Chapter 16, Problem 16.116QP

Each of the following statements concerns a 0.10 M solution of a weak organic base, B. Briefly describe why each statement is either true or false.

1. a [B] is approximately equal to 0.10 M.
2. b [B] is much greater than [HB⁺].
3. c [H₃O⁺] is greater than [HB⁺].
4. d The pH is 13.
5. e [HB⁺] is approximately equal to [OH⁻].
6. f [OH⁻] equals 0.10 M.

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(a)

The given statement: $\text{[B]}$ is approximately equal to 0.10 M is True

Explanation of Solution

To Describe: Whether the given statement: $\text{[B]}$ is approximately equal to 0.10 M is true or false

The given statement is true.

Reason for the true statement:

The base ionization constant ${\text{K}}_b$ for the weak bases will be small.

Therefore, most of the base molecules (solute) will be present as unreacted

Approximately 1% or less of most weak bases reacts with water.

Hence, $\text{[B]}$ is approximately equal to 0.10 M

Conclusion

The given statement: $\text{[B]}$ is approximately equal to 0.10 M is True

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(b)

The given statement: $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$ is True

Explanation of Solution

To Describe: Whether the given statement: $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$ is true or false.

The given statement is true.

Reason for the true statement:

The hydrolysis reaction for the given weak base is: ${\text{B + H}}_{\text{2}}\text{O}\stackrel{}{\rightleftharpoons }{\text{ BH}}^{\text{+}}{\text{ + OH}}^{\text{-}}$

The base ionization constant ${\text{K}}_b$ for the weak bases will be small.

Very little base has reacted with water. For weak bases, most of the base is present as the molecule.

Hence, $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$

Conclusion

The given statement: $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$ is True

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(c)

The given statement: ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$ is False

Explanation of Solution

To Describe: Whether the given statement: ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$ is true or false

The given statement is false.

Reason for the false statement:

A weak base will only give basic solution. Since, this is a basic solution, the concentration of ${\text{[H}}_3{\text{O}}^{+}]$ will be very low

Therefore, ${\text{[H}}_3{\text{O}}^{+}]$ will not be greater than ${\text{[HB}}^{+}]$

Conclusion

The given statement: ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$ is False

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(d)

The given statement: The pH is 13 is False

Explanation of Solution

To Describe: Whether the given statement: The pH is 13 is true or false

The given statement is false.

Reason for the false statement:

If the given base, $\text{B}$ were a strong base, then the hydroxide ion concentration would be equal to 0.10 M and the pH would be 13.

Since, the given base is a weak base, its pH would not be equal to 13.

Conclusion

The given statement: The pH is 13 is False

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(e)

The given statement: ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$ is True

Explanation of Solution

To Describe: Whether the given statement: ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$ is true or false

The given statement is True.

Reason for the True statement:

For every weak base molecule, $\text{B}$ that reacts with water, one ${\text{BH}}^{+}$ is generated along with one ${\text{OH}}^{-}$ .

Hence, the ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$

Conclusion

The given statement: ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$ is True

Interpretation Introduction

Interpretation:

For a 0.10 M solution of a weak organic base, $\text{B}$, the reason for the given statements, either it is true or false has to be described.

1. (a) $\text{[B]}$ is approximately equal to 0.10 M
2. (b) $\text{[B]}$ is much greater than ${\text{[HB}}^{+}]$
3. (c) ${\text{[H}}_3{\text{O}}^{+}]$ is greater than ${\text{[HB}}^{+}]$
4. (d) The pH is 13
5. (e) ${\text{[HB}}^{+}]$ is approximately equal to ${\text{[OH}}^{-}]$
6. (f) ${\text{[OH}}^{-}]$ equals to 0.10 M

Concept Introduction:

The ionization in strong base will be complete whereas in weak base the ionization will take place only to a limited extent. In weak bases, most of the base molecules remain unionized at equilibrium.

pOH definition:

The pOH of a solution is defined as the negative base-10 logarithm of the hydroxide ion ${\text{[OH}}^{-}\text{]}$ concentration.

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

The strength of bases can be found based on the following,

Higher the pOH, weaker is the base

Lower the pOH, stronger is the base

Higher the ${\text{K}}_b$ value, stronger is the base

Lower the ${\text{K}}_b$ value, weaker is the base

Answer to Problem 16.116QP

For a 0.10 M solution of a weak organic base, $\text{B}$, the given statements are:

(f)

The given statement: ${\text{[OH}}^{-}]$ equals to 0.10 M is False

Explanation of Solution

To Describe: Whether the given statement: ${\text{[OH}}^{-}]$ equals to 0.10 M is true or false

The given statement is false.

Reason for the false statement:

If the given base, $\text{B}$, were a strong base, then the ${\text{OH}}^{-}$ concentration would be 0.10 M

Since, the given base is a weak base, the ${\text{OH}}^{-}$ concentration will be less than 0.10 M

Most $\text{B}$ is present as $\text{B}$, so little ${\text{OH}}^{-}$ is produced upon addition of the base to water.