Ka Calculator Formula

Understand the math behind the ka calculator. Each variable explained with a worked example.

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Formulas Used

Ka

ka_value = (h_conc * a_conc) / ha_conc

pKa

pka_value = -log10((h_conc * a_conc) / ha_conc)

Variables

VariableDescriptionDefault
h_conc[H+] at Equilibrium(M)0.004
a_conc[A-] at Equilibrium(M)0.004
ha_conc[HA] at Equilibrium(M)0.096

How It Works

How to Calculate Ka

Formula

Ka = [H+][A-] / [HA]

For the equilibrium: HA <-> H+ + A-

Worked Example

At equilibrium: [H+]=0.004, [A-]=0.004, [HA]=0.096 M.

h_conc = 0.004a_conc = 0.004ha_conc = 0.096
  1. 01Ka = (0.004 × 0.004) / 0.096
  2. 02Ka = 0.000016 / 0.096
  3. 03Ka = 1.67 × 10^-4
  4. 04pKa = -log10(1.67 × 10^-4) = 3.78

Frequently Asked Questions

What is Ka?

The acid dissociation constant measures the strength of a weak acid. Larger Ka means stronger acid (more dissociation).

What is pKa?

pKa = -log10(Ka). Lower pKa means stronger acid. It is more convenient for comparing acids.

Do strong acids have Ka values?

Strong acids fully dissociate, so their Ka is very large (effectively infinite). Ka is mainly used for weak acids.

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