Chapter 7, Problem 65E

Interpretation Introduction

Interpretation:

The pH of a $1.00\times {10}^{-2}M$ solution of cyanide acid (HOCN) is 2.77 at 25⁰C. Ka for HOCN needs to be calculated.

Concept Introduction :

A weak acid does not completely dissociate into hydrogen ion and its conjugate base. The dissociation of an acid is represented as follows:

  $\text{HA}+{\text{H}}_{\text{2}}\text{O}\rightleftharpoons {\text{H}}_{\text{3}}{\text{O}}^{+}+{\text{A}}^{-}$

The acid dissociation constant for dissociation of an acid is represented as follows:

  $K_a=\frac{\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$