Calculate the $[\text{H}_3\text{O}^+]$ if pH of the solution is $4.25$

If $[\text{H}_3\text{O}^+]$ of a solution is $1 \times 10^{-4}$. What is the value of pOH at $298\,\text{K}$ ?

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

A weak base is $1.3\%$ dissociated in its aqueous solution. If $K_b$ for weak base is $1.69 \times 10^{-5}$ at $298$ K. Find the concentration of aqueous solution of weak base.