Crystals of copper sulphate are heated in a test tube for some time.
$(a)$ What is the colour of copper sulphate crystals:
$(i)$ before heating, and $(ii)$ after heating?

How is an aqueous solution with $pH = 2$ compared to an aqueous solution with $pH = 4$?

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?

As the concentration of $[H_{3}O^{+}]$ ions increases in an acidic aqueous solution,what happens to the nature of the solution?

Common salt, besides being used in the kitchen, can also be used as the raw material for making:
$(i)$ Washing soda
$(ii)$ Bleaching powder
$(iii)$ Baking soda
$(iv)$ Slaked lime

Melittin present in the bite of honeybee is a polypeptide containing $......$ amino acids.