Understanding pH Calculations for a Buffer Solution

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Discussion Overview

The discussion revolves around calculating the pH of a buffer solution composed of acetic acid and its salt, sodium acetate. Participants explore the application of the Henderson-Hasselbalch equation and the necessary parameters for the calculation.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a mixture of acetic acid and sodium acetate and expresses uncertainty about how to calculate the pH, suggesting they believe the answer is 4.89.
  • Another participant inquires if the Henderson-Hasselbalch equation has been studied, implying its relevance to the problem.
  • A participant asks if the Ka value for acetic acid is provided, indicating its importance for the calculation.
  • After confirming the Ka value, a participant explains the use of the Henderson-Hasselbalch equation and provides the formula for calculating pH, emphasizing the roles of the salt and acid in the buffer solution.
  • One participant expresses relief at finding the calculation easier than expected after receiving guidance.

Areas of Agreement / Disagreement

Participants generally agree on the use of the Henderson-Hasselbalch equation for calculating the pH of the buffer solution, but there is no consensus on the initial setup or the steps leading to the final answer.

Contextual Notes

The discussion includes assumptions about the applicability of the Henderson-Hasselbalch equation and the importance of the Ka value, which are not fully explored or resolved.

Who May Find This Useful

Students studying buffer solutions, those learning about pH calculations, and individuals interested in the application of the Henderson-Hasselbalch equation in chemistry.

jaredmt
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Homework Statement


A mixture containing 500ml of .1 M HC3H5O2 (acetic acid) and 500 ml of .1 M NaC3H5O2

what is the pH?

Homework Equations


can someone walk me through this? i know the answer is 4.89 but I am not sure how to get that. I am not even entirely sure how to set up the equation

The Attempt at a Solution


i tried this to start, but not sure if its right:
notations:
wa = weak acid
sa = strong acid
wb = weak base
sb = strong base
n = neutral

-wa----sb-------wb-----n
HAc + NaOH <> NaAc + H20

even if this is right, I am not sure where to go from here.
 
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Have you studied the Henderson-Hasselbach equation?
 
Just curious but are you provided with the Ka (acid dissociation constant) value for HC3H5O2?

For this case it's [salt] over [acid] (with Henderson-Hasselbach equation). Notice the acidic buffer there.
 
o sorry, the Ka = 1.3 x 10^-5
and yes we were taught the enderson-Hasselbach technique

i wish i could edit that into the 1st post but w/e
 
jaredmt said:
o sorry, the Ka = 1.3 x 10^-5
and yes we were taught the enderson-Hasselbach technique

i wish i could edit that into the 1st post but w/e
Ooooo and I'm wondering why I can't find that vital piece of information. The Ka means everything. Use this equation:

pH = pKa + log10 [salt]/[acid]

pKa = -log10 (Ka)

It's that simple =) Try it out!

You don't even have to write out the equation. NaC3H5O2 is the salt and HC3H5O2 is the acid. What you do need to know is that this is an acidic buffer solution.
 
Last edited:
ah ok that was easier than i thought, thanks
 

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