Match the chemical substances given in Column $(A)$ with their appropriate application given in Column $(B)$.

Column $(A)$	Column $(B)$
$(A)$ Bleaching powder	$(i)$ Preparation of glass
$(B)$ Baking soda	$(ii)$ Production of $H_2$ and $Cl_2$
$(C)$ Washing soda	$(iii)$ Decolourisation
$(D)$ Sodium chloride	$(iv)$ Antacid

$(a)$ Identify the acid and the base whose combination forms the common salt that you use in your food. Write its formula and chemical name of this salt. Name the source from where it is obtained.
$(b)$ What is rock salt? Mention its colour and the reason due to which it has this colour.
$(c)$ What happens when electricity is passed through brine? Write the chemical equation for it.

Which of the following cannot be used as an antacid for the treatment of acidity?

$A$ sample of soil is mixed with water and allowed to settle. The clear supernatant solution turns the pH paper yellowish-orange. Which of the following would change the colour of this pH paper to greenish-blue?

Three beakers labelled as $A$,$B$ and $C$ each containing $25 \, mL$ of water were taken. $A$ small amount of $NaOH$,anhydrous $CuSO_4$ and $NaCl$ were added to the beakers $A$,$B$ and $C$ respectively. It was observed that there was an increase in the temperature of the solutions contained in beakers $A$ and $B$,whereas in case of beaker $C$,the temperature of the solution falls. Which one of the following statement$(s)$ is(are) correct?
$(i)$ In beakers $A$ and $B$,exothermic process has occurred.
$(ii)$ In beakers $A$ and $B$,endothermic process has occurred.
$(iii)$ In beaker $C$ exothermic process has occurred.
$(iv)$ In beaker $C$ endothermic process has occurred.

What is the number of moles of solute dissolved in $1 \ L$ of solution called?