Calculate pH of Buffer CH_3COOH & CH_3COONa

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Discussion Overview

The discussion revolves around calculating the pH of a buffer solution composed of acetic acid (CH3COOH) and sodium acetate (CH3COONa), particularly after diluting the buffer. Participants explore the necessary steps and equations to approach the problem, including the Henderson-Hasselbalch equation.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant expresses confusion about how to begin the calculation, particularly regarding the dilution of the buffer solution.
  • Another participant points out the need for concentration information for both components of the buffer solution.
  • A later reply clarifies that both acetic acid and acetate are at a concentration of 0.10 M.
  • Participants suggest using the Henderson-Hasselbalch equation, with a hint to calculate pKa from Ka.
  • One participant notes that while concentrations can be calculated, there may be a simpler approach to the problem that could be confusing if explained.

Areas of Agreement / Disagreement

There is no consensus yet on the best approach to solve the problem, as participants are still clarifying the necessary information and steps to take.

Contextual Notes

Participants have not yet resolved the confusion regarding the initial steps for calculating the pH, and there are unresolved aspects related to the dilution process and its impact on the buffer components.

n77ler
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Homework Statement


Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

Homework Equations


Ice charts
n= c x v
c= n/v

The Attempt at a Solution


I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
 
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You haven't given enough information to start. You need to know something about the concentrations of acetic acid (55 mL?) and acetate (45 mL?).
 
Sorry, they are both 0.10 M
 
Review the Henderson-Hasselbach equation. Hint: pKa = -log[Ka]
 
n77ler said:

Homework Statement


Buffer solution : CH_3COOH (55 mL) + CH_3COONa (45 mL)
Ka (CH_3COOH) = 1.76 x 10^-5

Calculate the expected pH of your buffer solution after it has been dilted by making 10 mL of buffer up to 100 mL with deionized water.

Homework Equations


Ice charts
n= c x v
c= n/v

The Attempt at a Solution


I've calculated the pH for other additions of strong acids and strong bases but I'm not sure how to start this one. Little bit confused... Just the first step would be a great help :)
the question is a little confusing due to the given volumes.i need help how to attempt the question.
 
As chemisttree already wrote: use Henderson-Hasselbalch equation. Start calculating concentrations of both acid and conjugate base. At this stage it will be simple dilution problem.

(in fact you can solve the problem without calculating these concentrations, but I guess explaining the shorter route will only confuse you more)
 

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