Chapter 16, Problem 95AP

Interpretation Introduction

(a)

Interpretation:

The concentration of hydroxide ion $\left[{\text{OH}}^{-}\right]$ should be calculated. If the solution is acidic, neutral or basic should be indicated.

Concept Introduction:

The concentration of hydrogen ions in a solution determines the acidity of a solution. If concentration of hydrogen ion is more than the solution is more acetic, if it is low, solution is less acidic.

The pH of solution is defined as negative log of hydrogen ion concentration thus, it can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

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

Similarly, pOH of a solution is defined as negative log of hydroxide ion concentration thus, it can be calculated as follows:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

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

pH and pOH of a solution are related to each other as follows:

$\text{p}\text{H}+\text{p}\text{O}\text{H}=14$

In a pH scale, if the value of pH is below 7 the solution is said to be acidic in nature, if the pH value is above 7 it is said to be basic in nature. At pH 7, the solution is neutral.

Answer to Problem 95AP

$2.4\times {10}^{-8}\text{ M}$, Acidic.

Explanation of Solution

Given Information:

The concentration of hydrogen ion is $4.21\times {10}^{-7}\text{ M}$

Calculation:

From the given hydrogen ion concentration, pH of solution can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

Putting the values,

$\begin{array}{c}\text{p}\text{H}=-\text{log}\left(4.21\times {10}^{-7}\right)\\ =6.38\end{array}$

From the pH, pOH of solution can be calculated as follows:

$\text{p}\text{O}\text{H}=14-\text{p}\text{H}$

Putting the value,

$\begin{array}{c}\text{p}\text{O}\text{H}=14-6.38\\ =7.62\end{array}$

Thus, concentration of hydroxide ion will be:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

On rearranging,

$\left[{\text{OH}}^{-}\right]={10}^{-\text{pOH}}$

Putting the value,

$\begin{array}{c}\left[{\text{OH}}^{-}\right]={10}^{-7.62}\\ =2.4\times {10}^{-8}\text{ M}\end{array}$

Thus, concentration of hydroxide ion is $2.4\times {10}^{-8}\text{ M}$.

Since, pH of solution is below 7, the solution is acidic in nature.

Interpretation Introduction

(b)

Interpretation:

The concentration of hydroxide ion $\left[{\text{OH}}^{-}\right]$ should be calculated. If the solution is acidic, neutral or basic should be indicated.

Concept Introduction:

The concentration of hydrogen ions in a solution determines the acidity of a solution. If concentration of hydrogen ion is more than the solution is more acetic, if it is low, solution is less acidic.

The pH of solution is defined as negative log of hydrogen ion concentration thus, it can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

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

Similarly, pOH of a solution is defined as negative log of hydroxide ion concentration thus, it can be calculated as follows:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

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

pH and pOH of a solution are related to each other as follows:

$\text{p}\text{H}+\text{p}\text{O}\text{H}=14$

In a pH scale, if the value of pH is below 7 the solution is said to be acidic in nature, if the pH value is above 7 it is said to be basic in nature. At pH 7, the solution is neutral.

Answer to Problem 95AP

$2.88\times {10}^{-11}\text{ M}$, Acidic.

Explanation of Solution

Given Information:

The concentration of hydrogen ion is $0.00035\text{ M}$

Calculation:

From the given hydrogen ion concentration, pH of solution can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

Putting the values,

$\begin{array}{c}\text{p}\text{H}=-\text{log}\left(0.00035\right)\\ =3.46\end{array}$

From the pH, pOH of solution can be calculated as follows:

$\text{p}\text{O}\text{H}=14-\text{p}\text{H}$

Putting the value,

$\begin{array}{c}\text{p}\text{O}\text{H}=14-3.46\\ =10.54\end{array}$

Thus, concentration of hydroxide ion will be:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

On rearranging,

$\left[{\text{OH}}^{-}\right]={10}^{-\text{pOH}}$

Putting the value,

$\begin{array}{c}\left[{\text{OH}}^{-}\right]={10}^{-10.54}\\ =2.88\times {10}^{-11}\text{ M}\end{array}$

Thus, concentration of hydroxide ion is $2.88\times {10}^{-11}\text{ M}$.

Since, pH of solution is below 7, the solution is acidic in nature.

Interpretation Introduction

(c)

Interpretation:

The concentration of hydroxide ion $\left[{\text{OH}}^{-}\right]$ should be calculated. If the solution is acidic, neutral or basic should be indicated.

Concept Introduction:

The concentration of hydrogen ions in a solution determines the acidity of a solution. If concentration of hydrogen ion is more than the solution is more acetic, if it is low, solution is less acidic.

The pH of solution is defined as negative log of hydrogen ion concentration thus, it can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

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

Similarly, pOH of a solution is defined as negative log of hydroxide ion concentration thus, it can be calculated as follows:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

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

pH and pOH of a solution are related to each other as follows:

$\text{p}\text{H}+\text{p}\text{O}\text{H}=14$

In a pH scale, if the value of pH is below 7 the solution is said to be acidic in nature, if the pH value is above 7 it is said to be basic in nature. At pH 7, the solution is neutral.

Answer to Problem 95AP

$1.0\times {10}^{-7}\text{ M}$, Neutral.

Explanation of Solution

Given Information:

The concentration of hydrogen ion is $0.00000010\text{ M}$

Calculation:

From the given hydrogen ion concentration, pH of solution can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

Putting the values,

$\begin{array}{c}\text{p}\text{H}=-\text{log}\left(0.00000010\right)\\ =7\end{array}$

From the pH, pOH of solution can be calculated as follows:

$\text{p}\text{O}\text{H}=14-\text{p}\text{H}$

Putting the value,

$\begin{array}{c}\text{p}\text{O}\text{H}=14-7\\ =7.0\end{array}$

Thus, concentration of hydroxide ion will be:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

On rearranging,

$\left[{\text{OH}}^{-}\right]={10}^{-\text{pOH}}$

Putting the value,

$\begin{array}{c}\left[{\text{OH}}^{-}\right]={10}^{-7}\\ =1\times {10}^{-7}\text{ M}\end{array}$

Thus, concentration of hydroxide ion is $1.0\times {10}^{-7}\text{ M}$.

Since, pH of solution is equal to 7, the solution is neutral in nature.

Interpretation Introduction

(d)

Interpretation:

The concentration of hydroxide ion $\left[{\text{OH}}^{-}\right]$ should be calculated. If the solution is acidic, neutral or basic should be indicated.

Concept Introduction:

The concentration of hydrogen ions in a solution determines the acidity of a solution. If concentration of hydrogen ion is more than the solution is more acetic, if it is low, solution is less acidic.

The pH of solution is defined as negative log of hydrogen ion concentration thus, it can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

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

Similarly, pOH of a solution is defined as negative log of hydroxide ion concentration thus, it can be calculated as follows:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

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

pH and pOH of a solution are related to each other as follows:

$\text{p}\text{H}+\text{p}\text{O}\text{H}=14$

In a pH scale, if the value of pH is below 7 the solution is said to be acidic in nature, if the pH value is above 7 it is said to be basic in nature. At pH 7, the solution is neutral.

Answer to Problem 95AP

$1.0\times {10}^{-9}\text{ M}$, Acidic.

Explanation of Solution

Given Information:

The concentration of hydrogen ion is $9.9\times {10}^{-6}\text{ M}$

Calculation:

From the given hydrogen ion concentration, pH of solution can be calculated as follows:

$\text{p}\text{H}=-\text{log}\left[{\text{H}}^{+}\right]$

Putting the values,

$\begin{array}{c}\text{p}\text{H}=-\text{log}\left(9.9\times {10}^{-6}\right)\\ =5\end{array}$

From the pH, pOH of solution can be calculated as follows:

$\text{p}\text{O}\text{H}=14-\text{p}\text{H}$

Putting the value,

$\begin{array}{c}\text{p}\text{O}\text{H}=14-5\\ =9\end{array}$

Thus, concentration of hydroxide ion will be:

$\text{p}\text{O}\text{H}=-\text{log}\left[{\text{OH}}^{-}\right]$

On rearranging,

$\left[{\text{OH}}^{-}\right]={10}^{-\text{pOH}}$

Putting the value,

$\begin{array}{c}\left[{\text{OH}}^{-}\right]={10}^{-9}\\ =1.0\times {10}^{-9}\text{ M}\end{array}$

Thus, concentration of hydroxide ion is $1.0\times {10}^{-9}\text{ M}$.

Since, pH of solution is below 7, the solution is acidic in nature.