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Weak Base pH Calculator

This is a calculator to find values of a weak base dissociation reaction. All concentrations are measured in M (mol/liter). Values are found using the equilibrium constant formula, where the product of the concentration of products to the power of their coefficients is divided by the product of the concentration of reactants to the power of their coefficients. pKb is found by finding ten to the power of the equilibrium constant. Conversely, the equilibrium constant is used to find the pKb value by taking the negative log of the equilibrium constant value entered. The pOH value is found by taking the negative log of weak base product. This calculator can be used to fill in values of an ICE table, find the equilibrium constant of the reaction and equilibrium concentration of reactant, as well as the resulting pOH of the reaction. It can also be used to convert between the equilibrium constant and pKb values.

Select which value to solve for:


 BOH B++ OH-
I (nitial)
C (hange)
E (quilibrium)

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ParameterValue
Volume of reaction (in litre, L)
Base dissociation constant ( Kb )
pKb
pOHN/A

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Additional Information

Although calculating the pH of a monoprotic acid or base is quite simple, doing so for a polyprotic compound can often be much more complex. Polyprotic acids and bases have multiple ionizable hydrogen ions or hydroxide ions per molecule, and undergo multiple dissociation steps as a result. Furthermore, they may have different dissociation constants for each ionization step, which must be accounted for when calculating pH. In order to provide an accurate pH value for polyprotic compounds, this tool takes into account each of the dissociation constants and calculates the change in H+ or OH- concentration from each dissociation step. The tool also utilizes a univariate polynomial equation to find the exact concentration change in each step, rather than assuming that any of the dissociation constants are negligible.

It should be noted that while the pH calculation performed by this tool takes into account each dissociation step for polyprotic acids and bases, the ICE table only depicts the first dissociation step. In order to get a visual representation of the change in H+ or OH- concentration from each step for a polyprotic compound, multiple ICE tables must be computed using updated initial concentration values and the corresponding Ka value for each step.



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References

This online tool may be cited as follows

MLA

"Quest Calculate™ Weak Base pH Calculator." AAT Bioquest, Inc.14 Oct2024https://www.aatbio.com/tools/weak-base-conjugate-acid-ph-pkb-calculator.

APA

AAT Bioquest, Inc. (2024October 14). Quest Calculate™ Weak Base pH Calculator. AAT Bioquest. https://www.aatbio.com/tools/weak-base-conjugate-acid-ph-pkb-calculator.
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