Which of the following is acidic in nature?

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

Write true or false for the following statement:
The process of dissolving an acid or a base in water is a highly exothermic process.

Tap water conducts electricity,whereas distilled water does not. Why?

Write true or false for the following statement:
The universal indicator shows the same colour at different concentrations of hydrogen ions in a solution.

$(i)$ 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?