Which among the given acids has lowest $pKa$ value

If degree of ionisation is $0.01$ of decimolar solution of weak acid $HA$ then $pKa$ of acid is

Dissociation constant for a monobasic acid is $10^{-4}$ . What is the $pH$ of the monobasic acid ? (If $\%$ dissociation $= 2\,\%$ )

For a weak acid $HA$ with dissociation constant ${10^{ - 9}},\,\,pOH$ of its $0.1 \,M$  solution is

The degree of dissociation $(\alpha )$ of $PCl_5$ obeying the equilibrium;  is $PC{l_5}\, \rightleftharpoons \,PC{l_3}\, + \,C{l_2}$ related to the pressure at equlibrium by

Ionisation constant of $CH_3COOH$ is $1.7 \times 10^{-5}$ and concentration of $H^+$ ions is $3.4 \times 10^{-4}$. Then find out initial concentration of $CH_3COOH$ Molecules