Chapter 16.3, Problem 1RQ

Interpretation Introduction

Interpretation:The truth about the amounts of ${\text{H}}^{+}$ and ${\text{OH}}^{-}$ at stoichiometric points needs to be explained.

Concept introduction:The equivalence point or stoichiometricpoint is the point in a chemical reaction when there is exactly enough acid and base to neutralize the solution.

  $\text{pH}$ is a measure of the acidity or alkalinity of a solution.

The equation for $\text{pH}$ is given by,

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

Where, ${\text{[H}}^{+}]is\text{ concentration of hydrogen ion}\text{.}$

Similarly,

  ${\text{pOH=-log[OH}}^{\text{-}}\text{]}$

Where, ${\text{[OH}}^{-}\text{] is concentration of hydroxide ion}\text{.}$

Relation between $\text{pH and pOH is pH+pOH=14}$

Answer to Problem 1RQ

The amount of ${\text{H}}^{+}$ and ${\text{OH}}^{-}$ is equal.

Explanation of Solution

In a strong acid and strong base titration, the reaction of acid and base forms a neutral solution at the equivalence point of the reaction where the number of moles of acid is equal to the number of moles of a base. Hydrogen ( ${\text{H}}^{+}$ ) and hydroxide ( ${\text{OH}}^{-}$ ) ions will react to form water, leading to a $\text{pH}$ of 7.

  $\begin{array}{c}\text{pOH=14-pH}\\ \text{=14-7}\\ \text{=7}\end{array}$

At stoichiometric point,

  $\begin{array}{c}\text{pOH=pH}\\ {\text{-log[H}}^{\text{+}}{\text{]=-log[OH}}^{\text{-}}\text{]}\\ {\text{[H}}^{\text{+}}{\text{]=[OH}}^{\text{-}}\text{]}\end{array}$

Conclusion

The amount of ${\text{H}}^{+}$ and ${\text{OH}}^{-}$ is equal.