Which of the following processes will increase in solution? — Ionic Equilibrium Chemistry Question

💡 Solution & Explanation

$\text{NH}_4\text{OH}$ is a weak base: $\text{NH}_4\text{OH} \rightleftharpoons \text{NH}_4^+ + \text{OH}^-$. Adding HCl neutralizes $\text{OH}^-$. Adding water dilutes the solution, lowering overall ionic concentrations including $[\text{OH}^-]$. Adding $\text{NH}_4\text{Cl}$ introduces a common ion ($\text{NH}_4^+$), suppressing dissociation and decreasing $[\text{OH}^-]$. Adding solid $\text{NH}_4\text{OH}$ increases the concentration of the weak base, shifting the equilibrium to produce more $\text{OH}^-$. Therefore, correct answer is D.