Chapter 8, Problem 97P

8-107 Following are pH ranges for several human biological materials. From the pH at the midpoint of each range, calculate the corresponding [H₃O⁺]. Which materials are acidic, which are basic, and which are neutral? (a) Milk, pH 6.6-7.6

(b) Gastric contents, pH 1.0-3.0

(c) Spinal fluid, pH 7.3-7.5

(d) Saliva, pH 6.5-7.5

(e) Urine, pH 4.8-8.4

(f) Blood plasma, pH 7.35-7.45

(g) Feces, pH 4.6-8.4

(h) Bile, pH 6.8-7.0

Interpretation Introduction

(a)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

Basic.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of milk is in the range 6.6-7.6. The midpoint of the pH range of milk is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{6.6+7.6}{2}\\ \text{ = 7}\text{.1}\end{array}$

Now, we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 7.1=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-7.1)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-7.1)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }7.9\times {10}^{-8}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }7.9\times {10}^{-8}\text{M}$. Hence, the given solution is basic, as the concentration of [H₃ O⁺ ] is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(b)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\text{Acidic}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Gastric contents is in the range 1.0-3.0. The midpoint of the pH range of Gastric contents is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{1.0+3.0}{2}\\ \text{ = 2}\text{.0}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 2.0=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-2.0)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-2.0)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.0\times {10}^{-2}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.0\times {10}^{-2}\text{M}$. Hence, the given solution is acidic, as the concentration of [H₃ O⁺ ] is more than $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(c)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\text{Basic}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Spinal Fluids is in the range 7.3-7.5. The midpoint of the pH range of Spinal Fluids is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{7.3+7.5}{2}\\ \text{ = 7}\text{.4}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 7.4=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-7.4)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-7.4)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }4.0\times {10}^{-8}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }4.0\times {10}^{-8}\text{M}$. Hence, the given solution is basic, as the concentration of [H₃ O⁺ ] is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(d)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

Neutral.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the saliva is in the range 6.5-7.5. The midpoint of the pH range of saliva is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{6.5+7.5}{2}\\ \text{ = 7}\text{.0}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 7.0=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-7.0)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-7.0)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.0\times {10}^{-7}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.0\times {10}^{-7}\text{M}$. Hence, the given solution is neutral, as the concentration of [H₃ O⁺ ] is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(e)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\text{Acidic}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Urine is in the range 4.8-8.4. The midpoint of the pH range of Urine is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{4.8+8.4}{2}\\ \text{ = 6}\text{.6}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 7.0=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-6.6)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-6.6)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }2.5\times {10}^{-7}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ =}2.5\times {10}^{-7}\text{M}$. Hence, the given solution is acidic, as the concentration of [H₃ O⁺ ] is greater to $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(f)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\boxed{\text{basic}}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Blood Plasma is in the range 7.35-7.45. The midpoint of the pH range of Blood Plasma is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{7.35+7.45}{2}\\ \text{ = 7}\text{.4}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 7.4=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-7.4)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-7.4)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }4.0\times {10}^{-8}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }4.0\times {10}^{-8}\text{M}$. Hence, the given solution is basic, as the concentration of [H₃ O⁺ ] is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(g)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\boxed{\text{acidic}}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Feces is in the range 4.6-8.4. The midpoint of the pH range of Feces is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{4.6+8.4}{2}\\ \text{ = 6}\text{.5}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 6.5=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-6.5)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-6.5)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }3.2\times {10}^{-7}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }3.2\times {10}^{-7}\text{M}$. Hence, the given solution is acidic, as the concentration of [H₃ O⁺ ] is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$.

Interpretation Introduction

(h)

Interpretation:

The concentration of hydronium ion for given pH value should be calculated and it should be identified as acidic, basic or neutral.

Concept Introduction:

A substance is said to be acidic if it gives hydrogen ions in the aqueous solution and it is basic if gives hydroxide ions. In pH scale, the substances with pH below 7 or more than 0 are said to be acidic in nature and substances with pH greater than or below 14 are basic in nature.

The pH of solution can be calculated by taking negative log of hydrogen or hydronium ion concentration.

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

Here, $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is concentration of hydronium ion in the solution.

Answer to Problem 97P

$\text{Acidic}$.

Explanation of Solution

Given Information:

A solution is acidic if its pH is less than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is basic if its pH is greater than 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ is less than $\text{1}\text{.0}\times {\text{10}}^{-7}$

A solution is acidic if its pH is equal to 7 and the $\left[{\text{H}}_{\text{3}}{\text{O}}^{+}\right]$ = $\left[{\text{OH}}^{-}\right]$ is equal to $\text{1}\text{.0}\times {\text{10}}^{-7}$

The pH of the Bile is in the range 6.8-7.0. The midpoint of the pH range of Bile is given by the below formula:

$\begin{array}{l}\text{The midpoint of pH range = }\frac{6.8+7.0}{2}\\ \text{ = 6}\text{.9}\end{array}$

Now we need to determine the concentration of hydronium ion. The concentration of the hydronium ion can be calculated as shown below:

$\begin{array}{l}\text{ pH = }-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ 6.9=-\text{log}\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \text{antilog(}-6.9)=\left[{\text{H}}_3{\text{O}}^{+}\right]\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = antilog(}-6.9)\\ \left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.25\times {10}^{-7}\text{M}\end{array}$

Thus, the concentration of hydronium ion $\left[{\text{H}}_3{\text{O}}^{+}\right]\text{ = }1.25\times {10}^{-7}\text{M}$. Hence, the given solution is acidic, as the concentration of [H₃ O⁺ ] is greater than $\text{1}\text{.0}\times {\text{10}}^{-7}$.