Chapter 16.5, Problem 1PE

Interpretation Introduction

Interpretation:

Using the given value of ${\text{K}}_{\text{a}}$ and concentration, the $\text{pH}$ of the given monoprotic acid has to be found.

Concept Introduction:

The acid which can dissociate only one proton is known as monoprotic acid. It can be represented as $\text{HA}$.

The $\text{pH}$ of the monoprotic acid can be determined as follows:

Step 1: Using the ICE table, determine the equilibrium concentrations of all the chemical species involved in the dissociation of the monoprotic acid.

Step 2: In the ICE table, the change in concentration is assumed as x.

Step 3: Substitute the equilibrium concentrations in the expression for the acid dissociation constant ${\text{K}}_{\text{a}}$.

Step 4: The value of x can be obtained by solving the expression of ${\text{K}}_{\text{a}}$ using approximation or quadratic equation or online equation solver.

Step 5: The value of x is equal to the concentration of the proton that is dissociated from the acid.

Step 6: The calculated concentration of the proton is used to calculate the $\text{pH}$ of the monoprotic acid solution by the following formula:

  $\text{pH}\text{=}-\log \left[{\text{H}}^{\text{+}}\right]$