Chapter 15, Problem 89QRT

Interpretation Introduction

Interpretation:

The number of moles of ${\text{HNO}}_{\text{2}}$ required to prepare one liter buffer of $\text{pH}=\text{4}\text{.00}$ with $7.50\text{g}$ of ${\text{KNO}}_{\text{2}}$ has to be calculated.

Concept Introduction:

The buffer is a solution that resists any change in pH on addition of ${\text{H}}^{+}$ and ${\text{OH}}^{-}$.  An acidic buffer is made up of a weak acid and its salt.  A basic buffer is made up of a weak base and its salt.  The formula to calculate the $\text{pH}$ of the buffer is shown below.

  $\text{pH}=\text{p}{K}_{\text{a}}+\log \frac{\left[{\text{A}}^{-}\right]}{\left[\text{HA}\right]}$