Ksp vs Ka: What's the difference and how does it relate to precipitation?

Click For Summary

Discussion Overview

The discussion centers on the differences between solubility product constant (Ksp) and acid dissociation constant (Ka), particularly in the context of precipitation reactions involving metal ions in solution. Participants explore how these constants relate to the precipitation of salts when a common ion, such as chloride from NaCl, is introduced.

Discussion Character

  • Homework-related
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants explain that Ksp is a concentration constant related to solubility, while Ka pertains to acids, suggesting a similar conceptual framework but different applications.
  • One participant proposes that Ag+ will precipitate first due to the low Ksp of AgCl, although they express uncertainty about this conclusion.
  • Another participant notes that if all compounds were assumed soluble, the Ksp equation could be used to determine which salt precipitates first based on the lowest concentration of Cl- required for precipitation.
  • There is a distinction made that Ka cannot be used to determine the emergence of a new phase, whereas Ksp can be applied in that context.

Areas of Agreement / Disagreement

Participants express differing views on the application of Ksp and Ka, with some agreeing on the conceptual similarities while others highlight significant differences. The question of which compound precipitates first remains unresolved, with competing hypotheses presented.

Contextual Notes

Participants mention the need for specific concentrations and conditions to accurately apply Ksp and Ka, indicating that assumptions about solubility and concentration are critical to the discussion.

Who May Find This Useful

This discussion may be useful for students studying chemistry, particularly those interested in solubility equilibria and precipitation reactions.

muffintop
Messages
13
Reaction score
0

Homework Statement


NaCl is added slowly to a solution that is 0.010M in each Cu+, Ag+ and Au+. Ksp's are 1.9x10^-7, 1.8x10^-10 and 2.0x10^-13 respectively. Which compound will precipitate first?


Can anyone tell me how the Ksp is different from Ka? and the relationship to precipitation?
 
Physics news on Phys.org
k is just a concentration constant, sp= solubility, a = acid. same concept, different setups, however. ksp only cares about the products.


I'm guessing Ag+ precipitates first, because AgCl is insoluble. the rest are. (I'm not 100% sure, however.)

But if we assumed they were all soluble...
ksp = [.1][Cl-]

substitute stuff into that equation.
the one that gives the lowest concentration of Cl- precipitates first
 
Google solubility product.
 
cadillac said:
same concept, different setups

To some extent yes, but there are important differences. You can't use Ka to decide if the new phase emerges, you can use Ksp for that. Reaction quotient for acid solution always equals Ka, reaction quotient for solution containing weakly soluble salt doesn't have to.
 

Similar threads

What Are the Steps to Solve These Chemistry Problems?
  • · Replies 3 ·
Replies
3
Views
4K
Chem: if u can do this u = genius
  • · Replies 6 ·
Replies
6
Views
4K
What Causes Difficulty in Understanding Chemistry?
  • · Replies 1 ·
Replies
1
Views
7K
High School Gisin's ideas on time vs. special relativity—how does one reconcile them?
  • · Replies 36 ·
2
Replies
36
Views
4K
Can I get my intro Bio problems checked?
  • · Replies 1 ·
Replies
1
Views
3K
Graduate How Do Wave Properties Relate to Mass and Energy?
  • · Replies 2 ·
Replies
2
Views
3K
Newb vs Noob Guide: Understanding the Difference and How to Avoid Them
  • · Replies 22 ·
Replies
22
Views
24K
Philip Johnson's Darwin on Trial
  • · Replies 1 ·
Replies
1
Views
4K
Mathematica This Week's Finds in Mathematical Physics (Week 264)
  • · Replies 6 ·
Replies
6
Views
5K
Mathematica This Week's Finds in Mathematical Physics (Week 258)
  • · Replies 4 ·
Replies
4
Views
10K