Enter the conjugate base, acid [HA], and dissociation constant into the calculator to calculate the pH of a solution.

Henderson Hasselbalch Formula

The following formula is used to calculate the pH of a solution using the Henderson Hasselbalch equation. 

pH = Kₐ + log([A⁻]/[HA])
  • Ka is the acid dissociation constant
  • A- is the molar concentration of the base in molars
  • HA is the molar concentration of the acid in molar

pH is a measure of the solutions acidity of a solution.

Henderson Hasselbalch Equation Definition

What is the Henderson Hasselbalch equation? The Henderson Hasselbalch equation is a formula used to calculate the pH (acidity) of a buffer. The equation is denoted: pH = Kₐ + log([A⁻]/[HA]).

What is a buffer? A buffer is a mixture or solution that contains a weak acid and a conjugate base. The combination of these two components, while at equilibrium,

How to calculate buffer pH?

The following is an example problem that uses the Henderson-Hasselbalch equation to determine the pH of a buffer.

  1. First, determine the acid dissociation constant. For this example, the acid dissociation constant is found to be 3.
  2. Next, determine the molar concentration of the base. The molar concentration is found to be or 3 moles per liter.
  3. Next, determine the molar concentration of the acid. For this problem, the molar concentration of the acid is found to be 4 moles per liter.
  4. Finally, calculate the buffer pH. Using the formula, the buffer pH is found to be 3 + log ( 3/4) =

Does the henderson-hasselbalch equation work for bases? The henderson-hasselbalch equation is used to find the pH values for buffer solutions, which are acid-base solutions, so the equation itself is used to bases.

When does the henderson-hasselbalch equation fail? The equation does not work in situations where the buffer solutions are highly diluted through the water.