The $pK_a$ of a weak acid is $5.85$. The concentrations of the acid and its conjugate base are equal at a $pH$ of (in $.85$)

Find the $pOH$ value of $10^{-3} \ M \ NH_4OH$. Given $K_b = 10^{-5}$.

For a $0.1 \ M$ solution of a weak acid $HA$ $(K_a = 1.4 \times 10^{-5})$ in $2 \ L$ of solution,calculate the percentage of dissociation and the $pH$ of the solution.

What is the $pH$ of $10^{-1} \, M$ formic acid?

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]

In $20 \, mL$ of $0.4 \, M$ $HA$ solution,$80 \, mL$ of water is added. Assuming volume to be additive,the $pH$ of the final solution is ($K_a$ of $HA = 4 \times 10^{-7}, \log 2 = 0.3$).