Chapter 10, Problem 10.67EP

Indicate whether each of the solutions in Problem 10-65 is acidic, basic, or neutral.

1. a. 3.5 × 10⁻³ M
2. b. 4.7 × 10⁻⁶ M
3. c. 1.1 × 10⁻⁸ M
4. d. 8.7 × 10⁻¹⁰ M

Interpretation Introduction

Interpretation:

The molar hydronium ion concentration in aqueous solutions formed with the hydroxide ion concentration of $\text{3}{\text{.5×10}}^{\text{-3}}\text{ M}$ has to be indicated as acidic, basic or neutral.

Concept Introduction:

Dissociation constant of water:

The dissociation of water can be given as

  ${\text{H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\rightleftarrows {\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$

The concentrations of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{ and OH}}^{\text{-}}$ at room temperature are $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$ each.

  ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{] = [OH}}^{\text{-}}\text{] = 1}{\text{.0×10}}^{\text{-7}}$

If concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be acidic solution.

If concentration of ${\text{OH}}^{-}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be basic solution.

Explanation of Solution

Given,

  $\begin{array}{l}\text{Hydroxide ion concentration }\text{= 3}{\text{.5×10}}^{\text{-3}}\text{ M}\\ \\ \text{Ion product constant for water = 1}\text{.0}\times {\text{10}}^{-14}\text{ M}\end{array}$

To calculate the molar hydronium ion concentration in aqueous solutions

  $\begin{array}{l}{\text{K}}_{\text{w}}{\text{=[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{][OH}}^{\text{-}}\text{]}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{{\text{K}}_{\text{w}}}{{\text{[OH}}^{\text{-}}\text{]}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{\text{1}{\text{.0×10}}^{\text{-14}}\text{M}}{\text{3}{\text{.5×10}}^{\text{-3}}\text{M}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=2}{\text{.9×10}}^{\text{-12}}\text{M}\end{array}$

The molar hydronium ion concentration in aqueous solutions with the hydroxide ion concentration of $\text{3}{\text{.5×10}}^{\text{-3}}\text{ M}$ is $\text{2}{\text{.9×10}}^{\text{-12}}\text{ M}$.

The hydronium ion concentration is $\text{2}{\text{.9×10}}^{\text{-12}}\text{ M}$.  As the concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ in aqueous solution is lesser than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, the solution is basic.

Interpretation Introduction

Interpretation:

The molar hydronium ion concentration in aqueous solutions formed with the hydroxide ion concentration of $\text{4}{\text{.7×10}}^{\text{-6}}\text{ M}$ has to be indicated as acidic, basic or neutral.

Concept Introduction:

Dissociation constant of water:

The dissociation of water can be given as

  ${\text{H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\rightleftarrows {\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$

The concentrations of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{ and OH}}^{\text{-}}$ at room temperature are $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$ each.

  ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{] = [OH}}^{\text{-}}\text{] = 1}{\text{.0×10}}^{\text{-7}}$

If concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be acidic solution.

If concentration of ${\text{OH}}^{-}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be basic solution.

Explanation of Solution

Given,

  $\begin{array}{l}\text{Hydroxide ion concentration }\text{= 4}{\text{.7×10}}^{\text{-6}}\text{ M}\\ \\ \text{Ion product constant for water = 1}\text{.0}\times {\text{10}}^{-14}\text{ M}\end{array}$

To calculate the molar hydronium ion concentration in aqueous solutions

  $\begin{array}{l}{\text{K}}_{\text{w}}{\text{=[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{][OH}}^{\text{-}}\text{]}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{{\text{K}}_{\text{w}}}{{\text{[OH}}^{\text{-}}\text{]}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{\text{1}{\text{.0×10}}^{\text{-14}}\text{M}}{\text{4}{\text{.7×10}}^{\text{-6}}\text{M}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=2}{\text{.1×10}}^{\text{-9}}\text{ M}\end{array}$

The molar hydronium ion concentration in aqueous solutions with the hydroxide ion concentration of $\text{4}{\text{.7×10}}^{\text{-6}}\text{ M}$ is $\text{2}{\text{.1×10}}^{\text{-9}}\text{ M}$.

The hydronium ion concentration is $\text{2}{\text{.1×10}}^{\text{-9}}\text{ M}$.  As the concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ in aqueous solution is lesser than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, the solution is basic.

Interpretation Introduction

Interpretation:

The molar hydronium ion concentration in aqueous solutions formed with the hydroxide ion concentration of $\text{1}{\text{.1×10}}^{\text{-8}}\text{ M}$ has to be indicated as acidic, basic or neutral.

Concept Introduction:

Dissociation constant of water:

The dissociation of water can be given as

  ${\text{H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\rightleftarrows {\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$

The concentrations of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{ and OH}}^{\text{-}}$ at room temperature are $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$ each.

  ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{] = [OH}}^{\text{-}}\text{] = 1}{\text{.0×10}}^{\text{-7}}$

If concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be acidic solution.

If concentration of ${\text{OH}}^{-}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be basic solution.

Explanation of Solution

Given,

  $\begin{array}{l}\text{Hydroxide ion concentration }\text{= 1}{\text{.1×10}}^{\text{-8}}\text{ M}\\ \\ \text{Ion product constant for water = 1}\text{.0}\times {\text{10}}^{-14}\text{ M}\end{array}$

To calculate the molar hydronium ion concentration in aqueous solutions

  $\begin{array}{l}{\text{K}}_{\text{w}}{\text{=[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{][OH}}^{\text{-}}\text{]}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{{\text{K}}_{\text{w}}}{{\text{[OH}}^{\text{-}}\text{]}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{\text{1}{\text{.0×10}}^{\text{-14}}\text{M}}{\text{1}{\text{.1×10}}^{\text{-8}}\text{M}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=9}{\text{.1×10}}^{\text{-7}}\text{ M}\end{array}$

The molar hydronium ion concentration in aqueous solutions with the hydroxide ion concentration of $\text{1}{\text{.1×10}}^{\text{-8}}\text{ M}$ is $\text{9}{\text{.1×10}}^{\text{-7}}\text{ M}$.

The hydronium ion concentration is $\text{9}{\text{.1×10}}^{\text{-7}}\text{ M}$.  As the concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ in aqueous solution is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, the solution is acidic.

Interpretation Introduction

Interpretation:

The molar hydronium ion concentration in aqueous solutions formed with the hydroxide ion concentration of $\text{8}{\text{.7×10}}^{\text{-10}}\text{ M}$ has to be indicated as acidic, basic or neutral.

Concept Introduction:

Dissociation constant of water:

The dissociation of water can be given as

  ${\text{H}}_{\text{2}}{\text{O}}_{\text{(l)}}{\text{ + H}}_{\text{2}}{\text{O}}_{\text{(l)}}\rightleftarrows {\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{}_{\text{(aq)}}{\text{ + OH}}^{\text{-}}{}_{\text{(aq)}}$

The concentrations of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{ and OH}}^{\text{-}}$ at room temperature are $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$ each.

  ${\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{] = [OH}}^{\text{-}}\text{] = 1}{\text{.0×10}}^{\text{-7}}$

If concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be acidic solution.

If concentration of ${\text{OH}}^{-}$ is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, it is said to be basic solution.

Explanation of Solution

Given,

  $\begin{array}{l}\text{Hydroxide ion concentration }\text{= 8}{\text{.7×10}}^{\text{-10}}\text{ M}\\ \\ \text{Ion product constant for water = 1}\text{.0}\times {\text{10}}^{-14}\text{ M}\end{array}$

To calculate the molar hydronium ion concentration in aqueous solutions

  $\begin{array}{l}{\text{K}}_{\text{w}}{\text{=[H}}_{\text{3}}{\text{O}}^{\text{+}}{\text{][OH}}^{\text{-}}\text{]}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{{\text{K}}_{\text{w}}}{{\text{[OH}}^{\text{-}}\text{]}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=}\frac{\text{1}{\text{.0×10}}^{\text{-14}}\text{M}}{\text{8}{\text{.7×10}}^{\text{-10}}\text{M}}\\ \\ {\text{[H}}_{\text{3}}{\text{O}}^{\text{+}}\text{]}\text{=1}{\text{.1×10}}^{\text{-5}}\text{ M}\end{array}$

The molar hydronium ion concentration in aqueous solutions with the hydroxide ion concentration of $\text{8}{\text{.7×10}}^{\text{-10}}\text{ M}$ is $\text{1}{\text{.1×10}}^{\text{-5}}\text{ M}$.

The hydronium ion concentration is $\text{1}{\text{.1×10}}^{\text{-5}}\text{ M}$.  As the concentration of ${\text{H}}_{\text{3}}{\text{O}}^{\text{+}}$ in aqueous solution is higher than $\text{1}{\text{.0×10}}^{\text{-7}}\text{ M}$, the solution is acidic.