How can I prepare a 0.1M NaOAc buffer at pH 5 using titration?

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Discussion Overview

The discussion revolves around the preparation of a 0.1M sodium acetate (NaOAc) buffer at pH 5, focusing on the methods for achieving the desired molarity and pH through titration. Participants explore the calculations and considerations involved in buffer preparation.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant suggests creating a 0.2M solution of acetic acid and titrating it with sodium hydroxide to reach pH 5, expressing uncertainty about their pH calculations.
  • Another participant asserts that the pH of a 0.2M acetic acid solution is below 3, indicating a potential error in the initial calculations.
  • A different participant mentions that a 0.1M solution of acetic acid has a pH of approximately 2.88 and questions how to raise the pH without affecting the molarity.
  • One participant recommends checking worked-out examples at a provided link for guidance on buffer preparation.
  • A later reply suggests that titration could be a viable method to determine the necessary concentrations for achieving pH 5, emphasizing the importance of recording measurements and calibrating the pH meter.

Areas of Agreement / Disagreement

Participants express differing views on the pH calculations of acetic acid solutions, with some asserting errors in the initial claims. The discussion remains unresolved regarding the best approach to prepare the buffer at the desired pH while maintaining the correct molarity.

Contextual Notes

There are limitations regarding the assumptions made in the calculations of pH and the dependence on the specific concentrations used in the titration process. The discussion does not resolve the mathematical steps necessary for achieving the desired buffer conditions.

ReidMerrill
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For a lab I need to create a 0.1M solution of NaOAc buffer at pH 5
It's been a while since I worked with buffers. I'm struggling to find a way to get both the proper morality and proper pH.
My first though was to create a 0.2M solution of acetic acid and titrate it to pH 5 using sodium hydroxide. The problem is when I tried to calculate the pH of 0.2M solution of acetic acid I got a pH higher than 5 so I couldn't use sodium hydroxide to adjust the pH. I think this was a calculation error on my part though.

Any help would be greatly appreciated.
 
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Borek said:
Check this out: http://www.chembuddy.com/?left=buffers&right=toc

Yes, your calculation of pH is faulty, as pH of 0.2 M acetic acid is below 3.
I did some Google snooping and apparently the pH of a 0.1M solution of acetic acid is 2.88.

In that case, how do I raise the pH without lowering the molarity?
 
There are worked out examples at the link provided, why don't you check them?
 
ReidMerrill said:
For a lab I need to create a 0.1M solution of NaOAc buffer at pH 5
It's been a while since I worked with buffers. I'm struggling to find a way to get both the proper morality and proper pH.
My first though was to create a 0.2M solution of acetic acid and titrate it to pH 5 using sodium hydroxide. The problem is when I tried to calculate the pH of 0.2M solution of acetic acid I got a pH higher than 5 so I couldn't use sodium hydroxide to adjust the pH. I think this was a calculation error on my part though.

Any help would be greatly appreciated.
You COULD actually do the titration to determine, ultimately how to prepare your pH 5 buffer, as long as you carefully record how much of what concentrations of the solutions you used, as as long as you properly calibrated your pH meter before doing the titration. You should be able to figure how much sodium acetate is present once you reached pH 5. (This should be a beginner's lab exercise.)
 

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