in brass and copper vessels?

Give reasons for the following:
$(i)$ Why is it recommended that acid should be added to water and not water to acid?
$(ii)$ Why do compounds like alcohol and glucose not show acidic behavior even though they contain hydrogen?

Dry hydrogen chloride gas does not turn blue litmus red whereas hydrochloric acid does. Give one reason.