Concept explainers
Interpretation:
The pH of the solutions prepared by the dissolution of the given weak bases are to be determined at
Concept introduction:
The ionization of the weak base takes place as
The formula to calculate the pOH of the solution from the concentration of hydroxide ions is
Kb is the measure of dissociation of a base and is known as the base-ionization constant, which is specific at a particular temperature.
Percent ionization is the percentage of base that gets dissociated upon addition to water. It depends on the hydroxide ion concentration.
Here,
pH is the measure of acidity of a solution, which depends on the concentration of hydronium ions and the temperature of the solution. The relationship between pH and pOH is
Answer to Problem 68QP
Solution:
(a)
(b)
Explanation of Solution
a)
Refer to Table
When a weak base is dissolved in water, only partial dissociation takes place into
The reaction of ammonia is depicted as
First, prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (2) as
Since the value of Kb is very small, the quantity of base dissociated is less. Therefore,
Thus,
Calculate the percent dissociation from equation (3) as follows:
Since the percent dissociation is less than
Now, use equation (1) to calculate the pOH of the solution:
Now, use equation (4) to calculate the pH of the solution:
Therefore, the pH of the solution is
b)
When a weak base is dissolved in water, only partial dissociation takes place into
The reaction of pyridine is depicted as follows:
First, prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (2):
Since the value of Kb is very small, the quantity of base dissociated is less. Therefore,
Thus,
Calculate the percent dissociation from equation (3):
Since the percent dissociation is less than
Now, use equation (1) to calculate the pOH of the solution:
Now, use equation (4) to calculate the pH of the solution:
Therefore, the pH of the solution is
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Chapter 16 Solutions
Package: Chemistry With Aleks 360 Access Card, 2-semester
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