Chapter 7, Problem 88E

Interpretation Introduction

Interpretation: The mass of ${\text{OHNH}}_{\text{2}}$ that is required to prepare 250.0 mL of a solution with pH 10.00 needs to be determined.

Concept Introduction: A base is the substance that gives ${\text{OH}}^{\text{-}}$ ions in its aqueous solution. On the basis of base dissociation, they can be classified as strong and weak base. A strong base is ionized completely and gives the respective ions.

  ${\text{BOH}}_{\text{(aq)}}\stackrel{}{\to }{\text{B}}^{+}{}_{\text{(aq)}}+{\text{OH}}^{\text{-}}{}_{\text{(aq)}}$

On the contrary, a weak base ionized partially and reaches to equilibrium.

  ${\text{B}}_{\text{(aq)}}{\text{+H}}_{\text{2}}{\text{O}}_{\text{(l}}{}_{\text{)}}\rightleftharpoons {\text{BH}}_{}^{\text{+}}{}_{\text{(aq)}}{\text{+ OH}}^{\text{-}}{}_{\text{(aq)}}$

The pH value depends on the concentration of H+ or ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ ions in the solution. The mathematical relation between pH and H+ or ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ ions can be written as:

  ${\text{pH = - log [H}}_{\text{3}}{\text{O}}^{\text{+}}]$