How can Kb be used to determine Ka for a conjugate base in chemistry?

  • Thread starter Thread starter lostsheep
  • Start date Start date
  • Tags Tags
    Chemistry
Click For Summary
SUMMARY

The discussion centers on the relationship between the base dissociation constant (Kb) and the acid dissociation constant (Ka) for conjugate bases in chemistry. Specifically, the formula Kw = Ka x Kb = 1 x 10^-14 is highlighted, indicating that the product of Ka and Kb for a conjugate acid-base pair equals the ion product of water. For example, given a weak base with Kb = 1.5 x 10^-9, the corresponding Ka can be calculated using the equation Ka = Kw / Kb, resulting in Ka = 6.67 x 10^-6. This relationship is crucial for understanding acid-base equilibria.

PREREQUISITES
  • Understanding of acid-base chemistry concepts
  • Familiarity with dissociation constants (Ka and Kb)
  • Knowledge of the ion product of water (Kw)
  • Basic algebra for solving equations
NEXT STEPS
  • Learn how to calculate Ka from Kb using the formula Ka = Kw / Kb
  • Study the concept of pKa and its relationship to Ka
  • Explore examples of weak acids and their conjugate bases
  • Investigate the significance of dissociation constants in chemical equilibria
USEFUL FOR

Chemistry students, educators, and anyone interested in mastering acid-base equilibria and the calculations involving dissociation constants.

lostsheep
Messages
1
Reaction score
0
Hey guys, I am new here. I am a college student that is trying to brush up on some chemistry. I am reading an old textbook that I have, and I didnt understand something.

I was wondering how some would use the Kb of a weak base, how they would determine the value of Ka for the conjugate base?

A sample problem in the book is: A weak acid has a Kb= 1.5 x 10^-9. What is the value of Ka for the conjugate base?


I have read the whole chapter over Acid & Bases, but it says this problem is on the cd-rom that is included with my book. Yet, i never received that cd when I bought my book. I have tried searching but have had no luck. Any help would be great. I am just trying to understand the relationship between Ka and Kb. Thanks again.
 
Physics news on Phys.org
Kw = Ka x Kb = 1 x 10^-14
 
K is called a dissociation constant

What K states is that there is a certain amount of dissociation at any given time, and almost everything has one of these numbers. Something like lead chloride will have a K value to say how soluble it is. Here you are talking about water, and K relates to water breaking from HOH into H and OH. For water, the dissociation constant is 10^-14.

[H^+] * [OH^-] = 10^{-14}

K_A * K_B = 10^{-14}

pK_A + pK_B = 14
 

Similar threads

Chemistry Book seems to say that we can have weak acid and weak conjugate base
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry Understanding how to calculate pH of a buffer solution
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry Are there typos in this snippet causing confusion?
  • · Replies 2 ·
Replies
2
Views
2K
Acidity of Isobutane: pKa Value & Kb Calculation
  • · Replies 2 ·
Replies
2
Views
5K
Chemistry How to take into account autoprotolysis in weak base solution?
  • · Replies 8 ·
Replies
8
Views
2K
Chemistry How to calculate pH at equivalence point using this alternative?
  • · Replies 7 ·
Replies
7
Views
2K
Chemistry How do I know whether a base is strong or not?
  • · Replies 2 ·
Replies
2
Views
2K
Chemistry Comparing methods of computing pH at equivalence point in titration
  • · Replies 4 ·
Replies
4
Views
2K
(Chemistry) Ka of unknown acid by titrations.
  • · Replies 1 ·
Replies
1
Views
3K
Chemistry Moles of a conjugate base in a buffer solution
  • · Replies 7 ·
Replies
7
Views
3K