Buffer solutions - relating volume and concentration

Click For Summary

Discussion Overview

The discussion revolves around the mathematical relationship between the concentrations of components in a buffer solution, specifically CH3COO- and CH3COOH, when mixed in varying volumes. Participants explore how to demonstrate algebraically that the ratio of concentrations at equilibrium corresponds to the ratio of their respective volumes.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant expresses confusion about the problem and seeks assistance in understanding the relationship between volume and concentration in a buffer solution.
  • Another participant suggests that the principle is straightforward but struggles to articulate the reasoning behind it, emphasizing that the substances could be any non-reactive components.
  • A participant clarifies their earlier confusion regarding the constancy of moles in the buffer solution, noting that they initially thought reactants could convert into one another, which led to their misunderstanding of equilibrium concentrations.
  • The same participant provides a detailed algebraic derivation of the concentrations at equilibrium, leading to the conclusion that the ratio of concentrations equals the ratio of volumes.
  • A later reply acknowledges the resolution of the initial question and expresses appreciation for the interaction within the forum.

Areas of Agreement / Disagreement

There is no explicit disagreement among participants, but initial confusion about the concepts indicates varying levels of understanding. The discussion appears to resolve the original question without establishing a definitive consensus on the explanation process.

Contextual Notes

Participants mention the importance of the assumption that the components do not react chemically or evaporate, which could affect the concentrations and the validity of the derived equations.

merry
Messages
44
Reaction score
0
I am really confused about how to approach the following question. Can someone please help me out?

A buffer is made by mixing CH3COO- and CH3COOH of the same concentration of 0.5M. If the volume of the former is v1 and the latter is v2, show algebraically that the following will always hold true:

[CH3COO-]/[CH3COOH] = v1/v2

where [CH3COO-] and [CH3COOH] are the concentrations at equilibrium.

Thanks a ton!
 
Chemistry news on Phys.org
Yes I find that difficult to explain.

My problem is that's so obvious I don't know how to explain it.

What's yours? :biggrin:







Well OK on second thoughts maybe. Forget your substances are what they are. They could be anything and the same result applies. As long as they don't actually do something, like react chemically. Or evaporate. Which yours will a bit so better solve this quickly!
 
Yeah, I got the answer xD I was confused because I didnt know that the number of moles remain constant. I thought some of either reactant could react to produce the other, especially since its asking for the concentrations at equilibrium. Just in case anyone was looking for the answer:

Concentration of CH3COO- at equilibrium = (0.05M)V1/(V1+V2) = [CH3COO-]
Concentration of CH3COOH at equilibrium = (0.05M)V2/(V1+V2) = [CH3COOH]

dividing the two equations,

(0.05V1)(v1+v2)/ (0.05V2)(v1+v2) = [CH3COO-]/[CH3COOH]
V1/V2 = [CH3COO-]/[CH3COOH]

tada!
@.@ wasnt at all tht hard but just confusing
 
You're welcome.

Nice to hear someone come back.

I suppose the majority do get to solutions with, without or in spite of our help, but we don't always hear.
 
xD sorry, I completely forgot that I posted this question until I saw the email when I was clearing my Inbox.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
4K
Replies
3
Views
4K
  • · Replies 4 ·
Replies
4
Views
3K
Replies
1
Views
2K
  • · Replies 3 ·
Replies
3
Views
5K
  • · Replies 20 ·
Replies
20
Views
166K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 7 ·
Replies
7
Views
3K
Replies
10
Views
12K
Replies
2
Views
17K