Chapter 8, Problem 8.38P

8-38 What is the pH and pOH of each solution given the following values of [OH^-)? Which solutions are acidic, which are basic, and which are neutral?

(a) 10-3 M

(b) 10-1 M

(c) 10-5 M

(d) 10-7 M

Interpretation Introduction

(a)

Interpretation:

pH and pOH of 10-3 m solution and whether it is acidic, basic or neutral solution to be identified.

Concept Introduction:

pH of a solution is the negative of logarithm of hydronium ion concentration which can be shown as:

$\text{pH = - log }\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

pOH of a solution is the negative of logarithm of hydroxide ion concentration which can be shown as:

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

Where, [H₃ O⁺ ] is the hydronium ion concentration.

[OH^- ]is the hydroxide ion concentration.

The solution having pH more than 7 is considered as basic solution while the solution having pH less than 7 is considered as acidic solution.

Answer to Problem 8.38P

pOH of solution is 3, pH of solution is 11 and it is basic solution.

Explanation of Solution

Concentration of hydroxide ion.

$\begin{array}{l}\left[{\text{OH}}^{\text{-}}\right]{\text{ = 10}}^{\text{-3}}\text{M}\hfill \\ \text{pOH = - log }\left[{\text{OH}}^{\text{-}}\right]\hfill \\ \text{= - log }\left[{\text{10}}^{\text{-3}}\right]\text{ = 3}\hfill \\ \hfill \\ \text{pH = 14 – pOH}\hfill \\ \text{= 14 – 3 = 11}\hfill \end{array}$

Thus, pOH of solution is 3, pH of solution is 11 and it is basic solution.

Interpretation Introduction

(b)

Interpretation:

pH and pOH of 10-1 m solution and whether it is acidic, basic or neutral solution to be identified.

Concept Introduction:

pH of a solution is the negative of logarithm of hydronium ion concentration which can be shown as:

$\text{pH = - log }\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

pOH of a solution is the negative of logarithm of hydroxide ion concentration which can be shown as:

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

Where, [H₃ O⁺ ] is the hydronium ion concentration.

[OH^- ]is the hydroxide ion concentration.

The solution having pH more than 7 is considered as basic solution while the solution having pH less than 7 is considered as acidic solution.

Answer to Problem 8.38P

pOH of solution is 1, pH of solution is 13 and it is basic solution.

Explanation of Solution

Concentration of hydroxide ion.

$\begin{array}{l}\left[{\text{OH}}^{\text{-}}\right]{\text{ = 10}}^{\text{-1}}\text{M}\hfill \\ \text{pOH = - log }\left[{\text{OH}}^{\text{-}}\right]\hfill \\ \text{= - log }\left[{\text{10}}^{\text{-1}}\right]\text{ = 1}\hfill \\ \hfill \\ \text{pH = 14 – pOH}\hfill \\ \text{= 14 – 1= 13}\hfill \end{array}$

Thus, pOH of solution is 1, pH of solution is 13 and it is basic solution.

Interpretation Introduction

(c)

Interpretation:

pH and pOH of 10-5 m solution and whether it is acidic, basic or neutral solution to be identified.

Concept Introduction:

pH of a solution is the negative of logarithm of hydronium ion concentration which can be shown as:

$\text{pH = - log }\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

pOH of a solution is the negative of logarithm of hydroxide ion concentration which can be shown as:

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

Where, [H₃ O⁺ ] is the hydronium ion concentration.

[OH^- ]is the hydroxide ion concentration.

The solution having pH more than 7 is considered as basic solution while the solution having pH less than 7 is considered as acidic solution.

Answer to Problem 8.38P

pOH of solution is 5, pH of solution is 9 and it is basic solution.

Explanation of Solution

Concentration of hydroxide ion.

$\begin{array}{l}\left[{\text{OH}}^{\text{-}}\right]{\text{ = 10}}^{\text{-5}}\text{M}\hfill \\ \text{pOH = - log }\left[{\text{OH}}^{\text{-}}\right]\hfill \\ \text{= - log }\left[{\text{10}}^{\text{-5}}\right]\text{ = 5}\hfill \\ \hfill \\ \text{pH = 14 – pOH}\hfill \\ \text{= 14 – 5 = 9}\hfill \end{array}$

Thus, pOH of solution is 5, pH of solution is 9 and it is basic solution.

Interpretation Introduction

(d)

Interpretation:

pH and pOH of 10-7 m solution and whether it is acidic, basic or neutral solution to be identified.

Concept Introduction:

pH of a solution is the negative of logarithm of hydronium ion concentration which can be shown as:

$\text{pH = - log }\left[{\text{H}}_{\text{3}}{\text{O}}^{\text{+}}\right]$

pOH of a solution is the negative of logarithm of hydroxide ion concentration which can be shown as:

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

Where, [H₃ O⁺ ] is the hydronium ion concentration.

[OH^- ]is the hydroxide ion concentration.

The solution having pH more than 7 is considered as basic solution while the solution having pH less than 7 is considered as acidic solution.

Answer to Problem 8.38P

pOH of solution is 7, pH of solution is 7 and it is neutral solution.

Explanation of Solution

Concentration of hydroxide ion.

$\begin{array}{l}\left[{\text{OH}}^{\text{-}}\right]{\text{ = 10}}^{\text{-7}}\text{M}\hfill \\ \text{pOH = - log }\left[{\text{OH}}^{\text{-}}\right]\hfill \\ \text{= - log }\left[{\text{10}}^{\text{-7}}\right]\text{ = 7}\hfill \\ \hfill \\ \text{pH = 14 – pOH}\hfill \\ \text{= 14 – 7 = 7}\hfill \end{array}$

Thus, pOH of solution is 7, pH of solution is 7 and it is neutral solution.