Concept explainers
Determine the pH and percent ionization for hydrocyanic acid (HCN) solutions of concentration (a) 0.25 M, (b) 0.0075 M, and (c) 8.3 × 10−5 M.
(a)
Interpretation:
The pH and percent ionization for the given concentrations of Hydrocyanic acid (
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
pH definition:
The concentration of hydrogen ion is measured using
The
To calculate: The pH and percent ionization of 0.25 M Hydrocyanic acid solution
Answer to Problem 12PPA
Answer
The pH of 0.25 M Hydrocyanic acid solution is 4.96
The percent ionization for 0.25 M Hydrocyanic acid is 0.0044%
Explanation of Solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given acetic acid solution, the concentration of hydrogen ions can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
| |||
Initial
|
0.25 -x 0.25-x |
|
|
Change
|
|
| |
Equilibrium
|
|
|
The
Assuming that x is small compared to 0.25, we neglect it in the denominator:
Therefore, the
Calculation of pH
The pH can be calculated as follows,
Calculation of percent ionization
The percent ionization can be calculated as follows,
(b)
Interpretation:
The pH and percent ionization for the given concentrations of Hydrocyanic acid (
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
pH definition:
The concentration of hydrogen ion is measured using
The
To calculate: The pH and percent ionization of 0.0075 M Hydrocyanic acid solution
Answer to Problem 12PPA
Answer
The pH of 0.0075 M Hydrocyanic acid solution is 5.72
The percent ionization for 0.0075 M Hydrocyanic acid is 0.026%
Explanation of Solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given acetic acid solution, the concentration of hydrogen ions can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
| |||
Initial
|
0.0075 -x 0.0075-x |
|
|
Change
|
|
| |
Equilibrium
|
|
|
The
Assuming that x is small compared to 0.0075, we neglect it in the denominator:
Therefore, the
Calculation of pH
The pH can be calculated as follows,
Calculation of percent ionization
The percent ionization can be calculated as follows,
(c)
Interpretation:
The pH and percent ionization for the given concentrations of Hydrocyanic acid (
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
pH definition:
The concentration of hydrogen ion is measured using
The
To calculate: The pH and percent ionization of 0.0075 M Hydrocyanic acid solution
Answer to Problem 12PPA
Answer
The pH of
The percent ionization for
Explanation of Solution
To calculate: The pH and percent ionization of Hydrocyanic acid solution
Calculation for finding out hydrogen ions:
From the equilibrium table for given acetic acid solution, the concentration of hydrogen ions can be found as follows,
Construct an equilibrium table and express the equilibrium concentration of each species in terms of
| |||
Initial
|
-x
|
|
|
Change
|
|
| |
Equilibrium
|
|
|
The
Assuming that x is small compared to
Therefore, the
Calculation of pH
The pH can be calculated as follows,
Calculation of percent ionization
The percent ionization can be calculated as follows,
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Chapter 16 Solutions
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