Chapter 20, Problem 14PS

(a)

Interpretation Introduction

Interpretation:

The ${\text{K}}_{\text{sp}}$ value for the given sulfide should be estimated.

Concept introduction:

• ${\text{K}}_{\text{SP}}$ for a general reaction, ${\text{AB}}_{\left(s\right)}\to {\text{A}}_{\text{(aq)}}^{\text{+}}\text{+}{\text{B}}_{\text{(aq)}}^{\text{-}}$ is,

    ${\text{K}}_{\text{SP}}\text{=}\left[{\text{A}}^{\text{+}}\right]\left[{\text{B}}^{\text{-}}\right]$

• Molarity is one of the concentrations expressing terms and it is equal to the moles of solute divided by the liter of solution.

  $\text{Molarity}\text{(M)}\text{=}\frac{\text{Moles}\text{of}\text{solute}}{\text{Liters}\text{of}\text{solution}}$

• $\text{Number}\text{of}\text{moles}\text{=}\frac{\text{Mass}\text{in}\text{grams}}{\text{Molar}\text{mass}\text{of}\text{the}\text{substance}}$
• $\text{pH}\text{=}\text{-log}\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$ it is used to know about the nature of the substance, whether it  is acidic, basic or neutral.

(b)

Interpretation Introduction

Interpretation:

The change in the solubility of ${\text{Ag}}_{\text{2}}\text{S}$ when $\text{pH}$ decreases should be determined.

Concept introduction:

• The $LeChatelier’s$ principle states that the position of equilibrium will move in such a way as to counteract the change in concentration, pressure, and temperature.