What is Ka1 and Ka2 in chemistry?

Home  > Chemistry Questions > Ka1 and Ka2

In chemistry, “Ka1” and “Ka2” are used to refer to the acid dissociation constants of an acid. The acid dissociation constant (Ka) is a measure of the strength of an acid in a solution.

The Ka1 and Ka2 refer to the first and second dissociation constants of a polyprotic acid, respectively. This means that a polyprotic acid can lose more than one proton, and each proton has its own dissociation constant.

For example – Carbonic acid (H2CO3) is a diprotic acid (meaning it can donate two protons) and thus it has two dissociation constants, Ka1 and Ka2.

In this case, the first dissociation constant (Ka1) represents the acidity of the first proton. It describes how H2CO3 dissociates into H+ and HCO3.

⇒  H2CO3 →  H+ + HCO3                   (Ka1 for this reaction is 4.3 x 10-7)

The second dissociation constant (Ka2) represents the acidity of the second proton. It describes how HCO3 dissociates into H+ and CO32-.

⇒  HCO3 →  H+ + CO32         (Ka2 for this reaction is 4.8 x 10-11)  

When to use Ka1 and Ka2?

The use of Ka1 and Ka2 depends on the specific acid-base equilibrium you are trying to analyze.

⇒ Ka1 is used to calculate the degree of dissociation or the acidity of the first proton in a diprotic acid like H2CO3. It can be used to determine the [H+] or the pH of a solution that contains the acid in question.

⇒ Ka2 is used to calculate the degree of dissociation or the acidity of the second proton in a diprotic acid like H2CO3. It is used when the acid has undergone the first dissociation, and we want to know the concentration of the acid after it loses the first proton.

In general, when working with a polyprotic acid, you will use the appropriate dissociation constant depending on the number of protons the acid has lost.

Did you like it?

About the author

topblogtenz author

My name is Vishal Goyal and I am the founder of Topblogtenz. I hold a degree in B.tech (Chemical Engineering) and have a strong passion for the life sciences and chemistry. As a highly qualified and experienced chemistry tutor with 4 years of experience, I possess a deep understanding of the unique challenges that students often encounter when attempting self-study in the field of chemistry. I have created this website as a comprehensive resource for those who are seeking guidance and support in their chemistry studies. I have brought together a team of experts, including experienced researchers, professors, and educators, to provide our readers with accurate and engaging information on a wide range of chemistry and science topics. Our goal is to make complex subjects like chemistry accessible and understandable for all. I hope you find the information and resources on our site helpful in your studies. Let's connect through LinkedIn: https://www.linkedin.com/in/vishal-goyal-2926a122b/

Share it...

Leave a Comment

Your email address will not be published. Required fields are marked *

Copyright © 2023 - topblogtenz.com. All rights Reserved

Scroll to Top