Created By : Rina Nayak

Reviewed By : Rajashekhar Valipishetty

Last Updated : Apr 25, 2023

With the help of the Henderson - Hasselbalch calculator, we can calculate the pH of the buffer solution. To get pH as output, we need to give inputs i.e Ka dissociation constant of an acid, molar concentration of the conjugate base in (M/mM/µM) and molar concentration of acid in(M/mM/µM) and click on the calculate button.

Conjugate Base[HA-]
Acid[HA]
Ka
pH

### Henderson Hasselbalch Equation - Definition

In chemistry, the Henderson - Hasselbalch equation is used to calculate the hydrogen ion (pH)concentration of the buffer solution.We know that the solution consists of a strong acid and a weak conjugate base or the strong base and weak conjugate acid. We can say that an acid is a proton donor and the base is a proton acceptor.

### Henderson - Hasselbalch Formula

The formula of Henderson - Hasselbalch is given below , this formula is used to calculate the pH of the buffer solution. pH = pKa + log10 ([A-]/[HA]). This equation is called the Henderson - Hasselbalch equation .

• Here, [A-] is the concentration of a base in a buffer.
• [HA] is the concentration of an acid in a buffer.
• pKa is the dissociation constant of an acid

### Henderson - Hasselbalch Equation Examples

Question 1: A mixture of 0.20M acetic acid and 0.30M sodium acetate is given. Calculate the pH of the medium if the pKa of the acetic acid is 4.76?

Given that,

pKa is the dissociation constant of an acid = 4.76

[A-] is the concentration of a base = 0.30M

[HA] is the concentration of an acid = 0.20M

Substitute the values in formula,

pH = pKa + log10 ([A-]/[HA])

Here, [A-] is the concentration of a base in a buffer.

[HA] is the concentration of an acid in a buffer.

pKa is the dissociation constant of an acid.

pH = 4.76+log(0.30/0.20)

= 4.76+log(1.5)

= 4.76+0.18

= 4.94

The pH of the given solution is 4.94

Question 2: The pH of the given solution of lactic acid and lactate is 4.30. Calculate the pKa of lactic acid and lactate are 0.020M and 0.073M respectively?

Solution:

Given that,

pH = 4.30

[A-] is the concentration of a base = 0.073M

[HA] is the concentration of an acid = 0.020M

Substitute the values in formula,

pH = pKa + log10 ([A-]/[HA])

Here,

[A-] is the concentration of a base in a buffer.

[HA] is the concentration of an acid in a buffer.

pKa is the dissociation constant of an acid.

pH = pKa + log10 ([A-]/[HA])

pH - log10 ([A-]/[HA]) = pKa

4.30 - log ( 0.073/0.020) = 4.30 - 0.56 = 3.74

The pKa of the given solution is 3.74

### How to solve the Henderson - Hasselbalch Equation?

Go through the simple steps listed below to learn how to solve the Henderson - Hasselbalch Equation. They are as follows

• Step 1: Firstly find the value of dissociation constant of an acid or base.
• Step 2: Next, find the value of log of ratio of the concentration of conjugate base to the acid concentration.
• Step 3: Add it to the pka to obtain the pH of the Solution.

### FAQ’s on Henderson- Hasselbalch Calculator

1. What is the relationship between pK and pKa?

The simple relationship between pK and pKa is pKa + pKb =14

2. What is the Henderson - Hasselbalch equation?

pH = pKa + log10 ([A-]/[HA]). This equation is called the Henderson-Hasselbalch Equation. Here, [A-] is the concentration of a base in a buffer. [HA] is the concentration of an acid in a buffer. pKa is the dissociation constant of an acid

3. The Henderson - Hasselbalch equation fails to predict accurate values for?

Henderson - Hasselbalch equation fails to predict accurate values for both strong acid and strong base.

4. Does Henderson Hasselbalch equation work for bases?

When it includes equilibrium concentrations of an acid and conjugate base, the Henderson-Hasselbalch equation is valid. Equilibrium concentrations can be far from those expected by neutralisation stoichiometry in the case of solutions containing not-so-weak acids (or not-so-weak bases).