Chapter 18, Problem 61E

Interpretation Introduction

(a)

Interpretation:

It should be shown that $\text{MnS}$ will not precipitate from this solution.

Concept introduction:

Solubility product constant, $K_{sp}$ is the equilibrium constant for a solid to be dissolved in an aqueous solution. If the reaction quotient, Q is greater than the value of $K_{sp}$, then the reaction equilibrium tends to shift left side, forming more precipitate. If reaction quotient is lower than solubility product, then precipitation will not take place. If ${\text{Q = K}}_{sp}$, then the system is in equilibrium.

Interpretation Introduction

(b)

Interpretation:

The buffer component that should be increased in concentration and the minimum value to ensure the beginning of precipitation of MnS should be determined.

Concept introduction:

The pH of a buffer system can be determined by Henderson-Hasselbalch equation as follows:

$pH=p{K}_a+\log \frac{\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$

Here, $\left[{\text{A}}^{-}\right]$ is concentration of conjugate base and $\left[\text{HA}\right]$ is the concentration of acid.