$0.01 \ mol$ of a weak acid $HA$ $(K_{a} = 2.0 \times 10^{-6})$ is dissolved in $1.0 \ L$ of $0.1 \ M$ $HCl$ solution. The degree of dissociation of $HA$ is ............. $\times 10^{-5}$ (Round off to the Nearest Integer). [Neglect volume change on adding $HA$. Assume degree of dissociation $<< 1$]

Given below are two statements:
Statement $I$: On passing $HCl_{(g)}$ through a saturated solution of $BaCl_2$,at room temperature white turbidity appears.
Statement $II$: When $HCl$ gas is passed through a saturated solution of $NaCl$,sodium chloride is precipitated due to common ion effect.
In the light of the above statements,choose the most appropriate answer from the options given below:

What is the solubility of $Ag_2CO_3$ in $0.1 \, M \, Na_2CO_3$? The solubility product $(K_{sp})$ of $Ag_2CO_3$ at the same temperature is $4 \times 10^{-13}$.

Assertion $(A) :-$ When a small amount of strong acid or strong base is added to pure water,its $pH$ undergoes a change.
Reason $(R) :-$ Addition of an acid or base increases the degree of ionisation of water.

The solubility of $AgCl$ is least in which of the following solutions?

The solubility of $AgI$ in $NaI$ is less than that in pure water because ................