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Acid Strength Comparison Calculator

Work out acid strength comparison instantly with clear inputs, formula shown and shareable results.

About Acid Strength Comparison Calculator

Acid strength is ranked by Ka, and the ratio of two Ka values says directly how much more readily one acid gives up its proton. Because pKa is logarithmic, each unit of pKa difference is a tenfold difference in Ka: acetic acid (1.8e-5) against chloroacetic acid (6.6e-4) is a 37-fold gap, about 1.56 pKa units.

Formulas

Strength ratio

ratio = Ka2 / Ka1

Logarithmic gap

dpKa = pKa1 - pKa2

Worked example

With the default values below, Acid Strength Comparison Calculator returns Second Acid Stronger By A Factor Of of 36.667. Change any input above and every figure here is recalculated in your browser.

Inputs used

Ka of the first acidminimum 0
0.000018
Ka of the second acidminimum 0
0.00066

Results

Second Acid Stronger By A Factor Of
36.667
Difference In pKa
1.564
Verdict
The second acid is stronger
pKa Of The First Acid
4.745

Step by step

  1. 1Values used
  2. 2Strength ratio
  3. 3Logarithmic gap
  4. 4Second Acid Stronger By A Factor Of= 36.667
  5. 5Difference In pKa= 1.564
  6. 6Verdict= The second acid is stronger
  7. 7pKa Of The First Acid= 4.745

Assumptions and limits

  • The result is derived only from the 2 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 3 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Is a 1 pKa unit gap significant?

Yes - it is a tenfold difference in dissociation constant, which usually shows up clearly in reaction rate and equilibrium position.

Can I compare an acid and a base this way?

Not directly. Convert the base to the Ka of its conjugate acid first, using Ka x Kb = Kw.

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