pKa from Ka Calculator (Ka to pKa converter)

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The formula to calculate pKa from the Ka value is –

∴ pKa = -log10(Ka)

Ka to pKa calculator

Ka to pKa Calculator

pKa =

How to use Ka to pKa calculator?

Using the above calculator you can easily convert the Ka value to pKa.

  • Enter a Ka value in the input field labeled “Ka value =”.
  • Click the “Calculate” button.
  • The result [pKa] will be displayed in the “result” section with Step by Step solution.

Note: Most of the time the Ka value given in the problem is represented in scientific notation, for example, 5.49 × 10-8, 2.33 × 10-11, etc. 

These values can also be written as – 

⇒ 5.49 × 10-8 = 5.49e-8

⇒ 2.33 × 10-11 = 2.33e-11

So, in the “Ka to pKa calculator” put the value of Ka which is given in scientific notation as described above like [5.49e-8, 2.33e-11].

How to calculate pKa from Ka?

pKa is the negative logarithm of Ka to the base 10 as shown in the formula given below:

∴ pKa = -log10(Ka)

formula to calculate pka from ka (Ka to pKa)


Example of calculating pKa value using “Ka to pKa calculator”

Let’s say we have given the value of Ka and we need to calculate the pKa value.

For example – If the Ka value = 1.34 x 10-5, what is the [pKa] value?

As we know, the formula to convert Ka to pKa is –

∴ pKa = -log10(Ka)

Note:- As the given Ka value in scientific notation which is 1.34 x 10-5, this value can also be written as “1.34e-5”.

So, Just put this value of [Ka] in the calculator field, and press calculates button to get step by step solution.

example of converting ka to pka

∴ So, the approx pKa value for given Ka is 4.87.

Numericals based on “Converting pKa value to Ka

The Ka value for a weak acid is given to be 2.33 x 10-11. What can be the pKa value for its acidic solution?

To find the value of the pKa for the acidic solution, we can use the equation given below –

⇒ pKa = -log10(Ka)

We have given, the Ka value which is 2.33 x 10-11, it can also be written as 2.33e-11.

∴ [pKa] = -log10(2.33 x 10-11)      [∴ Put the value of Ka in “Ka to pKa calculator” as 2.33e-11]

= 10.63

So, the pKa for the given Ka value is 10.63.

The Ka for acetic acid is 1.58 x 10-5. What is the pKa value for acetic acid?

As the Ka value for acetic acid is given in the question statement. So we can substitute it into the equation given below to find pKa as follows.

⇒ pKa = -log10(Ka)

∴ pKa = -log10(1.58 x 10-5)    [∴ Put the value of Ka in “Ka to pKa converter” as 1.58e-5]

= 4.80

So, the pKa value for the given Ka of acetic acid is 4.80.

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About the author

Vishal Goyal is the founder of Topblogtenz, a comprehensive resource for students seeking guidance and support in their chemistry studies. He holds a degree in B.Tech (Chemical Engineering) and has four years of experience as a chemistry tutor. The team at Topblogtenz includes experts like experienced researchers, professors, and educators, with the goal of making complex subjects like chemistry accessible and understandable for all. A passion for sharing knowledge and a love for chemistry and science drives the team behind the website. Let's connect through LinkedIn:

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