PKa Calculator

Calculate pKa values, pH, and concentrations for acids and bases using the Henderson-Hasselbalch equation.

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About This Tool

This pKa calculator helps you determine the acid dissociation constant (pKa) of weak acids, calculate pH from concentration values, and solve the Henderson-Hasselbalch equation. Enter known values for pKa, concentration of acid and conjugate base, or pH to calculate missing parameters. The tool provides detailed results showing the calculation method and formulas used, making it ideal for chemistry students, researchers, and professionals.

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How to Use

Select calculation type: Calculate pKa, Calculate pH, or Calculate Concentration
Enter known values in the appropriate input fields
Click the Calculate button to see results
View detailed calculation steps and formulas in the results section
Use the Reset button to clear all inputs and start over

Frequently Asked Questions

Find Quick Answers

What is pKa and how is it calculated?

pKa is the negative logarithm of the acid dissociation constant (Ka). It's calculated using the formula: pKa = -log₁₀(Ka). Lower pKa values indicate stronger acids.

How does the Henderson-Hasselbalch equation work?

The Henderson-Hasselbalch equation relates pH, pKa, and concentrations of acid and conjugate base: pH = pKa + log₁₀([A⁻]/[HA]), where [A⁻] is conjugate base concentration and [HA] is acid concentration.

Can I calculate concentration from pH and pKa?

Yes, you can calculate either acid or conjugate base concentration if you know pH, pKa, and the other concentration value using the rearranged Henderson-Hasselbalch equation.

What concentration units does the calculator use?

The calculator uses molarity (mol/L) for all concentration inputs. Results are displayed in scientific notation for very small or large values.

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