Buffer Capacity Calculator

Your details

Choose whether to enter the acid dissociation constant as pKa or Ka.
Negative logarithm of the acid dissociation constant. For acetic acid, pKa = 4.76.
Total molar concentration of the buffer pair: C = [HA] + [A-] at the working pH.
M
The pH at which you want to evaluate the buffer capacity.
Add the water ionisation term (2.303 x ([H+] + [OH-])). Relevant at pH < 3 or > 11.
Auto-fill pKa from a common buffer. You can still adjust the value after selecting.
Buffer capacity (beta total)Moderate buffering
0.0576mol/(L pH)

Total buffer capacity including water contribution when enabled.

Buffer pair capacity (beta-buffer)0.0576mol/(L pH)
Water contribution (beta-water)0.00004mol/(L pH)
Conjugate base [A-]0.05M
Conjugate acid [HA]0.05M
[A-]/[HA] ratio1
Conjugate base (%)50%
Maximum possible beta0.0576mol/(L pH)
0.0576 mol/(L pH)
Very weak<0.005Weak0.005-0.02Moderate0.02-0.1Strong0.1+

Buffer capacity is 0.0576 mol/(L pH).

  • The pH equals the pKa, so you are at the maximum buffer capacity for this system.
  • This system is operating at 100.1% of its theoretical maximum capacity (0.0576 mol/(L pH)).
  • The [A-]/[HA] ratio is 1.00. Both components are present in meaningful amounts, which is good for practical use.

Next stepTo maximise capacity, adjust the ratio of acid to base so that pH equals pKa.

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