Solubility of tartaric acid/sodium tartrate in high vs low pH

Click For Summary

Discussion Overview

The discussion revolves around the solubility of tartaric acid and sodium tartrate in solutions of varying pH levels, particularly focusing on why these compounds are more soluble in high pH solutions compared to low pH solutions. The context includes a lab experiment related to organic chemistry and the application of chemical principles such as dissociation and Le Chatelier's principle.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that the solubility difference can be explained by Le Chatelier's principle, where high H+ concentration in low pH solutions shifts equilibrium towards reactants, while high pH solutions with OH- push equilibrium towards products.
  • Another participant challenges this explanation, stating that it does not adequately clarify the solubility issue and emphasizes the need for a more comprehensive explanation.
  • A participant notes the pKa values of tartaric acid, indicating that at high pH, the acid will be doubly dissociated, which may contribute to its increased solubility.
  • There is a contention regarding the definitions of reactants and products in the context of the dissociation reaction, suggesting that the labeling is arbitrary and could lead to different interpretations.
  • One participant draws a parallel with the solubility of phenols in various bases, implying a similar trend in solubility behavior with increasing pH.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the explanation for the solubility differences, with multiple competing views and challenges to the proposed reasoning. The discussion remains unresolved regarding the adequacy of the explanations provided.

Contextual Notes

There are unresolved aspects regarding the assumptions made in the explanations, particularly concerning the definitions of reactants and products in the dissociation reaction and the implications of pKa values on solubility.

roneddy
Messages
2
Reaction score
0

Homework Statement


So we did a lab in organic chemistry where we did a resolution experiment for enantiomers and in the separatory funnel we had sodium tartrate/tartaric acid left in the aqueous phase of the funnel. It asks why this compound is more soluble in high ph solutions as compared to low ph solution.

Homework Equations


H2C4H4O6(aq) + H2O(l) = H30+(aq) + HC4H4O6-(aq) - disassociation reaction

3. The Attempt at a Solution

The only think i could think of was in terms of le chatelier's principle where you dissociate less in a low ph solution due to excess H+ already present pushing equilibrium towards the reactants, while in a high ph solution the OH- will react with the H+ pushing equilibrium towards the products.
 
Physics news on Phys.org
roneddy said:
The only think i could think of was in terms of le chatelier's principle where you dissociate less in a low ph solution due to excess H+ already present pushing equilibrium towards the reactants, while in a high ph solution the OH- will react with the H+ pushing equilibrium towards the products.
Bingo.
 
Ognib! I don't think that answer even if what it says is true is actually by itself explaining anything about the solubility..

About your formula by the way the pKas of tartaric acid are 2.9 and 4.4 so at high pH it will be doubly dissociated.
 
I really can't think of anything else that would allow it to be more soluble in high ph as compared to low ph.
 
I'm not saying it needs another explanation, I'm saying it needs an explanation. Yours does not amount to an explanation. Maybe there was one in your head and you have forgotten to write some essential part of it.

For what you say about reactants and products, Well what you call reactants and what you call products is arbitrary. Write your equation the other way round and products become reactants and vice versa. Then the same words that you use would give the opposite conclusion.
 
epenguin said:
Ognib!
Phenol solubilities in successively stronger bases, bicarbonate < carbonate < hydroxide; I say again, "Bingo."
 

Similar threads

Chemistry Finding the pH of this acid and its sodium salt solution
  • · Replies 7 ·
Replies
7
Views
3K
What happens if an acid is added to this buffer?
  • · Replies 2 ·
Replies
2
Views
5K
Understanding the Effect of pH on Benzoic Acid Solubility
  • · Replies 20 ·
Replies
20
Views
4K
How Can Ammonia Be Used to Adjust the pH of a Highly Acidic Solution?
  • · Replies 11 ·
Replies
11
Views
3K
Why amino acids as Zwitterons in solid state and ph neutral?
  • · Replies 1 ·
Replies
1
Views
4K
What Is the pH of 0.15 M Methylammonium Bromide Solution?
  • · Replies 16 ·
Replies
16
Views
34K
Will an Aqueous Solution of KBr Be Acidic, Basic, or Neutral?
  • · Replies 7 ·
Replies
7
Views
37K
Explaining Resistance in pH of Buffer: Strong vs Weak Acids
  • · Replies 5 ·
Replies
5
Views
9K
PH and the Acid Dissociation Constant
  • · Replies 1 ·
Replies
1
Views
23K
Solve Ka2 of Sulfuric Acid in Aqueous Solution
  • · Replies 2 ·
Replies
2
Views
16K