Question
Formic acid (HCO2H) is a weak acid with a Ka value of 1.80 x 10^4. What is the Kb value of its conju...
Solution
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The relationship between the acid dissociation constant (Ka), the base dissociation constant (Kb), and the ion product of water (Kw) is given by the equation:
Ka × Kb = Kw
The ion product of water (Kw) at 25 degrees Celsius is 1.0 x 10^-14.
Ka × Kb = Kw
The ion product of water (Kw) at 25 degrees Celsius is 1.0 x 10^-14.
The ion product of water (Kw) at 25 degrees Celsius is 1.0 x 10^-14.
Given that the Ka value of formic acid (HCO2H) is 1.80 x 10^-4, we can substitute these values into the equation to solve for the Kb value of its conjugate base, formate (HCO2-).
Rearranging the equation to solve for Kb gives:
Kb = Kw / Ka
Substituting the given values into this equation gives:
Kb = (1.0 x 10^-14) / (1.80 x 10^-4)
Performing the division gives a Kb value of approximately 5.56 x 10^-11 for the formate ion (HCO2-).
Therefore, the Kb value of the conjugate base of formic acid, formate (HCO2-), is approximately 5.56 x 10^-11.
This value indicates that formate is a weak base, as expected for the conjugate base of a weak acid. The Kb value can be used to calculate the pH of a solution of the formate ion, or to calculate the equilibrium concentrations of species in a solution of formate.
Given that the Ka value of formic acid (HCO2H) is 1.80 x 10^-4, we can substitute these values into the equation to solve for the Kb value of its conjugate base, formate (HCO2-).
Rearranging the equation to solve for Kb gives:
Kb = Kw / Ka
Substituting the given values into this equation gives:
Kb = (1.0 x 10^-14) / (1.80 x 10^-4)
Performing the division gives a Kb value of approximately 5.56 x 10^-11 for the formate ion (HCO2-).
Therefore, the Kb value of the conjugate base of formic acid, formate (HCO2-), is approximately 5.56 x 10^-11.
This value indicates that formate is a weak base, as expected for the conjugate base of a weak acid. The Kb value can be used to calculate the pH of a solution of the formate ion, or to calculate the equilibrium concentrations of species in a solution of formate.
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