Enter the pH value, the concentration of the conjugate base, and the concentration of the weak acid into the pKa Calculator. The calculator will evaluate the pKa.

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## pKa Formula

The following formula is used to calculate the pKa.

pKa = pH - Log(CB/WA)

Variables:

- pKa is the pKa ( )
- pH is the pH value
- CB is the concentration of conjugate base
- WA is the concentration of weak acid

To calculate pKa, subtract the value of the log of the conjugate base concentration divide by the weak acid concentration from the pH value.

## How to Calculate pKa?

The following steps outline how to calculate the pKa.

- First, determine the pH value.
- Next, determine the concentration of conjugate base.
- Next, determine the concentration of weak acid.
- Next, gather the formula from above = pKa = pH – Log(CB/WA).
- Finally, calculate the pKa.
- After inserting the variables and calculating the result, check your answer with the calculator above.

**Example Problem:**

Use the following variables as an example problem to test your knowledge.

pH value = 5

concentration of conjugate base = .32

concentration of weak acid = .45

pKa = pH – Log(CB/WA) =** ** ?