The $pH$ of a $0.1 \ M$ solution of the acid $HA$ is $3$. The value of the ionization constant,$K_a$ of this acid is

Consider the dissociation equilibrium of the following weak acid $HA \rightleftharpoons H^{+}_{(aq)} + A^{-}_{(aq)}$. If the $pK_{a}$ of the acid is $4$, then the $pH$ of $10 \ mM$ $HA$ solution is . . . . . . . (Nearest integer)
[Given : The degree of dissociation can be neglected with respect to unity]

What is the $pH$ of $0.001 \,M$ aniline solution? The ionization constant of aniline can be taken from the table. Calculate the degree of ionization of aniline in the solution. Also,calculate the ionization constant of the conjugate acid of aniline.

Base	$K_{b}$
Dimethylamine,$(CH_{3})_{2}NH$	$5.4 \times 10^{-4}$
Triethylamine,$(C_{2}H_{5})_{3}N$	$6.45 \times 10^{-5}$
Ammonia,$NH_{3}$	$1.77 \times 10^{-5}$
Quinine	$1.10 \times 10^{-6}$
Pyridine,$C_{5}H_{5}N$	$1.77 \times 10^{-9}$
Aniline,$C_{6}H_{5}NH_{2}$	$4.27 \times 10^{-10}$
Urea,$CO(NH_{2})_{2}$	$1.3 \times 10^{-14}$

In its $0.2 \, M$ solution,an acid ionises to an extent of $60 \%$. Its hydrogen ion concentration is.....$M$

$A$ monobasic weak acid dissociates $2 \%$ in its $0.002 \ M$ solution. Calculate the dissociation constant of the weak acid.

Calculate the molar concentration of a weak monobasic acid if the acid dissociation constant $K_a = 1.8 \times 10^{-5}$ and the degree of dissociation $\alpha = 0.01$.