Chapter 7, Problem 77E

Interpretation Introduction

Interpretation: The pH and concentration of all species present in 2.0 M solution of hydrazine in water needs to be determined.

  ${\text{H}}_{\text{2}}{\text{NNH}}_{\text{2}}{}_{\text{(aq)}}{\text{+H}}_{\text{2}}{\text{O}}_{\text{(l}}{}_{\text{)}}\rightleftharpoons {\text{H}}_{\text{2}}{\text{NNH}}_{{}_{\text{3}}}^{\text{+}}{}_{\text{(aq)}}{\text{+ OH}}^{\text{-}}{}_{\text{(aq)}}$

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

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

The base dissociation constant is the ratio of concentration of product and reactant for the equilibrium reaction of weak base in solution. For the given weak base BOH, it can be written as:

  $\begin{array}{l}{\text{BOH}}_{\text{(aq)}}\rightleftharpoons {\text{OH}}^{\text{-}}{}_{\text{(aq)}}{\text{+ B}}^{+}{}_{\text{(aq)}}\\ {\text{K}}_{\text{b}}\text{=}\frac{{\text{[OH}}^{\text{-}}{\text{] [B}}^{+}\text{]}}{\text{[BOH]}}\end{array}$