Concept explainers
8-112 Consider an initial 0.040 M hypobromous acid (HOBr) solution at a certain temperature.
At equilibrium after partial dissociation, its pH is found to be 5.05. What is the acid ionization constant, Ka, for hypobromous acid at this temperature?
Interpretation:
The acid dissociation constant of hypobromous acid is to be calculated.
Concept Introduction:
Weak acids do not dissociate completely. Let HA be a weak acid. The dissociation of the weak acid can be represented by the chemical equation,
The equation for acid dissociation constant can be written from this chemical equation.
Here,
Answer to Problem 104P
The acid dissociation constant of hypobromous acid is
Explanation of Solution
Hypobromous acid is a weak acid. Hence, it do not dissociate completely. The dissociation of the given weak acid can be represented by the chemical equation,
The equation for acid dissociation constant can be written from this chemical equation.
The concentrations of each of the ions at equilibrium can be obtained from the ICE table. Where ICE represents the Initial, Change and Equilibrium concentrations of the weak acid.
The hydrogen ion concentration can be obtained from the given pH. The pH is defined as the negative logarithm of the hydrogen ion concentration.
The pH of the weak acid solution at equilibrium is 5.05. Thus, we can calculate the concentration of the hydrogen ion.
We calculated the “x” which is the concentration of hydrogen ion. The concentration of the anion is also “x”. Thus,
Now, we need to calculate the concentration of
The concentrations of the anion, hydrogen ion and hypobromous acid are used in the equation used for acid dissociation constant.
Thus, the acid dissociation constant of hypobromous acid is
Weak acids do not dissociate completely. Each weak acid has a specific dissociation constant. Here, ICE table is made from the given chemical equation. Thus, the acid dissociation constant of hypobromous acid is
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Chapter 8 Solutions
Introduction to General, Organic and Biochemistry
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- Introduction to General, Organic and BiochemistryChemistryISBN:9781285869759Author:Frederick A. Bettelheim, William H. Brown, Mary K. Campbell, Shawn O. Farrell, Omar TorresPublisher:Cengage Learning