Complete and balance the following chemical equations:
$(a)$ $Ca(OH)_{2} + Cl_{2} \longrightarrow$
$(b)$ $CaSO_{4} \cdot 1/2 H_{2}O + H_{2}O \longrightarrow$
$(c)$ $Na_{2}CO_{3} \cdot 10H_{2}O \xrightarrow{\text{air}} \dots$

$A$ 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?

The colour of $pH$ paper strip at the $pH$ values of $1, 7,$ and $14$ will be:

The metal salt $A$ is blue in colour. When salt $A$ is heated strongly over a burner,a substance $B$ present in it is eliminated and a white powder $C$ is left behind. When a few drops of a liquid $D$ are added to powder $C$,it becomes blue again.
$(a)$ Identify $A, B, C, D$.
$(b)$ Write the chemical equations involved.
$(c)$ Give an example of a salt which also shows the above property.

$A$ solution of a substance '$X$' is used for testing carbon dioxide. Identify '$X$'. What will be its reaction with carbon dioxide? Write a balanced equation for the reaction.

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?