Concept explainers
Determine the percent ionization of the following solutions of formic acid at 25°C: (a) 0.016 M, (b) 5.7 × 10−4 M, (C) 1.75 M
(a)
Interpretation:
The percent ionization of the given solutions of formic acid has to be calculated
Concept Information:
Acid ionization constant
Acids ionize in water. Strong acids ionize completely whereas weak acids ionize to some limited extent.
The degree to which a weak acid ionizes depends on the concentration of the acid and the equilibrium constant for the ionization.
The ionization of a weak acid
The equilibrium expression for the above reaction is given below.
Where,
Percent ionization:
A quantitative measure of the degree of ionization is percent ionization.
For a weak, monoprotic acid
To Calculate: The percent ionization of the given solutions of phenol
The percent ionization of given 0.016 M solution of formic acid
Answer to Problem 16.55QP
Answer
The percent ionization of the given solution (a) of phenol is 10%
Explanation of Solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given formic acid solution, the concentration of hydrogen ion can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
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Initial
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|
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Change
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|
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Equilibrium
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The
The approximate value of x is 10% of 0.016, so it is probably not appropriate to have assumed that
Start by clearing the denominator and then expand the result to get:
This equation is quadratic equation of the form
For this case,
The negative solution is not physically reasonable since there is no such things as a negative concentration.
Therefore, the
Calculation of percent ionization
The percent ionization can be calculated as follows,
Therefore, the percent ionization of given 0.016 M formic acid solution is 10%
(b)
Interpretation:
The percent ionization of the given solutions of formic acid has to be calculated
Concept Information:
Acid ionization constant
Acids ionize in water. Strong acids ionize completely whereas weak acids ionize to some limited extent.
The degree to which a weak acid ionizes depends on the concentration of the acid and the equilibrium constant for the ionization.
The ionization of a weak acid
The equilibrium expression for the above reaction is given below.
Where,
Percent ionization:
A quantitative measure of the degree of ionization is percent ionization.
For a weak, monoprotic acid
To Calculate: The percent ionization of the given solutions of phenol
The percent ionization of
Answer to Problem 16.55QP
Answer
The percent ionization of the given solution (b) of phenol is 42%
Explanation of Solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given formic acid solution, the concentration of hydrogen ion can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
| |||
Initial
|
|
|
|
Change
|
|
| |
Equilibrium
|
|
|
The
The approximate value of x is 10% of 0.016, so it is probably not appropriate to have assumed that
Start by clearing the denominator and then expand the result to get:
This equation is quadratic equation of the form
For this case,
The negative solution is rejected.
Therefore, the
Calculation of percent ionization
The percent ionization can be calculated as follows,
Therefore, the percent ionization of given 0.016 M formic acid solution is 42%
(c)
Interpretation:
The percent ionization of the given solutions of formic acid has to be calculated
Concept Information:
Acid ionization constant
Acids ionize in water. Strong acids ionize completely whereas weak acids ionize to some limited extent.
The degree to which a weak acid ionizes depends on the concentration of the acid and the equilibrium constant for the ionization.
The ionization of a weak acid
The equilibrium expression for the above reaction is given below.
Where,
Percent ionization:
A quantitative measure of the degree of ionization is percent ionization.
For a weak, monoprotic acid
To Calculate: The percent ionization of the given solutions of phenol
The percent ionization of given 1.75 M solution of formic acid
Answer to Problem 16.55QP
Answer
The percent ionization of the given solution (c) of phenol is 0.97%
Explanation of Solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given formic acid solution, the concentration of hydrogen ion can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
| |||
Initial
|
|
|
|
Change
|
|
| |
Equilibrium
|
|
|
The
Assuming that x is small compared to 1.75, we neglect it in the denominator:
Therefore, the
Calculation of percent ionization
The percent ionization can be calculated as follows,
Therefore, the percent ionization of given 0.56 M phenol solution is 0.97%
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Chapter 16 Solutions
Chemistry: Atoms First
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