Chapter U4.19, Problem 3E

(a)

Interpretation Introduction

Interpretation:

The pH of a solution with [H⁺] = 1.0x10-4 M needs to be calculated

Concept Introduction:

The acidity of a solution is expressed in terms of its pH which is essentially the measure of the hydrogen ion (H⁺) concentration of that solution. Mathematically,

  $\text{pH = }-{\text{log[H}}^{\text{+}}\text{] -----(1)}$

If the pH is below 7 the solution is termed as acidic, if greater than 7 the solution is basic. A neutral solution will have a pH = 7

Answer to Problem 3E

pH = 4.0

Explanation of Solution

The given hydrogen ion concentration is as follows:

[H⁺] = 1.0x10-4 M

The pH of the solution is calculated as follows:

  $\begin{array}{l}\text{pH = }-{\text{log[H}}^{\text{+}}\text{] }\\ \text{=}-\text{log[1}\text{.0}\times {10}^{-4}\text{] = 4}\text{.0}\end{array}$

(b)

Interpretation Introduction

Interpretation:

The pH of a solution with [H⁺] = 1.0x10-12 M needs to be calculated.

Concept Introduction:

The acidity of a solution is expressed in terms of its pH which is essentially the measure of the hydrogen ion (H⁺) concentration of that solution. Mathematically,

  $\text{pH = }-{\text{log[H}}^{\text{+}}\text{] -----(1)}$

If the pH is below 7 the solution is termed as acidic, if greater than 7 the solution is basic. A neutral solution will have a pH = 7

Answer to Problem 3E

pH = 12.0

Explanation of Solution

The hydrogen ion concentration is given as follows:

[H⁺] = 1.0x10-12 M

The pH of the solution is calculated as follows:

  $\begin{array}{l}\text{pH = }-{\text{log[H}}^{\text{+}}\text{] }\\ \text{=}-\text{log[1}\text{.0}\times {10}^{-12}\text{] = 12}\text{.0}\end{array}$

(c)

Interpretation Introduction

Interpretation:

The pH of a solution with [OH^-] = 1.0x10-8 M needs to be calculated

Concept Introduction:

The acidity of a solution is expressed in terms of its pH which is essentially the measure of the hydrogen ion (H⁺) concentration of that solution. Mathematically,

  ${\text{pH = -log[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{] -----(1)}$

If the pH is below 7 the solution is termed as acidic, if greater than 7 the solution is basic. A neutral solution will have a pH = 7

The pH and pOH are related by the following equation:

  $\text{pH + pOH = 14 -----(2)}$

Where:

  $\text{pOH = }-{\text{log[OH}}^{-}\text{] -----(3)}$

  $$

Answer to Problem 3E

pH = 6.0

Explanation of Solution

The given hydroxide ion concentration is as follows:

[OH^-] = 1.0x10-8 M

The value of pOH can be calculated as follows:

  $\begin{array}{l}\text{pOH = }-{\text{log[OH}}^{-}\text{]}\\ \text{=}-\text{log[1}\text{.0}\times {10}^{-8}\text{] = 8}\text{.0}\end{array}$

From calculated value of pOH, pH can be calculated as follows:

  $\begin{array}{l}\text{pH = 14}-\text{ pOH }\\ \text{= 14}\text{.0 }-8.0=6.0\end{array}$