Ka Calculator
Calculate the acid dissociation constant Ka from equilibrium concentrations or pKa.
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Introduction
Ka Calculator — Calculate the acid dissociation constant Ka from equilibrium concentrations or pKa. Enter Given, [H⁺] (mol/L), [A⁻] (mol/L), [HA] (mol/L) to get an instant, accurate result.
Formula
Ka = [H⁺][A⁻] / [HA] at equilibrium for a weak acid HA ⇌ H⁺ + A⁻. Equivalently, Ka = 10^(−pKa).
Step-by-step
- Enter the Given.
- Enter the [H⁺] (mol/L).
- Enter the [A⁻] (mol/L).
- Enter the [HA] (mol/L).
- Click Calculate to see your result instantly.
Real-world example
Example: With Given = concs, [H⁺] (mol/L) = 0.001, [A⁻] (mol/L) = 0.001, [HA] (mol/L) = 0.1, the Ka Calculator gives Unknown: ka, Ka: 0.00001.
Frequently Asked Questions
What does a larger Ka mean?
A larger Ka indicates a stronger acid — it dissociates more completely, producing more H⁺ and A⁻ relative to undissociated HA.
How is Ka related to pKa?
pKa = −log₁₀(Ka), so Ka can always be recovered from pKa via Ka = 10^(−pKa), and vice versa.
What inputs does the Ka Calculator need?
You'll need to provide: Given, [H⁺] (mol/L), [A⁻] (mol/L), [HA] (mol/L). All fields use sensible defaults, so you can see a working example immediately and then adjust the values to match your own numbers.
How accurate is the Ka Calculator?
The Ka Calculator applies the formula exactly as calculated — Ka = [H⁺][A⁻] / [HA] at equilibrium for a weak acid HA ⇌ H⁺ + A⁻. Equivalently, Ka = 10^(−pKa). — so results are precise for the inputs you provide. Accuracy depends on entering correct, realistic input values.
Is the Ka Calculator free to use?
Yes, the Ka Calculator is completely free, requires no signup, and runs instantly in your browser.
About the Ka Calculator
The Ka Calculator uses a real, verifiable formula — Ka = [H⁺][A⁻] / [HA] at equilibrium for a weak acid HA ⇌ H⁺ + A⁻. Equivalently, Ka = 10^(−pKa). — so results are accurate every time, not an approximation.