Concept explainers
Calculate the pH at
Interpretation:
The pH of the given concentration of aqueous solution that contains oxalic acid is to be determined.
Concept introduction:
The first ionization of the diprotic acid takes place as:
The second ionization of the diprotic acid takes place as:
Percent ionization is the percentage of acid that gets dissociated upon addition to water. It depends on the hydronium ion concentration.
Here,
The pH of the solution is calculated as:
Answer to Problem 89QP
Solution:
The pH of the oxalic acid solution is
Given information:
The concentration of oxalic acid
Explanation of Solution
When the oxalic acid is dissolved in water, the dissociation takes place in two steps as it is a diprotic acid. First, one proton is partially dissociated since oxalic acid is a weak acid. Thus, the concentration of
The reaction of the first proton dissociation of oxalic acid is depicted as:
First, prepare an equilibrium table and represent each of the species in terms of
Now, substitute these concentrations in equation (1) as:
Since the value of
Thus,
Calculate the percent dissociation from equation (3) as:
Since, the percent dissociation is much more than
Since, concentration cannot be negative so,
Thus,
Now, the reaction of the second proton dissociation of oxalic acid 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
Thus,
Calculate the percent dissociation from equation (3) as:
Since, the percent dissociation is much less than
Also,
Now, pH is calculated using equation (4) as:
Therefore, the pH is
The pH of
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